Life History and Fisheries of Atlantic Bluefin Tuna

NOAA Technical Memorandum NMFS-SEFSC - 370 {ffi3

Ilistorical Document: Life History and Fisheries of Atlantic Bluefin Tuna

Frank J. Mather, III Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543

John M. Mason, Jr. New York Department of Environmental Conservation Division of Marine Resources East Setauket. New York I1733

Albert C. Jones U.S. Department of Commerce, NOAA National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, Florida 33149

U.S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, Florida 33149 SH 11 .A2 s65 no -370 NOAA Technical Memorandum NMFS-SEFSC-370

Historical Document: Life History and Fisheries of Atlantic Bluefin Tuna

Frank 1. Mather, III Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543

John M. Mason, Jr.1 New York Department of Environmental Conservation Division of Marine Resources East Setauket, New York 17733

Albert C. Jones U.S. Department of Commerce, NOAA National Marine Fisheries Service Southeast Fisheries Science Center 75 Virginia Beach Drive Miami, Florida 33149

U.S. Department of Commerce Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration D. James Baker, Undersecretary for Oceans and Atmosphere

National Marine Fisheries Service Rolland A. Schmitten, Assistant Administrator for Fisheries

1 Formerly with Woods Hole Oceanographic Institution.

This technical memorandum is used for documentation and timely communication of preliminary results, interim reports, or special purpose information, and has not undergone external scientific review.

July 1995 NOTICE

The National Marine Fisheries Service (NMFS) does not approve, recommend, or endorse any proprietary product or material mentioned in this publication. No reference shall be made to the NMFS, or to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends, or endorses any proprietary product or proprietary material mentioned herein or which has as its purpose any intent to cause directly or indirectly the advertised product to be used or purchased because ofNMFS publication.

This report should be cited as follows:

Mather, FJ., J.M. Mason, and A.C. Jones. 1995. Historical document: life history and fisheries of Atlantic bluefm tuna. NOAA Technical Memorandum NMFS-SEFSC - 370: 165 pp.

Woods Hole Oceanographic Institution Contribution Number - 8986

AUTHORS' NOTE AND ACKNOWLEDGMENTS

This report is based on extensive studies of Atlantic blue fin tuna carried out over many years by the senior author. The report was prepared in the late I970s but not published. It is published now to provide a historical review of the biology and fisheries of blue fin tuna. based on knowledge available at that time. More recent studies have expanded the information base for bluefin tuna; however. that information is available, mostly in reports of the International Commission for the Conservation of Atlantic Tunas (ICCA T). Consequently, we have not attempted to include a review of that information in this document. We acknowledge financial and other support received from the following institutions and persons: the National Science Foundation, the National Marine Fisheries Service, the Sport Fishing Institute (now the American Sportfishing Association), the National Sea Grant Program, the Charles W. Brown, Jr. Foundation, the Lou Marron Science Fund, Mrs. Raymond J. Kunkel, Mr. William K. Carpenter. the Lerner Marine Laboratory, the Woods Hole Oceanographic Institution, and the Associates of the Woods Hole Oceanographic Institution. In addition ,to persons mentioned here and in the text, numerous individuals and fishery and research organizations contributed valuable information.

Copies may be obtained by writing:

National Marine Fisheries Service or National Technical Information Service Southeast Fisheries Science Center 5258 Port Royal Road 75 Virginia Beach Drive Springfield, Virginia 22161 Miami, Florida 33149 (703) 487-4650 FAX: (703) 321-8547 Rush Orders: (800) 336-4700

ii CONTENTS

I. INTRODUCTION I 3. Atlantic Oceanic Waters 29 4. Eastern Atlantic Islands 34 II. METHODS AND DEFINITIONS 2 a. Azores 34; A. Methods and Materials 2 b. Madeira 35 B. Definitions 2 c. Canary Islands 35 . I. Bluefin Tuna 2 5. Eastern Atlantic 36 a. Length 2 a. Northeastern Atlantic 37 b. Weight 3 b. Norway 37 2. Size-Age Groups 3 c. North Sea 38 3. Trap Fishery Terminology 3 d. Bay of Biscay 39 e. West Coast of Portugal 42 III. AGE AND GROWTH 5 f. West Coast of Morocco 42 A. Introduction 5 g. Ibero-Moroccan Bay Trap Fisheries 42 B. Methods of Determining Age and Growth and h. Trends in Eastern Atlantic Fisheries 46 Their Application to Bluefin Tuna 5 6. Mediterranean and Black Seas 46 1. Size Frequencies 5 a. Western Mediterranean 48 2. Counts of Marks on Hard Parts 5 b. Central Mediterranean 53 a. Scales 5 c. Eastern Mediterranean and Black Sea 63 b. Vertebrae 6 d. Summary 66 c. Otoliths 7 3. Release-Recapture Data for Tagged Fish 8 V. SPAWNING 68 C. Results 8 A. Introduction 68 1. Sizes of Fish at Determinable Ages 8 B. Definitions 68 2. Growth of Bluefm Tuna in Its First Year C. Criteria for Determining Seasons and Areas of Life 9 of Spawning, and Their Limitations 68 3. Growth of Young Bluefin Tuna 11 I. Presence of Ripe Adults : 68 4. Seasonal Changes in the Length-Weight 2. Presence of Pelagic Eggs and Larvae 69 Relationship of Large Bluefin Tuna 12 D. Spawning Areas and Seasons 70 5. Differential Growth of Males and Females 13 1. Mediterranean and Black Seas 70 6. Ultimate Length 13 a. General Information 70 7. Discussion 14 b. Specific Occurrences 70 2. Eastern and Central North Atlantic and the IV. DISTRIBUTION AND FISHERIES 15 South Atlantic 72 A. General Distribution 15 a. General Information 72 B. Development of the Major Fisheries 15 b. Specific Occurrences 73 C. Distribution and Fisheries by Areas 18 3. Western North Atlantic , 80 I. Introduction 18 a. General Information 80 2. Western Atlantic 18 b. Specific Occurrences 80 a. Newfoundland to Cape Cod 18 E. Relationships Between Environmental Factors i. Newfoundland 18 and Spawning Behavior 84 ii. GulfofSt. Lawrence 19 I. Introduction 84 iii. Nova Scotia 19 2. Mediterranean Sea 86 iv. Cape Cod to Maine 22 3. Eastern Atlantic 87 b. Cape Hatteras - Cape Cod a. Distribution, Objectives and Nature of (Coastal Waters) 25 Research 87 c. Atlantic Ocean Outside 200 Meter Contour b. Portugal 88 N of 35°N and W of 400W 27 c. Spain 88 d. Bahamas and Southeastern Florida 27 d. Morocco 90 e. Gulf of Mexico and Caribbean Sea 29 e. Other Eastern Atlantic Areas 91

iii 4. Western Atlantic 91 2. Western Atlantic 113 a. Introduction 91 a. Introduction 113 b. Gulf of Mexico 91 b. Large Fish 113 c. Straits of Florida 91 c. Medium Fish 124 d. East and North of the Bahamas 91 d. Small Fish 127 e. Northeastern United States 92 e. Very Small Fish 129 F. Feeding Activity During the Spawning Season 92 3. Trans-Atlantic and Trans-Equatorial G. The Spawning Act. 92 Migrations, and Atlantic Stocks 129 H. Maturity and Fecundity 92 a. Introduction 129 I. Age and Si:ze at First Maturity: 92 b. Trans-Atlantic Migrations 129 2. Fecundity 93 i. Giant Fish 129 3. Maximum Size at which Bluefin Tuna ii. Medium Fish 130 Spawn 94 iii. Small fish 130 I. Discussion and Conclusions 94 c. Trans-Equatorial Migrations 132 1. Mediterranean and Black Seas 94 d. Stock Identification 132 2. Eastern Atlantic 95 i. Biometric Studies 132 3. Western North Atlantic 95 ii. Biochemical Studies 132 4. Overall Situation 95 iii. Conclusions 132

VI. MIGRATIONS AND STOCK VII. DISCUSSION, RECOMMENDATIONS, IDENTIFICATION •.•...... •....•...... •...... •....96 AND CONCLUSIONS •.•..•....•.....•...... •.•..•...•...... 133 A. Introduction 96 A. Introduction 133 B. Methods and Materials, and Definitions 96 B. Age and Growth 133 1. Methods and Materials 96 C. Distribution, Migrations, and Spawning 133 a. Deductive Methods 96 1. Introduction 133 b. Methods Used Mainly for Identifying a Very Small Fish 133 Stocks 96 b. Small Fish 133 c. Methods Used Mainly for Studying i. Immature Individuals 133 Migrations , 96 ii. Mature Individuals 133 d. Development of Bluefin Tuna Tagging 96 c. Medium Fish 133 e. Summary of Bluefin Tuna Tagging d. Large Fish 133 Programs , 97 2. Western Atlantic 134 2. Definitions 97 a. Very Small Fish 134 3. Hypothetical Migration Model 97 b. Small Fish 134 C. Studies of Migrations and Stock Identity 98 c. Medium Fish 134 1. Mediterranean and Eastern Atlantic 98 d. Large Fish 135 a. Introduction 98 3. Eastern Atlantic and Mediterranean 135 b. Migrations Between the Mediterranean a. Very Small Fish 135 and the Eastern Atlantic 99 b. Small Fish 136 c. Migrations and Stocks within the c. Medium Fish 137 Mediterranean 104 d. Large Fish 137 d. Migrations and Stocks in the Eastern 4. Comparison 139 Atlantic 108 D. Identification of Stocks 140 i. Large and Medium Fish 108 E. Recommendations 143 ii. Small Fish III iii. Very Small Fish 112 VIII. BIBLIOGRAPHy ...... ••...... •...... •....•.....•..145 A. Introductory Notes 145 B. References 145

iv I. INTRODUCTION

The objective of this work is to ing less than 6.4 kg. Notwithstanding ment (National Marine Fisheries Ser- review and summarize available infor- the above regulation, the contracting vice, 1975, 1976) Canada, France, and mation on the fisheries, distribution, parties may grant tolerances to boats Japan have also put the ICCA T regula- and other aspects of the life history of which have incidentally captured blue- tions into effect (Caddy and Burnett the Atlantic bluefin tuna, Thunnus fm tuna weighing less than 6.4 kg, with 1976, Kume 1976, 1977). thynnus thynnus (Linnaeus 1758) (Fig- the condition that this incidental catch Whether these regulations were en- ure 1). The need for such a review is should not exceed 15% of the number acted in time, and are adequate to re- emphasized by the concern over the of fish per landing of the total bluefm store the Atlantic bluefm tuna fisheries status of the Atlantic bluefm tuna stocks tuna catch of said boats or its equiva- to their potential and former impor- and the recent enactment of measures lent in percentage by weight. tance, is questionable. It is certain, hoW- for the conservation of this species by Second - That as a preliminary ever, that better knowledge of the life the International Commission for the step, the contracting parties that are history of the bluefm tuna is a prerequi- Conservation of Atlantic Tunas actively fishing for bluefin tuna site to effective management of its fish- (ICCAT). (Thunnus thynnus thynnus) or those that eries. By general consensus, knowl- The wastefulness of harvesting Atlantic bluefm tuna at extremely small sizes was recognized intuitively by d' Amico (1816, cited by Pavesi 1887). Sicilian laws of 1796 and 1801 prohibited the catching of small bluefm tuna (Avolio 1805 in Parona 1919). This restriction was apparently dropped during revisions of Italian fishery regulations in 1877 and 1882 (Pavesi 1887), but a minimum size limit of 60 cm was imposed in 1927 (Mussolini and Belluzzo 1927). In the 1960s, a minimum size limit of 90 cm was in effect in Italy (Sara 1968, Miyake 1976, Figure 1. Atlantic bluefin tuna (Thunnus thynnus thynnus). Maldura 1965). The effect of harvesting bluefin incidentally catch it in significant quan- edge of stock identity and migratory tuna at small sizes was estimated theo- tities shall take the necessary measures patterns is of prime importance. retically by Shingu et al. (1975) and to limit the fishing mortality of blue fin The aspects of the fisheries and empirically by Mather (1974). Both tuna to recent levels for a period of one life history herein discussed include: works indicated that the capture of one year. At the 1975 meetings of the age and growth information; catch sta- thousand tons of young bluefin tuna ICCA T Commission, this second item tistics; size, sex, and age composition precluded the subsequent capture of was extended for an additional two of the landings in various areas; spawn- many thousand tons oflarger individu- years, with provision for its review at ing and development; migration; and stock identification. Environmental pa- als. the 1976 meetings ofthe ICCA T Coun- Action in 1975byICCATinregu- cil. rameters and their possible influences lating the bluefin tuna fisheries finally The member nations are respon- on the distribution, migrations and recognized in principle the need to man- sible for enforcementofICCA T regula- spawning of the species are also con- age the fisheries for this economically tions within their territorial waters. For sidered. Hypotheses on the migrations important species. The regulations the United States, the Atlantic Tunas of bluefin tuna and stock identity are which became effective August 10, Convention Act of 1975 empowered discussed. Finally, we state our own 1975, are as follows (Miyake 1975): the Secretary of Commerce to imple- conclusions in regard to these matters First - That the contracting par- mentregulations established by lCCAT. and make some recommendations for ties take the necessary measures to pro- The National Marine Fisheries Service future research. hibit any taking and landing of blue fin (NMFS) drew up a set of regulations, tuna (Thunnus thynnus thynnus) weigh- and is responsible for their enforce- II. METHODS AND DEFINITIONS

A. METHODS AND MATERIALS viduals concerned with the Atlantic B. DEFINITIONS Personal research by the authors bluefm tuna in many areas and several 1. Bluefin Tuna during 1950-1976 has produced much nations. An important additional source of The subject of this paper is the of the knowledge which is summarized information was a thorough search of Atlantic bluefin tuna, Thunnus thynnus herein. Extensive additional informa- the literature. This was most intensive thynnus, as distinct from the southern tion was obtained from the literature, by participation in meetings, and through correspondence and conversations with scientists, fishery experts, and fishermen. The authors and their colleagues obtained a great mass of data and information on the species and its fisheries directly. They examined the landings and often observed or participated in the operations of various commercial and recreational fisheries over a great geographical range. They also participated in many exploratory fishing cruises of U.S. and foreign research Fork Length vessels. The Cooperative Game Fish Tag- Figure 2. Fork length measurement. ging Program of the Woods Hole Oceanographic Institution (a joint program with the National Marine Fisher- ies Service since 1973), initiated by the at the initiation of our studies and has bluefin tuna, Thunnus maccoyii senior author in 1954, has provided been continued since then to the extent (Castelnau 1872) and the Pacific blue- much of the information on migrations that time has permitted. This experi- fin tuna, Thunnus thynnus orienta/is and mortality rates of Atlantic bluefm ence has enabled us to locate many (Temminck and Schlegel 1844). The tuna. Exchange of information and co- important and little known references. ranges of the Atlantic and the southern operation with marking programs of Our extensive contacts and data bluefms overlap off South Africa and other nations has been extensive. sources, increasing over the years, have in the South Atlantic, whereas those of Also, much information has been enabled us to maintain close connec- the Atlantic and the Pacific bluefins are obtained through participation in meet- tion with the entire Atlantic bluefin apparently separate (Gibbs and Collette ings of a variety of groups. These in- tuna situation. 1967, Talbot and Penrith 1968, Fisher- clude international regulatory agencies In the course of our investigations ies agency of Japan 1974, 1975, 1976, and advisory groups, such as ICCA T, it became increasingly apparent that 1977). the Panel of Experts for the Facilitation this species cannot be studied success- Throughout this report, the terms of Tuna Research ofthe Food and Ag- fully on a piecemeal or limited area Atlantic bluefin tuna, bluefin tuna, blue- riculture Organization (FAO) of the basis. Our approach, therefore, has been fin, tuna, fish, and individual refer to United Nations, and national, regional an attempt to observe and describe the Thunnus thynnus thynnus unless other- and state fishery agencies. We have species and its fisheries over its entire wise identified. also attended numerous meetings of geographic range and during each stage non-governmental research and fish- of its life cycle. Our methodology has a. Length ery groups or associations. been a combination of original research The most widely used measure- Further knowledge was obtained and a review of the findings of other ment oflength forbluefin tuna over 12 by correspondence and conversations investigators in all the nations con- cm is fork length (FL). This is the with representatives of agencies of the cerned with Atlantic bluefin tuna. straight line length, measured by cali- types mentioned above, and with indi- pers or equivalent instruments, from

2 Table 1. Size-age groups used to discuss much ofthe biological and fisheries data correspond as closely as possible to for Atlantic bluefm tuna in this report. sizes and estimated ages at which the Group Length Weight Approximate Age migratory and distributional patterns (em) (in) (kg) (Ibs) (years) of the species undergo distinct changes Very small <50 <20 <2.5 < 5 o (Mather I964b). The ages for the respective sizes are from Mather and 2.5 ~32 5 -70 Small 50-120 20-48 I - 4 Schuck (1960). These size groups were Medium 120-185 48-76 32 - 122 70 - 270 5-8 set up on the basis of data from the summer fisheries in the northwestern Large or Giant >185 >76 > 122 >270 >8 Atlantic and the spring fishery off the Bahamas. They appear, however, to be reasonably applicable to bluefm in the eastern Atlantic and the Mediterranean the snout (tip of upper jaw) to the pos- the fish have been butchered. Conver- Sea. sion factors for obtaining round weights terior medial margin of the caudal fin 3. Trap Fishery Terminology from weights in the various other con- (Figure 2). In this paper, length mea- Specialized terms have been used ditions are available in the literature surements exceeding 12 cm are fork to describe the bluefin tuna trap fisher- and at the Woods Hole Oceanographic lengths unless defined otherwise. An ies ofthe eastern Atlantic and the Medi- Institution. alternative method of measuring fork terranean Sea. Since these terms are Weights of individual fish and av- length is with a tape and following the often misunderstood or poorly trans- erage weights of fish are recorded in lateral contour of the body. Lengths lated in the literature, an explanation of kilograms, unless otherwise stated. measured by this method have been them seems desirable. Weights of landings and catches (of referred to as tape lengths, curved The true bluefin tuna traps are very numerous fish) are recorded in metric lengths or flank lengths. The slope of a large, complex installations set at spe- tons unless otherwise stated. linear regression which Schuck and cial locations to harvest runs (periodic Mather fitted by inspection to a plot of 2. Size-Age Groups migratory passages) related to the straight lengths against curved lengths Much of the biological and fisher- spawning of these fish. "Arrival" fish for each of a series of western north ies data for the Atlantic bluefin tuna are essentially fat, maturing individu- Atlantic bluefm tuna from 35 to 270 will be discussed in terms of the size- als, generally traveling eastward in late cm long indicated that the straight length age groups shown in Table 1. The lim- April, May, and Jiune."Return" fish are was 0.958 times the curved length. Sev- its of these groups were selected to essentially lean, spent individuals, general other authors have published con- version factors for these parameters. Of course this relationship would vary slightly with the length-girth (or length- Table 2. A glossary of some ofthe more important tuna fishery terms in English, weight) ratio of the fish. French, Italian, Portuguese, and Spanish. The lengths of juvenile specimens less than 12 em long and of larvae are English French Italian Portuguese Spanish usually measured in standard length (SL). This is the length from the snout True Tuna Trap Madrague Tonnara' Armacoa Almadraba to the end of the vertebral column. In Thonaire' this paper, length measurements of blue- Minor Tuna Trap Petite Madrague Tonnarella Almadrabilla fm tuna less than 12 em long are stan- Thonaire Mixte dard lengths unless defined otherwise. Arrival Arrive Corsa Direito Derecho b. Weight Course Arribada Weight data for fish are presented in this paper in terms of round, whole, Return Retour Ritorno Revez Reves or live weight (the weight of the entire Genetic Gcnetique Genetico Genetico fish) unless otherwise stated. In some fisheries, it is necessary to collect weight Erratic Erratiquc Erratico Erratico data for fish in the condition in which they are sold. This may be in several I The words thonaire and tonnara are also used locally for other gears which catch tunas forms depending on the extentto which or tuna-like fishes.

3 eraIly traveling westward in July, Au- em Atlantic coasts of Portugal and Roule (1914a, 1914b) propOsed gust, and early September. Some of the Spain, many traps were altered to fish the terms "genetic" for maturing blue- younger spawners, which have not yet for each season, and in this way they fin tuna, and "erratic" for those which discharged their eggs, are sometimes fished both runs. had spawned and whose behavior was taken with the return fish. The arrival SmaIler and less important traps dominated by search for food. TheSe fish are not only more robust than the take bluefin tuna throughout much of terms occur in many works on these return ones, but their flesh is fattier and the year, but these fish are mainly im- fisheries. A brief glossary of some of usually commands a higher price. mature individuals or larger ones which the more important terms, in English, In most areas, traps· were fished have completed their spawning cycle French, Italian, Portuguese, and Span- for only one run - either as arrival or and .are more widely dispersed, pre- ish is listed in Table 2. return traps. However, along the south· sumably in search of food.

4 DI. AGE AND GROWTH

A. INTRODUCfION evidently the first to study the growth The relative merits of these meth- oflarger bluefin tuna by this method. ods were extensively discussed at the Knowledge of the age-size rela- They traced the growth of young in- "conference d' experts pour I' examen tionship is not only important from dividuals taken off Long Island, New des methodes scientifiques et tech- the biological viewpoint but is also York, in the summers of 1938 and niques a appliquer a I'etude des essential for effective management 1941 by analyzing their length fre- po issons de la famille des Thonides" of a fishery. Until recently, there has quencies. They established the age in (hereafter referred to as "Conference been general agreement on the sizes years of each size group by counting of experts") held at Madrid and Cadiz, of Atlantic bluefin tuna at ages up to annuli on scales. Spain, 16-22 May 1932 (Anonymous 12-14. Preliminary results for ages Buser-Lahaye and Doumenge 1932b), and by others as cited here. up to 26 have been presented in 1975 (1954) and Doumenge and Lahaye and 1976, but these are controver- (1958) likewise analyzed length fre- a. Scales sial. quencies to estimate the ages of small Age determinations from scales bluefin tuna caught off the Mediter- are based on counting the "checks" or areas where two or more circuli B. METHODS OF ranean coast of France during 1953 are close together, instead of being DETERMINING AGE AND and 1954. They used Sella's (1929a) more widely and evenly spaced as GROWTH AND THEIR data, however, to establish the esti- they are on most of the scale's sur- APPLICATION TO BLUEFIN mated age of each size group. face. TUNA More extensive studies of the summer growth of western Atlantic Corson (1923a, 1923b) presented 1. Size Frequencies bluefin tuna, using counts of annuli the first age determinations for Atlan- Age groups show up as modes on hard parts as well as size frequen- tic bluefin tuna of which we have when the sizes of sufficient numbers cies, were presented by Mather and knowledge. These were based on of bluefin tuna are plotted. These Schuck (1960). scales taken from a small number of modes are usually distinct for small Furnestin and Dardignac (1962) young fish caught off Long Island, individuals (up to 125-150 cm long), were the first authors to trace the New York, in September 1923. He but become less distinguishable with growth of T thynnus thynnus through used scales from the posterior part of larger fish. The length-weight ratio most of the first two years of its life. the fish, having found those from the oflarge bluefin fluctuates greatly with They used size frequencies of young shoulder to be unreadable because of the seasons (Tiews 1963). Therefore fish taken off the Atlantic coast of streaks and globules of oil within length measurements are more suit- Morocco, where, after attaining a them. able for size frequency analyses than length of about 32 em, they are avail- At the "Conference of experts" weights. Growth may be estimated able throughout the year. (Anonymous 1932b), F. de Buen and from the progression of modes in Tiews (1960) used the frequen- Sella said that scales did not furnish plots of size data for consecutive time cies of eye diameters, which he as- intervals. sumed to be related to the age of the Size-frequencies were evidently fish, as well as to its length, to esti- used, although the methodology was mate the ages of large bluefin tuna not described, by d' Amico (1816, in caught in the North Sea in the sum- Heldt 1930) and Bourge (1908, in mer and fall of 1959. Roule 1917), in estimating the sizes of juvenile Mediterranean bluefin 2. Counts of Marks on Hard tuna in their first four months of life. Parts Piccinetti and Piccinetti-Manfrin Ages of blue fin tuna have been (1970) presented a more detailed and estimated by counting marks, usu- precise study of their growth through ally called annuli, which were thought this period, describing the methods to have been laid down annually, on they had used. certain hard parts of the fish. The Westman and Gilbert (1941) and parts used included scales, vertebrae, Figure 3. Bluefin tuna vertebra Westman and Neville (1942) were and otoliths (Figure 3). showing two annuli.

5 interesting infonnation on the age of Mather and Schuck (1960) esti- other experts discussed the use of the bluefin tuna, but Frade showed mated ages of 0-4 years from scales vertebrae for age determination. Sev- that growth lines were clearly indi- of bluefin tuna taken off the north- eral methods of preparing vertebrae cated on scales of young individuals. eastern United States during several for examination were described, and The experts concluded that scales summers. They relied more heavily it was noted that they could be exam- were not useful for determining on length frequencies for studying ined without special preparation. He growth in this species, except for the grow~h of young individuals, described three instruments which he young individuals. however, and on vertebral annuli for used in the study of vertebrae and Spagnolio (1938) estimated ages the older ones. These authors used stated that the annuli were generally of from 3 to 6 years from scales of scales from the general part of the better defined in vertebrae from the bluefm tuna caught in traps off south- tuna's body where Westman and Gil- caudal trunk. Heldt reported that, in ern Italy and northeastern Sicily. She bert (I 941) and Westman and Neville each of five blue fin tuna of different presented illustrations of these scales (I942) collected theirs. They made sizes which he had examined, the but did not report the sizes of the impressions of the scales on cellu- number of annuli on each of the ver- fish. She concluded that readings loid (Arnold 1951), and counted an- tebrae was the same. He also noted from scales should be checked against nuli on magnified projections of these that double rings, which should not readings from vertebrae of the same impressions. be counted as two years, sometimes individual. She maintained that if the None of the above authors used occurred. Sella and F. de Buen main- method were validated, scales would the large and thick scales of the corse- tained that the vertebral rings repre- be preferable to vertebrae for deter- let for age determinations, but F.S. sented years of age, but the latter mining ages of small bluefin tuna, up Russell mentioned (personal commu- noted that, because of the time of to 40-58 kg or 5-6 years of age, since nication) that he had found a pos- spawning, the first ring did not cor- scales were easier to collect and to sible method of determining ages respond exactly to one year. Frade examine than vertebrae. Spagnolio from these scales. He found that they reported finding 16 vertebral annuli used scales from the caudal and lat- were built up of lamina, like the pages for a 263 em fish, which exceeded eral parts ofthe body, rejecting those in a book, which might represent the maximum age reported by Sella from the corselet because they were years of growth. These lamina could (1929a). too thick and opaque. The scales be separated after the scales had been Several workers reported on the which she used were preserved in soaked in a weak solution of acetic growth of blue fin tuna from different formalin, and later were soaked in acid. areas as determined from readings of water or an alcohol solution or glyc- The most important use of scale vertebral annu Ii in the period 1956- erine before examination. She found readings in aging bluefin tuna has 1962. These include Hamre (1958, no marked advantage in using either been in validating determinations 1960) (Norway), Rodriguez-Roda of the last two fluids instead of wa- made by other methods (Westman (1960) (Spain), Vilela and Pinto ter. and Neville 1942, Mather and Schuck (I 958), Vilela (1960), and Frade and Westman and Gilbert (1941) and 1960). Vilela (1962) (Portugal), and Mather Westman and Neville (1942) used and Schuck (1960) (northeastern readings of annuli on scales, as well b. Vertebrae United States). Mather and Schuck as analyses of length frequencies, to F. de Buen (I 925) estimated, by used the technique ofGaltsoff(l952) detennine ages of young (1-7 year counting its vertebral rings, that a to stain many of the vertebrae which old) bluefin tuna taken off Long Is- male bluefin tuna 206 em long (from they used for age determinations. land, New York, during the summers snout to tips of caudal) and weighing Rodriguez-Roda (1964a) presented of1938 and 1941. These authors also 119 kg was 12 years old. This fish thorough mathematical interpreta- offered tentative age determinations was caught July 4, 1923, in the tions of his 1960 results. from scales for a few much larger Barbate trap near Cadiz, Spain. Butler (1971, 1975) counted the bluefin tuna, up to 250 em and 275 Sella (1929a) presented mean rings in the vertebrae ofJarge bluefin kg, with an estimated age of about I 8 lengths and weights of Mediterranean tuna taken in Canadian waters in 1966 years. They used carefully selected bluefin tuna for ages I-14, as esti- and in 1974 and estimated their ages thin and round scales from the side mated by counting the rings in the as II to 22 or more years. Myklevoll of the body, just below the lateral centra of vertebrae. This was the first used this method to detennine the line in the area below the base of the study which described the growth of ages of bluefin tuna taken in Norwe- second dorsal fin. Projected impres- bluefin tuna through most of the size gian waters in 1974 (Caddy and But- sions of the scales facilitated their range ordinarily encountered. ler 1976). These estimates ranged readings of those with more than five At the "Conference of experts'~ from 14 to 2 I years. annuli. (Anonymous 1932b), Sella and the

6 Butler and MyklevoIl were the difficulties encountered in extracting rameters for von Bertalanffy growth first investigators to estimate the ages otoliths, Frade (1925) described pro- equations for males and females, us- of significant numbers of blue fin tuna cedures for their relatively rapid re- ing their data for fish of ages 10 or more than 14 years old. moval, and the nature of the growth greater and Mather and Schuck's Berry et al. (1977) discussed in zones on them. These descriptions, (1960) results for fish of ages 1-4. great detail the techniques of aging accompanied by excellent illustra- Their work was the first to indi- bluefin tuna by reading annuli on tions, suggested that this was a prac- cate different growth rates for the vertebrae and otoliths. They de- tical method of age determination. two sexes. Butler et al. (1977) repro- scribed methods of storing, staining At the "Conference of experts" duced the above material with the and examining vertebrae, and their (Anonymous 1932b), however, Frade addition of preliminary age data from interpretation of the markings on reported that, although he had found the otoliths of 60 large bluefin taken them. They found that immediate zones of growth in thin sections of in Canadian waters in 1976, and pre- freezing and freezer storage produced otoliths, he was not sure that these sented some modifications of the better results than the other methods sections included all of the years of Nichy and Berry (1976) and Caddy of preservation which they tested. Im- growth. He attributed his uncertainty and Butler (1976) techniques. mediate staining and reading, how- to the irregular shape of the otoliths. Berry et at. (1977) discussed the ever, was probably the most satisfac- The experts concluded that growth removal, storage, measuring, mount- tory procedure. They noted that stain- zones were laid down on otoliths, but ing and sectioning of otoliths. They ing time varied with the size of fish, that it was difficult to assign absolute described the sections and their in- and that the inner rings, particularly ages by counting these zones. They terpretation of the markings on them. in large fish, stained before the outer therefore recommended thatthis tech- They found that, at ages greater than ones. nique be used mainly to confirm age 10 or 11, hyaline bands occurred in Their interpretation of marks on determinations obtained by other pairs which represented a single an- vertebrae was complex. It involved means. nular zone. ridges, grooves, fimbriated lines, and Frade and Vilela (1962) referred They discussed definitions of annuli stained and unstained rings. They to age determinations from otoliths on vertebrae and otoliths, and pro- noted that several stained rings might by Frade (1950), but we have not posed the foIlowing tripartite hypoth- occur early in the staining process seen the latter work. No further ref- esis: within an annular zone, and thatthese erences to Frade's early work with a) Major discernible markings on ver- might coalesce in various ways as otoliths have come to our attention. tebrae and otoliths of Atlantic blue- staining progressed. The next attempt to determine fin tuna do ll.Q1have to be pre- Berry et at. (1977) did not in- ages of bluefin tuna from otoliths sumed to be annuli. clude size-for-age data or age data was by Nichy (Nichy and Berry b) Within each year of life, multiple for individual fish, but they presented 1976). They developed techniques for markings are successively formed extreme and average vertebral ages, estimating the ages of bluefin tuna on vertebrae and in otoliths. These determined from readings of verte- similar to those ofFrade (1925). They multiple markings may appear in bral annuli, for bluefin tuna in vari- used otoliths from large individuals prepared specimens of vertebrae ous weight ranges. They tentatively caught off Prince Edward Island in and otoliths as irregular combina- recommended the use of vertebrae the GulfofSt. Lawrence, Canada, in tions. Single markings that repre- for estimating ages up to about 10 1974. Caddy and Butler (1976) clas- sent the end of a year of life (an- years for this species. sified large bluefin tuna taken in Ca- nuli) may be distorted by varia- From 1932 until 1974, counting nadian waters in 1974 and 1975 by tions of the within year multiple vertebral annuli was generally re- year classes, using Nichy and Berry's markings. garded as the most satisfactory techniques and some of their deter- c) Annuli may be deciphered by con- method of aging large Atlantic blue- minations in addition to their own. sidering the nature in which they fin tuna. They did not report the sizes of these form and by interpreting the varia- fish. tions that may exist within and be- c. Otoliths Caddy et al. (1976) present the tween individual prepared samples. ]be use of otoliths in determin- most complete study available on the Berry et at. (1977) did not present ing ages of T. thynnus thynnus was growth of blue fin tuna as determined age data based on readings of annuli first investigated in the 1920s, but from otoliths. They used this method on otoliths. important results did not appear until to determine the ages of large indi- 1975. viduals (age 10 and over) caught in 3. Release-Recapture Data for Tagged Fish Despite the fact that F. de Buen Canadian waters during the summer (1925) had been discouraged by the and fall of 1975. They calculated pa- When size data at release and recapture of a given fish are avail-

7 able, its growth during the period at Sella (1929a) presented the first information of the sizes of fish of· liberty is established. If age at the important study of the age and growth ages 1-4 taken during the summers time of release can be determined, of bluefin tuna. This was based on of 1938 and 1941 off Long Island, age at the time of recapture can like- counts of annuli on vertebrae from New York, and sizes based on small wise be calculated. Positive age and more than 1,500 bluefin tuna caught samples or individual specimens, for growth information thus obtained can in June, during the spawning season. young of the year and for various provide a valuable check on estimates The individuals whose ages were as- ages of 5 years or more. based on indirect methods (Mather sessed as 3 or more years had been Several additional works on the 1980). taken off Tripolitania (western age and growth of blue fin tuna taken Libya). Sella noted that these results in various parts of the Atlantic Ocean did not differ noticeably from those were published between 1958 and C.RESULTS for bluefin tuna taken in other parts 1962. Tiews (1963) plotted the sizes 1. Sizes ofFish at Determinable of the Mediterranean. He assessed for ages obtained by Sella (1929a), Ages ages of I and 2 years for individuals Westman and Gilbert (1941), Hamre which had been captured in the (1960), Vilela et al. (1960), Tiews The first objective of most age Adriatic Sea, since fish of these sizes 1960), Rodriguez-Roda (1960), and and growth studies is to determine were not available off Libya. He pre- Mather and Schuck (1960) (Figure the mean sizes of fish at each year of sented his results in terms of mean 4). As Tiews observed, the results of age for which this is possible~ Ideally length and mean weight for each year t.~ese studies, using material from sev- the sizes should be determined at one of age from I through 14. eral widely separated areas, are re- year intervals after the date of spawn- Westman and Gilbert (1941) and markably similar. ing. This was done by Sella (1929a) Westman and Neville (1942) pro- Rodriguez-Roda (1960, 1964a) and Rodriguez- Roda (1960, 1964a), duced the first important informa- presented the following formula for but most other investigators have tion on the growth of bluefin tuna back-calculating the fork length of a been limited to seasons in which suf- taken in the western Atlantic. Their bluefin tuna at ages previous to that ficient material was available. works provided well supported of its capture: 1= 17.88 +v/v(L-17.86) where: L = fork length in cm of the fish,

LlIIlllb pen 117 Sella (191'a) Welpt pvea 117 Sella (I 919a) o Lea&tb &lVe. 117 Tie ••••(1960.) V = radius in mm of the fourth or fifth • IAnIlfb pili 117 W•• tlIIaa aad CUbert (1941) 'V lAn&tb &Iv'. 117 Rodr1cwa.Reda (1960) precaudal vertebra, o LMIlfb amn 117 Hamre (1960) + Lenlltb &Iv- 117 Matb ••. aad S~bud< (1960) I = fork length in cm of fish at age x, )( LMlllb pven 117 VIIeIa at al. (19'0) /), WeI&bl &"'''' 117 Maltier and S~ud< (1960) and

1(0 v = radius (mm) of vertebral ring cor- z,{0 JOO responding to age x.

220 The back-calculated lengths were 150 considerably less than those obtained 200 directly for fish of the same ages. 100 ! ISO This was due in part to the fact that ::;; the vertebral rings were laid on dur- j Isa ~ ing the winter, but the direct age de- ~ ~ terminations were made from mate- i!! 100 rial collected in late spring and early s: summer. 50 Rodriguez-Roda presented revised size- for-age data (1969c) and o the following von Beltalanffy equa" 60 tion for the relation between age and 2 J , 5 , 7 , 9 10 11 11 13 " size: Age (years) I, = 355.84 (I_e·Il09(, + 089»

Figure 4. Sizes for ages as estimated by various authors (Tiews ]963).

8 Caddy et al. (I976), using otoliths Table 3. Growth and sizes of three tagged fish recaptured after periods of 13-14 from 225 large (over 220 cm long years at.1iberty. and 230 kg in weight) bluefin tuna Return Release Years at Recapture taken in Canadi~n waters in the sum- Number Length Age" Liberty Age Length Weight mer and fall of 1975, produced pre- (em) (years) (years) (em) (kg) liminary size for age data for fish up to 15 years old. They also calculated I 8.8 13 21.8 279 288 the following parameters for von 2 2.2 14.1 16.3 256 397 Bertalanffy growth curves (Figure 3 2.2 13.1 15.3 251b 329 5) for males and females:

Males Females a Assuming birth date June 1 (Richards 1976) and ages as estimated by Mather and Schuck 1960. K 0.134 0.116 b Estimate coinciding with modal size of21 fish caught on same longline set.

277.315 C Lm 286.64 Measurements converted to "caliper" length from "tape" length, assuming: caliper length = .958 tape length. t 0.3278 0.7999 ,Additional growth and size at age data have been obtained from the lengths at release and recapture for tured fish were not determined, the Berry et al. (1977) did not pro- three tagged fish which had been at agreement between results obtained vide size for age data, but they pre- liberty for periods of 13-14 years. mainly by direct methods and those sented age ranges and average ages (Table 3) (Mather 1980). Points cor- obtained from counts of age marks for selected weight ranges of blue fin responding to these sizes have been on otoliths is good. tuna captured off Massachusetts in plotted with the growth curves of The results of some of the more im- 1975 (Table 5). Butler et al. (1977) (Figure 5). All of portant studies of the sizes at ages of the points lie very near the curve of 2. Growth of Bluefin Tuna in Its Atlantic bluefin tuna are shown in Butler et al. (1977) for male bluefin. First Year of Life Table 4. Although the sexes of these recap- There has been much interest in determining the growth of the bluefin tuna during its first year of life, since this information is a prerequisite for validating the determinations of all older ages. Data on this subject, 300 1 ~ 0_0.-2 starting with the early observations 2. a_a-a-%- (a) .. ~-.-...-..- --; of d' Amico (I 816) have been reca- ...... •- ~!-.---{.) pitulated in detail by Scaccini et al. /"'-Femoles (I 975). The less extensive data from - 200 0'- the eastern Atlantic (Fumestin and ~ }J" p,a' Dardignac 1962) and the western At- 0' lantic (Rivas 1954, Mather and ~"o" , "- Schuck 1960) are in good agreement - , -' - from YOlller and Schuck 1960 with those from the Mediterranean. ~ 100 The growth in weight of larval and small juvenile bluefin (up to 1400 g, or about four months of age) spawned in the central Mediterranean o 20 has been described by Piccinetti and A~e (Vears) Piccinetti Manfrin (1970) (Figure 6). These authors estimated growth by Figure s. Fits ofvon Bertalanffy growth curves to mean fork length at age (as assuming that the largest individuals determined from otolith readings~ f.or n:t~I_eanti female bluefm tuna taken in in each collection made as the season Canadian waters in 1975 (bracketed values omitted). Mean sizes at age (series progressed represented the group combined) from Mather and Schuck' (I 960) for ages 1-4 (closed squares) were which was hatched earliest (about used in fitting both curves (from Butler et a!. 1977). Points in circles represent June 15). Thus it is possible that their lengths of three tagged fish at ages when recaptured.

9 Table 4. Sizes of Atlantic bluefin tuna at ages as detennined by various authors. Rodriguez- Westman, Mather, Caddy Sella Hamre Roda Vilela Neville Schuck et al. 1976* 1929a 1960 1969 1960 1941 1960 Males Females Age (em) (kg) (em) (em) (em) (em) (em) (em) (em)

I 64 4.4 55.3 65.0 57 2 81.5 9.5 79.0 85.0 77 3 97.5 16 116.2 105.2 95 4 118 25 130.1 120.5 117.6 114 5 136 40 135 146.9 136.0 147.8 133 6 153 58 153 165.1 146.9 148.3 149 7 169 76 166 178.1 163.9 157.5 163 8 182 95 180 192.9 187.2 177 9 195 120 195 206.5 196.1 190 10 206 145 207 220.3 217.7 201 11 216 170 221 221.5 223.0 223 12 227 200 228 244.0 232.8 231 13 239 235 239 246.0 239 14 254 280 245 15 250 238 16 254 242 17 258 244 18 262 246 19 266 248 20 270 250 21 273 252 22 275 255 23 276 257 24 278 258 25 279 259 *Estimated from curves (Figure 5).

1400 Table S. Age ranges and average ages for selected weight ranges of bluefin 1200 tuna captured off Massachusetts (Berry et aI. 1977). ~ 1000 ~ Weight Age Average •... Range Range Age ::t: 800 ....~ (kg) (years) (years) ~ 600

136-181 6- 9 7.3 400 181-226 8-10 8.6 227-272 8-14 11.1 200 272-317 12-14 12.7 318-362 13-17 14.9 15/V I/VI 15/vI I/VII IS/VII IIVIII IS/VIII IIIX IS/IX I/X 15/X 11"1 DATES Ages detennined by counting vertebml Figure 6. Growth in weight of bluefin tuna collected in Sicilian waters in their annuli. first months of life (Piccinetti and Piccinetti Manfrin 1970).

10 results apply to the fastest growing, rather than the average, individuals. 120 Rivas (1954) and Mather and Schuck (1960) presented very simi- 100 I- lar curves of estimated linear growth :J: C!l for the first eight months of life of ~ a: 80 l- bluefin tuna collected in the western ll) North Atlantic. Mather and Schuck's ~ u curve (Figure 7) was based on a lim- I 60 :J: ited number of measurements, inchid- I- C!l ing those of Rivas, from various ar- Z '".J eas .along the Atlantic coast of the 40 cr'"' United States and in the Gulf of ...a Mexico. The date of spawning was 20 assumed to be May 15. Although spawning probably occurs earlier in the western Atlantic than in the Medi- Ii 0 :: o 1 0 Ii 2 0 terranean (see Section V), the estimated mean sizes attained by the CALENDAR MONTHS AND YEARS OF AGE (BIRTH IS ASSUMEO TO OCCUR IN MID-MAY) young of the year by mid-October Figure 8. Estimated growth of young bluefin tuna. Broken lines indicate estimated are about the same in both areas-38 lengths in periods for which data are lacking. The lower scale shows ages cm or 1,100 g. Data for age 0 blue fin assuming that hatching occurs at mid-May (Mather and Schuck 1960). caught off the Atlantic coast of Mo- rocco (Furnestin and Dardignac 1962, Aloncle 1964) are similar. Individu- als taken in the first half of October In all three areas, growth is ex- western Atlantic fish are about 50 were 31 to 34 cm long, inNovember, tremely rapid in the spring, summer cm long, according to Furnestin and 39 to 43 cm, and at the end of De- and early fall, and considerably Dardignac (1962) and Mather and cember, 44 to 45 cm.· , slower during the first winter of life. Schuck (1960). Larger sizes are re- At twelve months of age,· eastern and ported for I-year-old tuna by Rodriguez-Roda (1960) for eastern Atlantic fish (55 cm) and Sella (1929a) for specimens from the Medi- 20 terranean Sea (64 cm).

3. Growth of Young BluefinTuna

o 40-I- Westman and Seville (1942) o. 0 ::J:: o 0 were the first to show that young ~ I~ 35 :'" cr> •...... • ... bluefin tuna grow much more rap- ::> !!! !:! .~O 0 + to++ CI "V .-. ~ 30::1 idly during the summer than during III 0d' •• ::J:: •• 0 '"•... the winter. They reached this conclu- <.>'" Z 2~ '"! sion by tracing the growth of young I 10 •... ::J:: z fish taken off Long Island, New York, \; 20 '"<.> Z I ::J:: through the period July I~October .J •... '" 16, 1941, from length frequency data. cr'" I~ ~ ~ 5 o NEW JERSEY- CAPE COD '".J Mather and Schuck (1960) stud- + MARYLAND-CAROLINAS \0 ~ • MIAIIII AREA ...o ied this matter in greater detail. Their • GULF OF MEXICO 5 data included some specimens taken '" during both summer and winter in

o NOVElli E feE B[R ",.NUAIIIY 0 their first year of life (age 0), but data were available for ages ]-4 for the period July-October ]6 only. The Figure 7. Lengths of bluefin tuna less than 50 cm long (young of the year) growth rates in the latter period were collected in the western Atlantic and the Gulf of Mexico. The curve of estimated very rapid (about 3.8 cm per month), growth was fitted by inspection (Mather and Schuck 1960). and it was evident that their average

11 .0 May and June and from Nova Scotia 80 ..•.....- in July to September. He estimated a /0 7.5% per month increase in weight • ~+•• of these fish during their sojourn in 70 ~e: Nova Scotia waters. ::r.:" Butler (1974) supported Rivas' to.;; A.o- ••·~ 60 i'· . findings for the northern fish. He ex- ~ I4.j amined giants taken near Prince Ed- ...• ~~o. ward Island between July and Octo- +~2A 50 YEAR CLASSES IjJ.tto+- ~ ber 1974. By calculating weekly 01"'& . 1949 mean weights during this period But- ~ 40 0 1950 ler showed an approximate weight ;. • 1951 + 1952 gain of70 kg in 12 weeks. He refined 30 /),. 1953 these data and calculated a 30 kg per month gain between August 19 and October 4, 1974, or about 10% per IX XI III V VII IX XI III V VII IX month. MONTHS The present authors have calculated length-weight relationships for Figure 9. Curve of linear growth of young bluefin tuna (caught off the Atlantic various monthly periods for bluefin coast of Morocco) up to the beginning of their third winter (Fumestin and tuna taken during the fishing seasons Dardignac 1962). in two parts of the western North

growth rate during the remainder of considerable part of the coastal habi~ Fork length I MOIl Girth the year must have been much slower tat of the species. (about 0.8 cm per month)(Figure 8). ]n the North Sea area Bahr 1.4 Furnestin and· Dardignac (1962) (1952), Tiews (]957) and Luhmamn were able to collect material of ages (1959) observed an increase in weight 0-2 throughout most of the year along in relation to length during the fish- the Atlantic coast of Morocco. Their ing season of August to October. 1.2 data for winter sizes fitted very well Tiews (] 957) showed that tunas of with corresponding data for January 215-240 cm increased their weight obtained by extrapolation from during their 2-3 month stay in the Mather and Schuck's (1960) results. North Sea by about 11.0 kg in 1954 o '-; 1.0 Fork lengthl Tolal Weight ]t also showed that growth virtually and 17.4 kg in 1955. This worked a: ceased from January to March at age out to about 34% to 54% of their 0, and at the end of November, when yearly weight increase. Luhmamn the fish were about 63 cm long, at (1959) pointed out that variations in , 0.8 , age I. Data for age 2 were incom- the length-weight relationship in dif- ,, plete, but suggested that in autumn ferentyears might be directly associ- MoIIi " ~ they had practically reached their ated with variations in feeding con~ -....••..... winter length of about 85 cm ditions. ..•...... •.. --..• 0.6 (Figure 9). Rodriguez- Roda (1964) ob~ served that during the spawning sea- 4. Seasonal Changes in the o I I I I son, from May to August along the July AUII Slpl Oc I Noy Length-Weight Relationship of south Atlantic coast of Spain, mature Large Rluefin Tuna fish lost about 14.73% of their weight Extensive seasonal changes in between the pre- and post-spawning Figure 10. Seasonal ratios offork length the length-weight ratio of large blue- state. to maximum girth and fork length to fin tuna have been found by many In the western Atlantic, Rivas total weight by sex for all areas investigators working in different ar- (1955) studied records of the weights combined. (Caddy et a!. 1976) eas which collectively represent a of giant tuna from the Bahamas in

12 Table 6. Factors derived from the length-weight fonnula for Area I (north of the sexes, the males must be consid- latitude 35°N and west of longitude 50°W) and Area 2 (Straits of Florida and erably heavier posteriorly than the adjacent waters). females.

Season A B Length (em) 6. Ultimate Length The asymptotic or ultimate Area 1: length (La» of Atlantic bluefin tuna June - 4.2571 2.7871 50-260 has been estimated from some growth studies. Rodriguez-Roda (1964a, July - 4.3893 2.8497 50-260 1971) presented an La>of 355.8 em, Aug. - 4.5540 2.9290 35-270 derived from his age determinations 2.9391 35-270 Sept. - 4;5651 for bluefin tuna collected off the act. . - 4.7330 3.0192 35-270 southern Atlantic coast of Spain. July-Sept. - 4.4989 2.9044 35-270 Caddy et al. (1976) derived an La>of Aug.-act. - 4:0333 2.8606 35-270 447.88 em from the age-size data of Mather et al. (1974), an average of Area 2 several previous works, and an La>of 286.64 em for males and 277.315 em May-June - 4.8070 2.9044 185-260 for females from their own determinations for fish taken in Canadian waters. The longest bluefin tuna entered for record consideration by the International Game Fish Association Atlantic. Area I comprised waters come to our attention. Few of the as of December 1976, weighed 540 north of latitude 35°N and west of publications on the growth of the spe- kg and was 312 cm long (FL) (the 0 longitude 50 W. Area 2 included the cies present data in terms of sex of method of length measurement used Straits of Florida and adjacent wa- fish. Hamre (1960) found no signifi- was not specified) (E. K. Harry, per- ters. Factors derived from the fol- cant difference in growth between sonal communication). Larger blue- lowing length-weight formula are males and females. fin tuna have been reported in the shown in Table 6: Tabulations of age determina- literature. For example, Hamre et al. W=A +B Log L tions by sex offish (Rodriguez-Roda (1971) reported an individual in the 1964) indicate that males attain larger where: 310-315 cm range measured at the sizes than females. The data suggest, Istanbul (Turkey) fish market in Janu- W is the live (whole) weight of the however, that this difference is due ary 1967. Unfortunately, the weights fish (kg), and to greater longevity for males, rather of many large bluefin are reported than a difference in growth rates. L is the fork length (em) without any information on their Rivas (1976) reported that, on the length. Sara (1969) mentioned blue- average, the males in samples oflarge Unpublished data collected by fin tuna of 625 and 685 kg taken in bluefin taken off the Bahamas and in Schuck and Mather showed that al- traps off Sardinia in 1969 and the Gulf of Mexico in various years though there was a marked increase Scaccini et a!. (1975) cited fish weigh- were 4 % longer and 13 % heavier in the length-weight ratio of large ing up to 600 kg taken in the than the females. bluefin from June through October, Favignana trap off western Sicily in As noted in part I ofthis subsec- the length-weight ratio of individu- June 1974. tion, Caddy et al. (1976) found con- als less than 100 em long did not sistent differences in length for age 7. Discussion change noticeably from month to between large male and female blue- There has been good agreement month during the summer. fin caught in Canadian waters in 1975 on the size for age of Atlantic bluefin 5. Differential Growth of Males (Figure 5). These authors also found tuna for ages I-II (Table 4). There and Females differences in the length-weight rela- is less confidence in detenninations Although some authors noted tionship between males and females for older ages. Caddy et al. (1976) that male bluefin tuna attain larger in the period July-November (Fig- extended estimated age determina- sizes than females, only two studies, ure 10). Males are heavier than fe- tions to 25 years, and also provided those of Caddy et al. (1976) and But- males of the same length. Since, as separate von Bertalanffy growth ler et al. (1977), showing a consis- this figure shows, there is very little curves for males and females (Fig- tent difference in growth rate have difference in maximum girth between ure 5). These authors note that ear-

13 Iier age determinations had ascribed 227-272 kg, 272-317 kg and 318- It is also important that the lin- fish smaller than 245 cm to age group 362 kg), their ages were 2-3 years ear growth rate of the early stages of 8, whereas their own determinations less than those of Mather and Schuck bluefin tuna be determined for the indicated that 245 cm was roughly (1960), 3-4 years less than those of various spawning areas. This infor- equivalent to ages 14-15 for males Butler (1975), and 4-5 years less than mation is needed in terms of length, and age 18 for females. They also those of Caddy et al. (1976). They rather than weight, to permit better asserted that apparent underestimates attributed these discrepancies to the estimates of spawning dates and lo- of the ages of fish more than 240 cm interpretation of growth marks on oto- calities from the collection data for long had resulted in estimates of Loo liths and vertebrae, mainly in fish these stages of the bluefin tuna. based primarily on data from fish more than 10 years old. In these older Seasonal variations in the growth less than 12 years old, which were in fish, they often found double or mul- rates of blue fin tuna up to 4 years old excess of any sizes recently recorded tiple markings which, they believed, are reasonably well known (Mather for Atlantic bluefin tuna. If their re- represented subdivisions of a single and Schuck 1960, Furnestin and sults should be validated, consider- year's growth. They assumed that Dardignac 1962), but the data now able revisions of recent estimates of other workers had counted each such available should permit extension of the age composition of the Atlantic mark as representing a year's growth, this knowledge to older ages. The bluefin tuna stocks (Sakagawa and resulting in a tendency to overesti- possibility that the growth rate of the Coan 1974) would be required. mate ages. Atlantic bluefin tuna has increased Berry et al. (1977) questioned It is most important that the ac- as the size of the stock has decreased previous age determinations for large tual age composition of the "relict" should also be investigated. This pos- Atlantic bluefin tuna. In the size population (as described by Caddy et sibility is suggested by the remarkable ranges for which they provided aver- al. 1976) of giant Atlantic bluefin number of extremely large bluefin age ages (136-181 kg, 181-226 kg, tuna be determined. caught since 1970 (see Section IV).

14 IV. DISTRIBUTION AND FISHERIES

75' A. GENERAL DI&TRIBUTION

The bluefm tuna has been reported at one season or another over an extraordinarily large area of the Atlantic and the adjacent seas, and in a wide variety of water types (Fig- ures 11 and 12). In recent years it has ranged off the Atlantic coasts of Europe and Africa, from the North Cape, inside the Arctic Circle, to the Cape of Good Hope, and off the American coasts from Newfoundland to 400S latitude, and also in most of the intervening oceanic areas. It also has been present in most of the adjacent seas, the North, Mediterranean, Black and Caribbean Seas, and the Gulf of Mexico. The distribution of the bluefm tuna has varied greatly with the sea- C' sons and with the size of fish (Fig- ure 13). Seasonal variations are in- L~TS OF RANG-E--- AREAS OF OCEANIC fluenced by the requirements of LONG LINE CATCHES MAJOR LONGLINE spawning and feeding, and by water CATCHES COASTAL LINE temperature. Tiews (1963) concluded FISHERIES that distribution was limited by the 12°C (surface temp erature) isotherm. Distributional changes with size of .fish are probably related to the change from a planktonic diet to one of small 40" fishes during its first few months of Figure 11. Bluefin distribution Oongline catches off southwestern Africa probably life, to its first spawning at 3 to 5 consisted mainly of southern bluefm, Thunnus maccoyii). years of age, or, possibly, to the full development of its swim bladder at ages 8 to 10 years (Sella 1929b, Sara 1973). Year-to-year changes in distributional and migratory patterns are frequent. Variations in environmental conditions and the availability offood are regarded as the major causes of these changes.

B. DEVELOPMENT OF THE MAJOR FISHERIES Large scale fisheries for bluefin tuna have existed in the Mediter- ranean and its approaches for centuries, but those in the remainder of the Atlantic are of more recent origin. Several methods and gears have been used. The oldest large scale 45· 30° method is the tuna trap, which has been used through most of the Chris- Figure 12. Bluefin regions of capture by seine, live bait, and trap. tian era and perhaps. much earlier

IS NORWAY NEWFOUNDLAND f N of &3- ••• 15. [ to. '960-'970 19!MHHI

& o 16. l PA'INCE EDWARD I$LA"'D to. .969-197'

SCOTIA to'~·lNOVA'941;;- '95&, '969 s. I o NOItW.t,V ':: 15. r loiIAINE ana I PSWI CH 8AY (S of 11.5- N) ~ 10 -1947-19!:l' 1962-'970 ~..• ~ 5

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BAHAMAS '5. f FRANCE 10. 1939,t947 -'954,1966 19M- (MEDITERRANEAN. '969 5.

00 tOO 150 zoo LENliTH (filff I

(pavesi 1889, Parona 1919). These were set near the coasts and the more important ones depended on the spawning migrations of the bluefin in the Medi- terranean and its approaches. An eastward or "arrival" run of prespawming fish occurs in May and June in many localities, and a westward or "return" run of spent fish occurs in July and August in some of these, and in some other locations. Most of these tuna traps were designed to catch fish coming from one direction only, but a few were reversed between the seasons and fished both runs. Less elaborate traps have taken bluefin tuna in many localities during other 100 ISO tOO :UO '00 seasons .. L£N6TN(cm) Handline and harpoon fisheries have existed in many areas, in some cases for centuries, taking relatively small catches. Specialized gears, such as the Figure 13. Lengths of bluefin tuna by region ("+" on graph "thonaille" (a drifting entangling net) and "seinche" means less than 0.5%).

16 (a complex multi-boat seine) of south- men in 1950.Catchespeaked at 2,400 Cape Cod, Massachusetts, in 1962 ern France (Doumenge 1953) and the tons in 1952 and amounted to 1,800 (Wilson 1965). The catch of small "cianciolo" (a modified seine) of Sic- tons in 1959 (Tiews 1975). Thus two bluefin rose to 5,600 tons in 1964, ily (de Gaetani 1948), have been used virtually new fisheries began to take along with an almost equal quantity locally, and generally on a small great quantities of large bluefin in of skipjack tuna, Katsuwonus pelamis scale. (Linnaeus 1758). The largest fleet in the northeastern Atlantic at the same Since World War II, great the history of the fishery, 21 vessels, changes have occurred in the Atlan- time that the only important fishery including some of the world's larg- tic and Mediterranean bluefm fisher- in the area for small bluefin, in the est, was responsible for this catch. ies through the introduction of three Bay of Biscay, greatly increased its Subsequent annual catches have var- much more productive methods: live- catches by adopting the live bait ied considerably between a low of bait, pelagic longline,andpurse seine. method. The German handline 600 tons in 1966 and a high of 3,600 In addition some fisheries using the catches declined to 200 tons by 1962 tons in 1971. older methods were initiated or ex- and the fishery was abandoned after The Japanese 10nglinefisheryen- panded. the 1963 and 1964 seasons produced tered the Atlantic in 1956, and subse- The traditional trolling fishery only one fish each. quent expansion was rapid (Shiohama for small bluefin and albacore, Purse seining for bluefin tuna et a!. 1965). By 1962, most of the ocean between latitudes 25°N and Thunnus alalunga (Bonnaterre 1788), also became widespread in the 25°S was being fished by Japanese in the Bay of Biscay was largely con- Mediterranean. Yugoslavian fisher- verted to the much more productive longliners. In 1969, the fishery had men evidently introduced the method expanded so that most of the waters live-bait method between 1947 and in the Adriatic in 1929 (Tilic 1954). between 400N and 400S were being 1949 (Navaz 1950a, 1950b; de la Joined later by Italian fishermen, they fished (Wise and Davis 1973). The Tourrasse 1951). The French catches have seined small bluefin extensively catches of bluefin tuna were small increaSed from 600 tons in 1948 to in the Adriatic (Scaccini and Bian- (less than 7,000 fishper year) in 1956- from 1,900 to 3,500 tons per year in calana 1959, Morovic 1961). Sein- 1961, but increased to 53,000 to 1950-1959. In 1960-1970, however, ing of small bluefin has also been 67,000 fish per year in 1962-1965. they declined to between 400 'and carried out by Italian fishermen in They then declined to less than 1,000 1,600 tons, exceeding 1,000tons only the Tyrrhenian and Ligurian Seas, per year in 1969 and 1970. The 1971 catch was 8,000 fish, however, and once (Aloncle 1972). The 1970 and but with less modem equipment. Very 1971 catches were also below 1,000 the catch had risen to about 46,000 small bluefin are seined by sardine fish by 1974 (Fisheries Agency of tons (Bard et a!. 1972). The live-bait boats with "cianciolo." In 1972 Ital- Japan 1976). This was due mainly to method has also come into use in the ian fishermen began to take consid- the entry of the fishery into areas fishery for small bluefin off the At- erable quantities of giant spawning which had formerlybeen unexploited, lantic coast of Morocco (Lamboeuf bluefin in the Tyrrhenian Sea and the or cxploited only by inshore gears - 1972). Sicilian channel with large modem the oceanic eastern Atlantic, the Bay The highly effective purse seine purse seiners (paini 1975). of Biscay, the Ibero-Moroccan Gulf, method has also been widely intro- The seining of bluefin tuna off and the Mediterranean. duced in the Atlantic and the Medi- the Mediterranean coast of France Japanese longliners entered the terranean. The first important step was authorized in 1960 and devel- bluefin tuna fishery in the Bay of Biscay in 1974, reportedly affecting was the development of a seine fish- oped rapidly (di Meglio 1962). Sar- the operations of the local Spanish ery for mediwn sized and giant blue- dine boats occasionally seine bluefin fin off Norway in the late I940s. The fleet (Cort and Cendrero 1975). Their tuna, including extremely small ones, catches in the area in that year to- annual Norwegian bluefin catches off the Mediterranean coasts of Mo- talled about 11,215 fish (Fisheries increased from a few hundred tons in rocco and Spain (Rodriguez-Roda Agency of Japan 1976). the middle 1940s to about 10,000 1964a, 1964b). Small bluefin tuna Japanese 10ngliners entered the tons in the middle 1950s (Hamre are also seined off the Atlantic coast Mediterranean in 1972. Their total 1971). Catches declined greatly after of Morocco (Aloncle 1964, catch that year included 112 tons of 1962, varying from 200 to 2,500 tons Lamboeuf 1972) by sardine vessels, Atlantic bluefin tuna. This increased per year in 1963-1971, collapsing to sometimes with the assistance of to 246 tons in 1973 and 2,195 tons in about 100 tons in 1972 and 1973, chumming by live-bait boats. 1974 (Miyake and Manning 1975). Much of this catch was taken in the and rising to 800 tons in 1974 Purse seine fishing for bluefin (Miyake and Tibbo 1972, Miyake and tuna, practiced in Cape Cod Bay by vicinity of Sicily in June and July, Manning 1975). only one or two very small vessels in during the spawning season (Shingu et a1. 1975, Shingu and Hisada 1976, A handline fisheryfor giant blue- 1958-1961 (Squire 1959), expanded Fisheries Agency of Japan 1975, fin tuna in the North Sea was origi- to an oceanic fishery ranging from Cape Hatteras, North Carolina, to 1976). The concentration oflonglines nated by German and Danish fisher- around Sicily reportedly made it al-

17 most impossible for the Italian sein- as 1971. Apparently, however, cen- 2. Western Atlantic ers to set their nets (Paini 1975). In tral Mediterranean (Italian, Tunisian, The major fisheries for bluefin 1975 the Japanese government pro- and Libyan) trap fisheries, havc re- tuna on the western Atlantic conti- hibited their longliners from fishing cently undergone a collapse similar nental shelf are concentrated between in the Mediterranean as part of its to that experienced by those in the Cape Hatteras, North Carolina, and compliance with the ICCA T regula- eastern Atlantic. Catches were fairly Newfoundland, Canada(Figure 14). tions (Kume 1976). good through 1969, but in 1972 and The small fish have been predomi- Numerous longline vessels of 1973 traps which had formerly pro- nant in the area between Cape South Korea, Nationalist China, duced thousands of fish per year Hatteras and Cape Cod, Massachu- Cuba, Venezuela, and the Soviet yielded only a very few hundred. setts, but medium sized and giant Union have also caught bluefin tuna, Only a handful of the once numerous fish have also occurr.ed .there in num- Italian traps survive. This decline has along with other species, in the At- bers on occasion. Giant fish have been been offset recently by the entry of lantic in recent years (Miyake and predominant in the region between the Japanese longline fishery into the Cape Cod and Newfoundland in re- Tibbo 1972). area and the development of the Ital- cent years. Until 1966, medium sized Offshore big game fishing for ian purse seine fishery for giant blue- bluefin were often abundant between bluefin tuna and other large oceanic fin in the central Mediterranean. It Cape Cod and Nova Scotia. In some fishes (chiefly billfishes) became should be noted that both of these years during the 1950s, small bluefin popular in parts of the northw.estern fisheries also use spawning concen- were the most numerous size group Atlantic during the 1930s (Farrmgton trations. in northern Massachusetts waters, but 1939) and expanded to a highly de- Another notable trend in nearly we have never heard of their occur- veloped pursuit after World War. II all of the Atlantic and Mediterranean rence in significant numbers off (Farrington 1949). Centers of tn- fisheries for large bluefin for which Canada. tensive sport fishing for bluefin tuna data are available has been the virtu- The gears used for bluefin tuna have been off the northwestern Ba- ally complete absence of medium in this area include harpoons, hand hamas in spring, and along the United sized (32-122 kg, ages approximately lines, traps, rods and reels, and purse States coast from Virginia to Maine 5-8) and a marked scarcity of small semes. and in Canadian waters off south- giant (123 -200 kg, ages approxi- Some giant bluefin have also western Nova Scotia, eastern New- mately 9-11) bluefin from the catches. been taken by sport gear off the north- foundland, and in the Gulf of St. This trend has been reversed in the western Bahamas and by small-scale Lawrence in summer and early fall. central Mediterranean fisheries in commercial fisheries off some Cu- Thousands of private and charter 1975 (Miyake 1976). ban ports. Captures of bluefin tuna boats have participated in this fish- In the following section, we will elsewhere in western Atlantic coastal ery, with as many as a thousand an- discuss the distribution of Atlantic waters have been insignificant. glers in two hundred boats entering a bluefin tuna and the fisheries for it in single tournament. Sport fishing for detail. a. Newfoundland to Cape Cod bluefm tuna has also been popular in eastern Atlantic and Mediterranean i. Newfoundland waters. Centers have been the C. DISTRIBUTION AND There has been little commercial fishing for bluefin tuna off the Oresund off Denmark, the North Sea FISHERIES BY AREAS off England, the Canary Islands, the Canadian island of Newfoundland (Figure 15), but good sport fishing Bay of Biscay off northern Spa~n, the 1. Introduction for the species was enjoyed there from Italian Riviera, and the MedIterra- In this section we will discuss 1961 through 1972. nean coasts of France and Spain. Re- the following information, by area: This fishery was initiated at Con- cent low availability of fish has re- I) Times and locations of occur- ception Bay in 1956, and was well duced interest in sport fishing in sev- rences of blue fin tuna, and thcir varia- developed there by 1961. Another eral of these areas. tions with size of fish. productive ground, Notre Dame Bay, The northeastern Atlantic fish- 2) Fisheries and fishing mcth- was opened in 1967, with most of thc eries for large and medium sized blue- ods. boats based at Lewisporte. The fish- fin tuna began a decline in 1963 3) The volume and size compo- ing usually extended from mid-July which reduced several of them to ex- sition of the catches, and their trends. to mid-October. From 1961 through tinction by 1973. Bluefin tuna pro- The size composition by years 1972, catches of up to 635 fish were duction in the Japanese oceanic of samples of the catches of most of taken in Newfoundland waters each longline fishery peaked rapidly in the major fisheries is illustrated by season. Many of these fish were 1962-1965 but declined to a low level histograms. The tables from which tagged and released. The catch has by 1967. most of these histograms were plot- declined drastically since 1972, with The reported total catches of the ted have becn reproduced, with the less than 100 fish being taken each Mediterranean fisheries, on the other sources of the data, in lCCAT Data season. Nearly all of the catch con- hand, appeared to be maintaining Rccord, Vol. 3, Madrid, 1974. themselves satisfactorily as recently sisted of giants, and their modal

18 I of fish to reduce the catch in 1975 1 1 (Caddy and Burnett 1975). I I The success of the Prince Ed- • CITIES I I ward Island fishery and exploratory I I efforts by visiting United States an- I I I glers resulted in the extension of the I sport fishery in 1973 to Chaleur and i" Gaspe Bays, New Brunswick. This fishery increased rapidly and took 93 fish with an average weight of 801 Ibs (363 kg) in 1974 and 148 fish with an average weight of 858 Ibs (389 kg) in 1975 (D. A. MacLean, personal communication). Potential world record rod and reel bluefin weighing 1,190 Ibs (540 kg) and 1,200 Ibs (544 kg) were taken in Chaleur Bay in 1976 (E. K. Harry, personal communication). The continuing increase in the sizes of the bluefin taken in the Gulf of St. Lawrence, and the lack of recruitment to the fishery, are vividly illustrated by the weight composition of the 1974-1976 catches (Fig- ure 17). iii. Nova Scotia Bluefin tuna have long been taken by traps and harpoons in Nova 800 Scotian waters, but the only histori- Figure 14. Geographical references in the northwestern Atlantic. cal size data are from the sport fishery. The sport fishery was first developed in 1935 at Wedgeport south of Yarmouth) (Figure 19) where it length increased from about 220 cm in 1973 (Anonymous 1974). Almost was very successful for many years. in 1961 to about 240 cm in 1971 all of the fish taken have been giants In the mid 1950s, however, the fish- (Figure 16). Their mean weight rose (Figure 18). The average weight of ing there deteriorated, and Nova likewise, from 220 kg in 1961 to 314 the fish caught has remained consis- Scotian fishing has been centered at kg in 1975 (Caddy and Butler 1976). tently over 300 kg, and rose sharply Cape St. Mary (north of Yarmouth) to 382 kg in 1975 (Caddy and Butler since then. Our data extend from 1946 ii. Gulf of St. Lawrence 1976). With increasing fishing ef- through 1955, and also include 1959. In recent years, more extremely fort, the total catches rose to a peak The size composition of the catches large bluefin tuna have been taken of 1,048 fish in 1974, but declined varied considerably over these years on rod and reel in the Gulf of St. sharply to 343 fish in 1975 (D. A. (Figure 20). Giants dominated the Lawrence (Figure 17) than in any MacLean, personal communication). catch in 1946, but medium sized fish other area. No less than 36 out of 487 In 1972, the Canadian Minister of became more important in succeed- tuna caught in the Gulf in 1975 ex- Fisheries restricted bluefin tuna fishing years, ';.dominating the catch in ceeded 1,000 Ibs (454 kg) in weight ing in the Gulf of St. Lawrence to rod 1949 and providing over 40 percent (D. A. MacLean, personal communi- and reel, using lines of not over 130 of those in 1948 and 1950. The year cation). Ib (59 kg) test (Anonymous 1974). class of 1942 was dominant in 1948, The sport fishery was initiated at In 1975 the Minister restricted the and that of 1943 was dominant in Prince Edward Island in 1966. The fishing to 10 week seasons and the 1949-1950, and important in 1951 season originally extended from late catch to two fish per boat per day, (Mather and Schuck 1960). Giants July into October, but the high prices using rod and reel only. In addition, again dominated through 1955, ex- offered for large bluefin tuna caught licenses were limited to boats which cepting an important showing of me- in the late season resulted in its ex- had fished in 1974. These n.:stric- diums (year class of 1949) in 1954. tension into November, and also in tions, which were part of Canada's In 1959 mediums were again domi- an increase in the number of boats compliance with the ICCA T regula- nant (year classes of 1952 and 1953). fishing from 30 in 1972 to about 72 tions, combined with poor abundance The few catches in recent years have

19 (1977) has provided details on its recent trends and developments, and ~ CITIE 5 its status in 1976. Additional data are @ GEOGRAPHICAL available in Butler (1975), Caddy and RE FE RENCES Butler (1976) and statistics of Envi- 1 BONNE BAY ronment Canada (D. A. MacLean, 2 CONCEPTION BAY personal communication). :5 TRINITY BAY Young (1974) stated that land- 4 FO GO ISLAND ing statistics for the fishery have been !l NOTRE DAME BAY recorded since 1918, but the fishery 6 HAMILTON INLET predated the establishment of statistical systems. The recorded annual catches of large fish have been in the order of 400, but have ranged as high as 1,500. There was also a second later run of much smaller fish, in the 20-70 kg range. None of the small fish have been seen in recent years, and the 'average weight of larger fish increased considerably, reaching 295 kg in 1974 The weight composition of the 1973- 1975 catches (Figure 21) shows a considerable increase in sizes of fish taken each year, and only fragmentary recruitment of younger fish to the fishery. The estimated numbers of fish caught in the period 1964-1975 varied between 104 (in 1972) and 865 (in 1974) (Butler 1977). In June 1974 an additional 150 tuna caught in the traps were tagged and released. Ton- nages in the years 1971-1 975 ranged from 23.6 mt in 1972 to 256 mt in ~ 1974 (Caddy and Butler 1976, Butler /.j 1977, D. A. MacLean, personal com- CAPE BRETO"l ISLAND :\.' . munication). The average weight of the fish increased from about 227 kg in 1971-1973 to 295 kg in 1974 and 319kgin 1975. Figure 15. Geographical references off Newfoundland and Labrador. Butler (I977) described a most interesting development in this fishery - the holding of giant bluefin in impoundments, and fattening them, been of very large giants. Their aver- Tuna Cup matches since their incep- to secure optimal prices. Japanese age weight has also increased in re- tion in the 1937 season. As docu- interests offer very high prices for cent years, reaching 761 Ibs (345 kg) mented by Farrington (1974), these fresh giant tuna in the fat condition in 1974 and 8241bs (394 kg) in 1975 competitions were held at Wedgeport which they attain in late summer arid (D. A. MacLean, personal communi- through 1957, except for one at fall through heavy feeding. The prices cation). The fishing off southwestern Liverpool and an interruption caused offered for the typically lean fish Nova Scotia usually extended fi'om by World War II. Subsequent matches taken in the early season are much early July to late September or Octo- were held at Cape SL Mary in 1958 lower. Butler stated that the average ber. The giants have been most abun- and from 1965 through 1975. price per pound offered to Canadian dant in August and September, but Bluefin tuna have been an im- fishermen for giant bluefinin 1976 the medium fish, which arrived and portant incidcntal catch in the mack- varied from $0.20 in July~August to departed later than the giants, have erel trap fishery at St. Margaret's Bay $1.40 in October. The St. Margaret's been most abundant in September and (near Halifax) Nova Scotia (Figure Bay traps normally take most of their October. Nova Scotia has been the 19). Young (1974) briefly reviewed catch of giant tuna in the early sea- locale of the prestigious International the history of the fishery, and Butler son, when the price is low. In an

20 30

20 t960 ~966

() :so

20 t96t t967

0 SO

20 t968

10 ~" ~ ~ 0 fit 30 ~ I 20 1963 1969

0 ~o

20 t964 t970

0 30

20 t9IS 1911 to

0 • ,~ I I I I \ I ..• \ 1 I I I 50 tOO 1~0 ZOO 250 300 50 100 150 200 ~OO LENGrH(cml LENGTH (em)

Figure 16. Lengths of blue fin tuna captured ofl'Newfoundland (1960-1971) ("+" on graph means less than 0.5%).

21 80 1976 methods in the New England area (Figure 22) (Bigelow and Schroeder 60 ~- Caraquel 1953, Wilson 1965). The traps, which c:J. Prince Edward Island were formerly numerous in Cape Cod 40 Bay, took considerable quantities of these tuna in years of abundance, but the fishery there was t~rrriinated in 20 1975. Operators of various types of commercial fishing craft, such as lob- 0 ster boats and small trawlers, occa- so: sionally harpooned b1uefin Of. caught ~ 40 1915 them with handlines. This activity was usually incidental to their nor~ "0 mal pursuits or undertaken tempo- 20 ~ rarily during periods when tuna were ...•41 e readily available and commanded a ::> 0 Z reasonable price. Sport fishing for bluefin tuna 80 1974.. . developed in the area in the 1930s (Farrington 1939) and increased in SO popularity after World War II (Farrington 1949). Pre-war activitY centered in Ipswich Bay, Massachu- 40 setts, and Casco Bay, Maine. After the war the popularity of sport tuna 20 fishing spread into Massachusetts and Cape Cod Bays as well. Some of the

0 most successful giant tuna. tourn~. ,1 100 200 ~OO 400 500 ments ever held have taken place· in WEigh!. (10 kg groupings)

Figure 17. Weights of giant bluefin tuna caught by rod and reel in the Gulf of St Lawrence (1974-1976).

30 effort to capitalize oil the high late season prices, two impoundment nets 20 1969 were constructed in the Bay in 1975. Each impoundment measured about 10 100 m x 50 m, and was in water about 20 m deep. Fifty bluefin were trans- 0 ferred from neighboring traps to the lo.J 30 pounds. They were fed on trash fish ~ and held for a period of two or three ~ 20 1970 months. Then they were killed in ~ 10 small batches, to avoid depressing the ~ price, and sold on the Japanese mar- ~ ket. The experiment was so success- 0 ful that nine impoundments were con- 30 structed in 1976, and about 300 blue- 1971 fin were held and fattened. 20 Butler (1977) showed the loca- 10 tions of the traps and impoundments in St. Margaret's Bay and discussed 0 past and proposed research activities 50 100 150 200 250 300 in this unique situation. LENGTH(cm) iv. Cape Cod to Maine Bluefin tuna have occurred in Figure 18. Lengths for bluefin tuna captured off Prince Edward Islan~ (1969- many sizes and been fished by many 1971).

22 66° 62° 60° ginning of this period of increased GIILF OF sr LAWRENCE effort and estimated catches of 3,000 and 3,500 fish in 1972 and 1973 respectively .. , 48° In 1974, the Commonwealth of Massachusetts regulated the fishery for large b1uefm in its waters and 47° collected data on the landings. The National Marine Fisheries Service also initiated a data collection program for the fishery. The resulting data are shown in Table 7 (F. H. 46° Berry, personal communication). The data for the rod and reel and harpoon

~ CITIES and handline catches were estimated ..

@GEOG"APHICAL REfERENCES Since 1975 quotas have been im- t CAPE ST. aAARV posed on these fisheries to control 2 YARMOUTH the number of large fish taken each 3 SHELBURNE HARBOR 4 CAPE R05EWAY year and to prevent the capture of the 5 JORDAN BAY 44° surviving small fish (National Ma- , LIVERPOOL 1 MAHONE BAY rine Fisheries Service 1975, 1976). B ST. MARGARETS SAY Under the 1975 quotas, the recorded o I' aD 7B lOG l I • I • 9 ST. ANNE BAY NAUTICAL MillS catch by hand gears (harpoon, 10 NORTHUM!lfftLAND STRAI T 43" handline and rod and reel) was 2,277 fish weighing 693.5 tons, with an average weight of 305 kg. The recorded seine catch. was 1,017 fish Figure 19. Geographical references of Nova Scotia. weighing 267.2 tons with an average weight of263 kg (A10ncle et a1. 1976, ICCAT 1976). The time of the best fishing in these waters in the years 1972-1976. medium fish have been found in the Cape Cod Bay has varied consider- Large bluefin were remarkably avail- Gulf of Maine since 1964. For sev- ably - partly according to the sizes able in those years, and their average eral years thereafter, seining in the of the fish which entered the area. size was increasing steadily. area was limited to occasional trips !he giant fish usually arrived early, The purse seine fishery for b1ue- by one or two vessels after the sea- m June or early July, and stayed into fin tuna ofIthe east coast of the United son for small bluefin southwest of September or October. Peak fishing States originated in Cape Cod Bay Cape Cod had terminated. This situ- was usually in August or September. and its vicinity (Wilson 1965). After ation was altered by the high prices Medium sized fish have usually initial experiments in 1951 and 1954, offered from 1972 on by Japanese arrived later, and also stayed in the a continuing purse seine fishery be- interests for the fat bluefin which Bay later than the others, being abim- gan in 1958 with a single small ves- were caught late in the season. A dant in August-October. Exceptions sel operating out of Provincetown, local seiner, who spccialized in catch- occurred when the smaller (age 5) Massachusetts. Very high catch rates ing giant fish, had fished in the Bay individuals of this group accompa- were obtained from the schools of for the Japanese market toward the nied early summer runs of small (age medium sized b1uefin which were end of each season since 1972. In 2-4) bluefin. Small b1uefin were un- then abundant in the Bay (Sakagawa 1976 a second vessel joined the fish- predictable. Some strong runs peaked 1975). In 1962 the carrying capacity ery. iIi.early sUinmer, asin 1951 and 1953, of the fleet was greatly increased by The prices offered for large blue- but others have occurred in late sum- the purchase of additional vessels by fin tuna also caused a dramatic inmer, as in 1950. local fishermen and visits by larger crease in fishing effort by the har- As noted above, fishing tech- ones from other areas, and the fish- poon, handline and sport fisheries. niques in the area have changed over ing area was expanded southwest- The "sport" fishery, differed only in the years. Also, catch records have ward to include the New York Bight the gear used,' since virtually all of not been kept in a consistent manner. and more southerly areas. The large the anglers were fishing for the mar- We do have sporadic records of the fleets which entered the fishery in ket. Boats of all types and sizes, from sizes of fish landed for Ipswich Bay 1963 and 1964 made considerable small outboard motor boats to large and the Maine coast for 1947 -19 51 portions of their catches of small and trawlers andparty,fishirtg boats, par- (Figure 23) and more comprehen- medium b1uefin in Cape Cod Bay ticipated. sive ones for Cape Cod Bay and vi- and vicinity, especially toward the Mather and Mason attempted to cinity (including Ipswich Bay from end of the season. Very few small or gather catch records during the be-

23 '0

20 t9~2

0 &>

20 t947

0 Iq 30 ~ ! 20 t954 10 l.... ~ lit 0 30

20 1919 19~15

0 50

20 1950 '959

0 110 1QO 150 200 300 30 LENGTH (em")

20 1951 1960 on) for 1947-1975 (Figure 24). 10 As the latter figure shows, the size composition of the samples has var- 0 50 100 150 200 250 :500 ied drastically over the years. In 1947, LENGTH (cmJ giants were dominant, with a fair proportion of mediums in Cape Cod Bay. Figure 20. Lengths for bluefin tuna captured off Nova Scotia (1946-1959) ("+" The mediums, mainly the year class on graph means less than 0.5%). of 1943, which was also outstanding in the Nova Scotia catches of 1949- 1950 (Mather and Schuck 1960), be- 30 came dominant in Cape Cod Bay in 70 197:5 1948 and 1949. They would have to been dominant in 1950 also but for o an apparently unprecedented influx ••• 30 of small blucfin. This 1948 year class ~ remained dominant through 1957. :t; 20 1974 ~ The mediums became dominant again ~ ,e in 1958-1960, mainly because of the ill! o progression of the velY strong year class of 1952 through this size category. This year class was also prominent in the 1959 Nova Scotia catches. In 1961, small, medium, and giant

50 tOO 150 200 250 300 350 <400 450 bluefin were all represented, but an- WEIGHTflrg) other strong year class (1957) had Figure 21. Weights of bluefin tuna captured from St. Margaret's Bay ("+" on become dominant.' The progression graph means less than 0.5%). of this class made the medium group

24 ally, but very few of these are now in 72° operation. The bluefin tuna has been one of the most abundant and popu- ~ CITIES @ GEOGRAPHIC REFERENCES lar hig gamc species supporting the I CAPE COO BAY offshore sport fishery of this area, Z MASSACHUSETTS BAY 3 IPSWICH BAY particularly in its northeastern part. 45° " BOONE ISLAND ~ OGUNQUIT Since 1961 it has also been the object 6 BOOTHBAY HARBOR 7 PEMAQUID POINT of a seasonal purse seine fishery B MUSCONGUS BAY 9 MOUNT DESERT t which also takes skipjack tuna in BAKERS L 10 ORAND MANAN I. some years. Bluefin usually arrived 11 PASSAMAQUODDY BAY lZ ST. JOHN in the area in late June or early July 13 DIGBY and departed in the early fall, but they sometimes departed as late as November. The size composition data available to usfor this area (Figure 24) are mainly from the sport fishery for years before 1961, and from the purse seine fishery for later years. As indicated by these histograms, 42° the sport catches have consisted almost entirely of small bluefin, mostly of ages 1-3. Sport fishing for these bluefin has been very successful in 41° some years off New York· Harbor (Westman and Neville 1942, Moss 1967) and elsewhere between New Figure 22. Geographic references in the Gulf of Maine region. Jersey and Cape Cod (Farrington 1939, 1949). The best season is tiiJ.- predictable. Sometimes the early season produces the best fishing, whereas in other years there is excellent fish- preponderant in 1962-1963. Giant school together in greater numbers ing in late summer and early fall, tuna have dominated the catches in than the larger ones. particularly in the grounds off N~ all the subsequent years (1964-1975), There has been a fairly close re- York Harbor. with only negligible numbers of small lationship between the occurrences The purse seine fishery began to and medium sized bluefin being re- of medium sized bluefin in Cape Cod harvest this stock in 1962. In the first corded between 1966 and 1970. As Bay and off Nova Scotia, but the three seasons (1962-1964) consider- in Newfoundland, the modal lengths important runs of small fish which able quantities of medium sized blue- of the giant bluefin taken in this area have occurred in the former arca have fin were taken, but in subsequent in the late 1960s reached high val- had no counterpart in the latter. years, fish of this group have been ues, over 220 cm, and the size of the The runs of sman bluefin in Cape rare in this area, as well as in the smallest fish taken increased signifi- Cod Bay have comprised ages 2-4, more northerly waters which they cantly. The latter trend changed in and we are aware of only one indi- formerly frequented (see above). 1970-1971, indicating some recruit- vidual of age 1 having been reported Trends in the catches are shown in ment of younger fish. In subsequent from this area. The age composition Figure 27. Wilson (1965) and years, however, the catches have con- . of these size groups has often over- Sakagawa (1976) give details of this sisted almost entirely of very large lapped, with age 4 fish associating fishery and its catches. fish, and the mean size has been with runs of medium fish, and age 5 The size composition data (Fig- steadily increasing. Catches of blue- fish with runs of small bluefin. ure 26) suggest some variation in the fin less than 8 years old have been sizes taken by the various gears. In insignificant. b. Cape Hatteras - Cape Cod the years when most of the data were (Coastal Waters) The available data for 1973-1975 from rod and reel catches, 1941-1960, The "Middle Atlantic Bight" show a continuing increase in the age 1 fish were often important. In (Figure 25) is the usual summer habi- size of the fish taken, especially by the years from 1962 on, when the tat of the small (age 1-4) bluefinof the hook and line and harpoon meth- seine fishery was the chief harvester the western North Atlantic, although ods. The average weights of fish of young b luefin in this area, age 1 they have occasionally ranged into caught by nets (traps and purse seines) fish were important only in some the Gulf of Maine (chiefly Cape Cod are somewhat lower, possibly becausc years, notably 1966. In the first three Bay) as notcd above. Many traps in of the tendency of smaller fish to years (1962-1964) of intensive seine this area took bluefin tuna occasion- fishing, fish of ages 4 and 5 were

25 30

. 1947 '20

-fa

0 30

20 .948

'10

~ 30 ...,J Cl. ~ 20 1949 ~ ~ 10 c;:) at 0 30

20 1950

0 30

20 1951

0 50 100 150 200 250 300 LENGTH (em)

Figure 23. Lengths of blue fin tuna captured in Maine and Ipswich Bay, Massachusetts ("+" on graph means less than 0.5%).

26 important. Many additional fish of Table 7. Landings data from the Commonwealth of Massachusetts in 1974. ages 5 and over were taken in this period but were discarded because Number Metric Average they were not acceptable to most of Gear of fish Tons Weight (kg) the canneries (several eyewitness re- Trap 37 9.1 245.6 ports, personal communications). Seine 167 48.1 287.5 Also many fish were lost when nets burst, or were discarded when the Rod and reel 200 63.5 317.5 catch exceeded the remaining carry- Harpoon and hand line 900 349.2 317.5 ing capacity of the vessels (the data sources are the same as above, in addition to incidents witnessed by some of the authors and their col- These sport catches of giant tuna were through October (Shingu et al. 1975). leagues). After 1966, fish of age 2 usually unimportant in numbers, but Shingu and Hisada (1976), however, usually dominated the catch. Since did document their seasonal occur- reported that medium-sized bluefin 1974 the New England based seiners rence in the area. tuna (ages 5-8) were scarce through- have generally avoided age 1 fish as At the other end of the size range, out the Atlantic Ocean. They also - a voluntary conservation measure. runs of very small (age 0) bluefin (1- noted that, during the winter months, Since midsummer 1975, their cap- 2 kg) occasionally occur in this area December-February, considerable ture has been prohibited in conform- from late July into October. These proportions of small fish (ages 2-5) ance with the ICCA T regulations. It are most common in late summet have appeared in the catches of re- appears, however, that in most years and early fall, and from northern New cent years in the waters off New En- full recruitment to the fishery does Jersey southward to Cape Hatteras. gland not occur until age 2. They are of no significance to the The size composition data give fishery, but the hiological informa- d. Bahamas and Southeastern Florida indications of strong-year classes. tion obtained from them has been a The only bluefin fishery in the The year class of 1938 was dominant very important step in understanding western Atlantic south of 35°N for in the New York Bight in 1941. In the life history of the species. 1951 the year class of 1950 showed which there is significant size com- up very strongly in the catches, but c. Atlantic Ocean outside 200 position data is the sport fishery off no sampling was carried out. It was meter contour N of 35°N the northwestern Bahamas (Cat Cay 0 very prominent, however, in the 1952 and Wof40 W and Bimini) (Figure 29). All the fish sample. The class of 1958 was con- During the cold season, the blue- taken are giants, over 185 cm and spicuous in the 1960 and 1962 fin tuna disappear from the summer 122 kg (Figure 30), and are caught samples. The class of 1965 was domi- habitats described above. Since 1956, in May and June. Usually the fish are nant in the 1966 seine fishery, and however, exploratory and commer- caught from schools which are trav- showed up strongly in 1967 and 1968. cial 10ngline activities have revealed elling northward along the edge of Data for 1974, 1975, and 1976 indi- much about their oceanic distribu- the Great Bahama Bank, but on rare cate a very strong year class of 1973. tion in this period (Wathne 1959, occasions they are taken from schools Sport fishing for giant bluefin Wilson and Bartlett 1967, Wise and which are "smashing" (feeding on off New York Harbor was fruitful in Davis 1973). The only substantial size the surface, often jumping clear of the 1930s (Farrington 1939), but de- composition data for oceanic bluefin the water) farther offshore. This fish- clined after World War II. Late in the tuna catches are from the area north ery has varied somewhat in recent 1940s, a new giant tuna ground was of 35°N and west of 400W (Figure years, with a general tendency to de- discovered near the western coast of 28). The most important exploratory cline. Many of the fish have been Rhode Island (Farrington 1949). This catches were near the northern edge released after being brought to the was productive for some years, but of the Gulf Stream in spring, and in boat. We have some weight records after 1960 successful seasons became the canyons along the edge of the for more reccnt years, however, infrequent. More recently, giant tuna continental shelf in fall (Mather and which, although few in number, con- have been caught farther off the Bartlett 1962). The majority of the stitute representative samples. These Rhode Island and eastern Long Is- fish taken were in the medium (120- samples indicate that the modal sizes land shores, in areas where the tunas 185 em) size range. As in the inshore and minimum sizes of the fish taken follow the nets of trawlers as they are fisheries, however, the average size in this fishery have increased steadily being hauled to the surface. This fish- of the fish taken, as well as the sizc in recent years Rivas (1976) showed ing has usually been most successful of the smallest fish taken, increased that the mean length of the males in late summer and early fall. After markedly during the 1960s. which he had measured in the years being absent for many years, some Japanese longline catches in this 1972-1973 at the Bahamas was 25 giant bluefin have been taken off area have indicated a predominance cm longer than the mean of those northern New Jersey or during the of the larger medium sized fish (about which he had measured in the years later part of some recent seasons. 100 kg) during the period from April 1952-1955. For the same periods, the

27 30

20 4947 10 l··.. O· r~ L-_ - """"""'t:::t1' = 20 1948 49~!!l

0 30

20 i_9 U'~6

10 . 't""t"4"lt ...... -..., ...• 0 "0 l l ...•~ 49~7 ..• 20 l:!> 10

++ --- .•...•.•• 0 .- 30 i959 20 '9Si:

0 30

20 1953 .960

0 50 tOO 150 20<> 250 300 !K) 100 150 200 2"0 300 L £N(;TH (.:_.1 LENGTH (.:•••)

20 '4961 1968

10 ~ 0 ....•.. 30

20 "962 1969

0 30 l 20 1963 ..,970

0 ~... 30 ::loO 1964 <:§ 20 1971 ~ 10 * 0 30 l 20 15ll'6~ '973

'0 <> - .•. --- .•. -- ....•..•..•. 30 l l 20 1966 1974

50° l 20 '967 1975-

0 ••0 100 "'0 200 30:> 30 '00 150 2.00 2"0 500 L E"IV(;TH t'CR'J,) .LeNGTH rc,"~

Figure 24. Lengths of bluefin tuna captured in Cape Cod, Massachusetts bays and vicinity (1947-1975) ("+" on graph means less than 0.5%).

28 been mainly in the Gulf of Mexico and the northwestern Caribbean. The Japanese effort, which has been much more extensive, has shown that the species occurs occasionally throughout most of the Caribbean (Fisheries Agency of Japan I967a). A small scale Cuban longline fishery for giant bluefm has operated in the spring, over the Bartlett Deep between Cuba and Jamaica. This fishery was initiated in 1969 and the largest catch of about 360 tons (including incidental catch of other species) was taken in 1970. The landings were smaller, but good, in the next three ~ CITIES years, but the 1974 catch was ex- @ GEOGRAPHICAL REFERENCES tremely poor (Ubeda 1974). Cuban I CHINCOTEAGUE 2 OCEAN CITy handliners occasionally catch giant 3 IIEACH HAVEN bluefin off Havana in the spring 4 BARNEGAT BAY :l BELMAR (Rivas 1954). 6 SHREWSBURY RKS. All of the longline catches in the 7'THE MUO HOLE" Gulf of Mexico and the Caribbean B BLOCK IS LAN 0 9 MARTHA'S VIIlEYARO Sea for which we have size data were 10 NAIiTUCKET giants, over 185 cm long. Similar I I CHATHAM size fish have been encounteredoc- casionally by sport fishermen between Cozumel Island and, the Yucatan Peninsula and off the Mis- sissippi delta in late spring on. the surface, sometimes in large schools (Nakamura and Rivas 1972). We had virtually no records of occurrences of medium sized or small bluefin tuna in these waters until Shingu et al. (1975) reported catches of bluefin tuna weighing less than 10 Figure 25. Geographic references for thc Cape Hatteras to Cape Cod areas. kg by Japanese longline vessels in the Gulf of Mexico in June and July 1973. We have had several reliable rep0l1s and records, however, show- mean length of the females which he and into early winter (Rivas 1954, ing that very small (age 0, 2 kg or had measured increased by 20. cm. Mather and Schuck 1960, Mather less) individuals have occurred in the Similar fishing occurs, with fewer 1963). boats participating, along the west- Gulf of Mexico from July into No- e. Gulf of Mexico and vember. ern edge of the Little Bahama Bank Caribbean Sea (West End to Matanilla Shoal). Bluefin tuna are caught by 3. Atlantic Oceanic Waters Giant bluefin have also been longline, and occasionally by sport Extensive data on the seasonal taken off the eastern Bahamas from fishing, in the Caribbean Sea and the distribution of blue fin tuna in the oce- Cat Island to Walker Cay (Anony- Gulf of Mexico (Figure 31). Catch anic waters of the Atlantic have be- mous 1962), in the same season. A records, aside from those of the Japa- come available from the records of few have been taken off southeastern nese longline fishery, and size data the Japanese longline fishery Florida on rare occasions during thc are sparse, but sufficient to give a (Shiohama et a!. 1965, Fisheries winter and spring. good idea of their distributional pat- Agency of Japan 1965, 1966, 1967a, Small and medium sized bluefin tern. Most of the catches have been 1967b, 1968, 1969,1970, 1971,1972, are very rare or nonexistent in the in the first two quarters of the year. 1973, 1974, 1975, 1976; Wise and vicinity of the Bahamas, but runs of United States exploratory catches Le Gucn 1969; Wise and Davis 1973) very small (less than 2 kg) fish some- (Wathne 1959, Anonymous 1962) as well as from exploratory fishing times occur off southeastern Florida and commercial catches (H. R. Bullis, (Wathne 1959, Anonymous 1962, in July-September, and individuals Jr., personal communication) have Wilson and Bartlett 1967). The gen- are sometimes taken through the fall

29 :so

0 ·30

0 30

lu 0 ~30 ~ ~ 20 ~ #.

{) .. 30

10.

0 50

+ 0 50 100 1!lO 200 30 LENGTH (emJ

0 50 100 150 200 250 LENGTH (em)

Figure 26. Lengths of bluefin tuna captured from Cape Hatteras to Cape Cod ("+" on graph means less than 0.5%).

30 eral seasonal distribution. pattern, 5 o NUMBER OF FISH lias 5 based on Japanese catch rates for 1956-1969, is illustrated by Figure 3 4 • METRIC TONS/10 4 32 (Wise and Davis 1973). This figure, however, includes southern blue- 3 fin, Thunnus maccoyii, as well as the 3 Atlantic bluefin, T. thynnus thynnus. The records south of latitude 20oS, 2 2 and perhaps also the one in the first quarter centered at l2°S, 2°E, are probably of southern bluefm. Catch rates for individual years and areas o o (Table 8, Figure 35) (J. P. Wise, 65 personal communication; Wise and Davis 1973) suggest that the abun- Figure 27. Annual catches of small and some medium size bluefm tuna from thc dance has varied considerably over northwest Atlantic purse seine fisheries, 1958-1973, in tens of thousands of fish the years. The catches declined pre- and thousands of tons.

I 30

'962 20 ".7 ~o l 0 30 l

20 1958 4963"-

0 30 l 1959 1964 •... 20 ~ :Il 10

~ 0 ••• ~ 30 l l - 20 1959 1966 10

0 30 l,- l

20 1960 10 Lt'" 0 30 zo 1960 t.IOv, 1967 10 r ol ~O tOO t~O 200 2~O 300 50 100 ,~o 200 250 300 LENCTH(cm) LENGTH (cm)

Figure 28. Lengths of bluefin tuna captured in the Atlantic outside the 200 mdcr contour north of 35° N and west of 40° W ("+" on graph means less than 0.5%).

31 cipitously from 1965 through 1970 laiMINIIS. :lORANGE GAY but have risen rapidly since then (Fig- 3WEST DID 4 OLD aAHAMA CIIlIN. ure 33) .. S CAY SilL aK. I; SIlNTIlIIEN CIIIlIl. The following description is T N. W. PROVIDENCE CHAN. • MIITANILU SH. based on the 1956-1968 catches (Fig- 9WIlLKER GAY ure 32): In the first quarter of the year, the highest catch rates occurred around the easternmost part of Bra- zil, and the greater Antilles. In the second quarter, the area of relatively high catch rates off Brazil extended farther to the northwest, and catch rates were high in the northern Gulf of Mexico, and off the Bahamas and the eastern United States. northward to latitude 400N and eastward to longitude 65°W. The concentrations off easternmost Brazil and off 85° the Bahamas appeared to be connected (Figure 32, Appendix Figure Figure 29. Geographic references for the Bahamas and southeastern Florida. 62 in Fisheries Agency of Japan

30 20 1939 t'~ to l

0 30 l

20 1947 ~9~2

0 4u 30

~ 20 ~948 1953 ~ ~ 10 * 0 30 l l

20 1949 1954

10 0 l 30 l

20 10 l"'O l···· 0 50 100 150 200 250 300 50 100 150 200 250 300 LENGTH (cm) LENGTH (em)

Figure 30. Lengths of bluefin tuna captured from the Bahamas ("+" on graph means less than 0.5%).

32 I 967a). Small areas of high catch • emu 30· • GEOUIIA'HICAL rates also occurred about midway be- IIIHIIIMen twecn castcrnmost South Amcrica and westernmost Africa. In the third quarter, the onlyar- eas of high catch rates were off New England and the Grand Banks of Newfoundland, and again in the narrow part of the Atlantic, midway between the most western part of Af- rica and the most eastern part of South America. In the last quarter, the concen- to· tration south of the Canadian banks was farther west and extended southward to latitude 300N. The concentra- IOOD tion between South America and Af- rica had moved northward to 20°- 32°N. The concentration off eastern- Figure 31. Geographical references for the Gulf of Mexico and Caribbean Sea. most Brazil had formed again, and

2lI' - W iii' iii' \.~ ~

41 f:)

f/' ;~e 1 .' 41 2lI' JUl~SEP

I.- lI' lI'

Figure 32. Distribution of oceanic catches of bluefin.tuna (per 10,000 hooks) in the filur quarters of the year, 1956- I968.

33 15 bluefm which were fished in Euro- pean waters in the warm season. CJ NUMBER OF FISH 110'1 The effect of these shifts in ef- • METRIC TONS/10& fort was to restore the catches to levels approaching those of the mid 1960s. Whether they will follow the to pattern of rapid rise and rapid decline illu~tra~ed for other areas by the combmatIon of Figures 34 and 35 remains to be seen. Shingu and Hisada (1976) showed the length compositions of 5 samples from longline catches taken in waters west of Gibraltar in May- August 1973 and April-June 1975. The former was dominated by large fish 190-240 cm long with a mode at 205-215 cm, but also included a o significant number of medium sized 1955 65 fish 135-155 cm long. Larger fish, 185-300 cm long with a broad mode Year at 225-255 cm, were even more preponderant in the latter sample, with Figure 33. Annual catches of Japanese longline fisheries in the Atlantic Ocean for only a scattering of fish 110-175 cm large and medimn size bluefin tuna in tens of thousands of fish and in thousands long. of tons. 4. Eastern Atlantic Islands Bluefin tuna occur in the vicinity of the Azores, Madeira, and the extended northward to 16°N, almost part of the North Atlantic south of Canary Islands (Figure 36), but joining the mid-ocean one men- 35°N, and in the Gulf of Mexico and there has been little information on tioned above. the Caribbean Sea, were giants, but the fisheries and the sizes of fish Considerable size data are avail- that there have been considerable until recently. able from exploratory fishing and numbers of medium sized, as well as commercial catches in the western giant, bluefm in mid ocean catches in a. Azores North Atlantic. These records indi- the 1960s (Shingu et al. 1975). Ferreira (1932) reported on the cate that most of the bluefin taken in After the decline of their Atlan- tuna fisheries of the Azores for the oceanic waters south of 35°N and tic bluefm tuna catches in the late years 1924-31. The principal catch westof700W (catches northof35°N 1960s and early 1970s, the Japanese was bigeye tuna, "Parathunnus and west of 400W have been dis- shifted much of their effort to the obesus", with bluefin tuna being cussed in a previous section) were eastern Atlantic and the Mediterra- much less frequent. giants. nean. The remaining effort in the Seven of 219 tunas caught in Unfortunately, little size data western Atlantic was concentrated in 1930 and 5 of 1404 caught in 1931 are available for the much more ex- the northern Gulf of Mexico in May were bluefin. The fishing seasons tensive Japanese catches. Hayasi et and June, when giant bluefin spawn usually extended from mid-April or al. (1970) reported that the Japa- there, and in the area south of the early May until July or August. nese longline fishery took "small" Grand Banks through much of the Ferreira does not state the sizes of bluefin off Florida (25°-35°N, 70°_ year (Shingu et al. 1975). fish taken, but mentions that very 80°W), but no size data have been The move into the eastern At- small (50 em) tunas occurred, as provided. Hayasi and Shingu (1972) lantic brought new pressure on stocks well as adults. Figure 5 in his work, and P. C. Wilson (personal commu- of larger fish which had previously which is described as a young nication) provided lengths for about been fished mainly by the declining "Parathunnus obesus" of 51 cm, 220 Atlantic bluefin caught in oce- trap and seine fisheries, and on me- shows, in our opinion, a young blue- anic waters. Most of these were gi- dium sized fish which had been pre- fin tuna. ants, but a considerable number were viously fished mainly by the Spanish During cruise 63-4 of the Bu- medium sized, although mostly of and French bait boats in the Bay of reau of Commercial Fisheries M/V the larger sizes (ages 7 and 8) oc- Biscay. The fishery also provided in- "Delaware", six giant bluefin were curring in that group. It appears that dications of a previously suspected taken by longline off the Azorean nearly all of the bluefin over one wintering ground around the Canary Island of Santa Maria in May 1963, year old taken in the westernmost Islands (Aloncle 1964) for the large and another was lost alongside the

34 Table 8. Catch rates (numbers of fish per 1,000 hooks) for bluelin tuna of the Japlmese Atlantic 10ngIinelishcry, 1956-71, by year and area. The BEN and RIO areas arc not included since it is believed that the bluefin caught in them were predominantly southern bluefin. Note: 0.00 = <0.005 but> 0; 0 = effort but no catch; - = no effort.

Year GM NOW NOE CAR GUI CV GG BAIl Total

1956 0.01 0 0.01 1957 0 0 0.14 0.11 0 0 0.07 1958 0 0.01 0.01 0.00 1.17 0.06 1959 0.51 0 0 0.19 0.08 0.00 0.94 0,22 1960 0 0 0 0.81 0.15 0.17 0.32 0.33 1961 0 0.13 0 1.11 0.08 0.01 0.36 0.16 1962 0.02 0.13 0.01 3.12 0.36 0.21 0.83 1.11 1963 0.02 0.18 0.05 0.03 3.94 0.25 0.01 3.82 1.42 1964 0.18 0.99 0.21 0.19 1.78 0.12 0 1.07 0.88 1965 0 2.98 0.16 0.07 0.76 0.07 0.00 0.26 0.76 1966 0.10 3.39 0.07 0.03 0.30 0.01 0.00 0.02 0.58 1967 0 0.72 0.03 0 0.11. 0.04 0.00 0.00 0.17 1968 0.31 0.34 0.02 om 0.02 0.00 0 0.00 0.08 1969 0.01 0.18 0 0.00 0.02 0.00 0 0.00 0.04 1970 0.00 0.04 0.06 0 0.02 0 0.00 0.02 0.02 1971 0 0.43 0.12 0 0.00 0.00 0 0 0.19 1956-71 TOTALS Thousands of Fish: 0.7 94.0 2.0 0.8 130.0 9.9 3.2 52.3 293.0 Millions of Hooks: 8.9 87.5 17.3 19.6 96.4 91.2 92.6 58.4 471.8 Fish per Thousand Hooks: 0.08 1.07 0.12 0.04 1.35 0.11 0.03 0.89 0.62

vessel (Anonymous 1963). In the from two size groups: 6-7 kg, and twice in two years, with 374 kg and same period, six bluefin tuna werc 150-200 kg (Aloncle 1966). 392 kg fish (Anonymous 1975, 1976). observed among the landings of the Several additional catches of large c. Canary Islands local fishery at Ponta Delgada, and bluefin, off Gran Canaria, were re- Early information (Frade 1929) all of these were also giants (obser- ported by C. H. Roncoroni (personal indicated that T. thynnus thynnus was vations by Dr. B. B. Collette, Dr. D. communications). It appears that most rather rare at the Canary Islands, but de Sylva, and F. J. Mather). of these giants were taken in late fall more recent developments indicate and winter (L. F. de Gamboa, per- b. Madeira that the species may occur there in sonal communication). The distribu- The numbers of blue fin tuna sold considerable numbers, and in vari- tion of Japanese winter (January- in the market in Funchal, Madeira, in ous sizes. Alonc1e (1964) reported a March) longline catches in 1974 the years 1954-1962 were furnished wintering area for small and young (Fisheries Agency of Japan 1976) in- by J. Maul (personal communication). adult bluefin tuna (0.5-60 kg) be- dicates that the Canary Islands are in These ranged from six to 268 fish per tween Lanzerote, one of the eastern- a wintering area for bluefin tuna .. year, averaging 104. The most nu- most of the Canaries, and the Moroc- Santos (1976, 1977a, 1977b) has merous landings were in March-June can coast. The senior author directed provided the first detailed informa- and in October, with the least in No- the tagging of four 45 cm (age 0) fish tion on commercial catches of blue- vember-January. Catches of other tu- 011 Gran Canaria in Decemher 1974. fin tuna in the Canary Islands. The nas, notably bigcye, were much more Catches of largc bluefin tuna have 1975 landings, excluding longline numerous. Maul has stated that thc bcen made by sport fishermen off catches, werc 932 metric tons. bluefin is relatively low in abundance Tenerife in the Canary Islands, where Catchcs and catch per unit of effort off Madeira, and that the catches arc the "European" record was broken were greatest in the period June-No-

35 • - EFFORT WITH CATCH X - EFFCRTWITHOUT CATCH .-._~.-X"GM . 4 3 2 1 •"

x X--e- ••.....• -.

Figure 34. Areas of the Atlantic Ocean (Wise and Davis 1973). )()(XXX - .•.----.. vember, peaking in August and September. In 1976, however, Santos reported that catches were frequent in the first four months, but declined during the summer. The estimated catch through September was 641 mt. 1. F. de Gamboa (personal communication, November, 1976) informed us that the sport fishing off Teneriffe • followed the same trend, and that the excellent fishing which had occurred in the fall of 1975 had not materialized in 1976. --. --.- •...... •-.-. 5. Eastern Atlantic Bluefin tuna fisheries in the eastern Atlantic (Figure 36) have been distributed in a manner )G •.•. -.-.--- •.•.•.••••• somewhat similar to those in the western Atlan- tic. Large and medium-sized individuals have been taken during summer and early fall in Nor- • wegian waters and the North Sea. The largest 3 fishery for small bluefm, with some mediums, has been in the Bay of Biscay, mainly in sum- 2 mer. Less important fisheries for small bluefin 0- /\ BAH 1 occur off Portugal in the fall, and off Morocco .. '\. . "'.-./ during much of the year. Trap fisheries in the / . o Ibero-Moroccan Bay have taken important - catches of large bluefin, along with usually lesser 2 amounts of medium and small individuals, in late spring and early summer...... • The fisheries in Norwegian waters and the I· '.---. TOTAL North Sea are of comparatively recent origin, as ,.-.- •...... • : '.--- o is the one for small bluefin off Morocco. The I I •. l . Bay of Biscay fishery is over a century old, but 1956 60 65 70 was modernized about 1950. The trap fisheries YEARS in the Ibero-Moroccan Bay, on the other hand, are of extremely ancient origin. Figure 35. Japanese longline catch rates of bluefm tuna in areas of The Japanese longline fishery has bccome active in the Bay of Biscay and the waters ofT the Atlantic Ocean. (Note: Bluefin in areas RIO and BEN are asSumed Gibraltar and northwestern Africa since 1970. to have been southern bluefin, 'l'hunnus maccoyii, while those in other areas arc assllilled to have been Atlantic bluefin 'l'hunnus .. " thynnus thynnus.) .

36 ing the catch and its size composition (Figure 37), has been described by Hamre (1971). The catch increased from a few hundred tons in the 1940s to over 11,000 tons in 1952, but decreased after 1962 to 2,500 tons or less per year. Hamre attributed the decrease to lack of recruitment. He showed that the seasonal movement of bluefin tuna through the fishery varied with age of fish. The largest fish (age 7 and older) arrived off 60· oc•.••" Bergen in early July and migrated to ,,1\C ••1\''' the northern Norwegian coast. After feeding there for three or four weeks, tCl1lll (t) G€OCAI'IlICM. IIIfIIIIIICU they migrated southward into the L-'-"L 1MVfIIl •.••• ...•.•.•--- - ..• bank area of the North Sea. Fish of I. ••••• 1J.1MUJI ages 6-12 arrived in mid-July south ..•._ ..."''''1 of 62°N latitude, and migrated south- ••---.-.. _UN--•••• ,,_ 2L_ ward along the coast. Catches of fish ..•._ u.~... •. of this size in late autumn by Swed- ILI--__ ------•• IL."" ...••.t..-a.. ish and Danish fishermen in the 12.•••••••• &If a••.•••. ILU~ 21 •••• _ •• Kattegat, including one fish which ••..a. •••• WI aIM ..ua. •. had been tagged earlier in the same season in Norwegian waters, indicated that the migration continued to that area. Five and six year old blue- 40· fin arrived in the southern area in September and migrated to the east coast of Norway (Skagerrak). This general pattern was followed as long as new year classes were recruited. Since 1958, when the 1952 year class was recruited, there has been no recruitment of younger age groups to the stock (Figures 37- 39). This resulted in a decline in the O· 20· annual catch, and a change in the migration pattern of the fish after the Figure 36. Geographic references in the eastern Atlantic. 1962 season. The largest bluefm now rarely migrate to the northward, but usually follow the southerly route previously travelled by the intermediate a. Northeastern Atlantic were observcd on the west edge of size (6-12 year old) fish. A few large Le Gall (1927, 1929) described Dogger Bank. In November and Dc- fish, however, were taken in the the distribution of blue fin in the north- cember, trawlers on the Great Sole at northern area in 1967-1969 (Figure eastern Atlantic and the North Sea the edge of the continental shelf en- 38). No bluefin have been caught in (Figure 36). The species was re- countered schools of them surfacing. the German North Sea fishery since corded in abundance off the south- Le Gall related the occurrences of 1962, probably because of this change west coast of Ireland in July and off bluefin in the North Sea and its tribu- in migratory pattern, but a few have the north coast in July and August. taries to the seasonal "transgressions" been caught in the Kattegat. Medium They were also observed off the west of Atlantic and Atlantic slope wa- sized bluefin have failed to appear in coast of Scotland in July, and off the ters, with salinities of about 35 0/00. the Norwegian fishery since 1962 south and west coasts of Norway, b. Nonvay (Figures 37-39). The annual catch and in the Skagerrak and the Kattegat Bluefin tuna have been taken by since 1967 has been less than 1,000 from July to October. Herring boats harpoon and angling gear in Norwe- tons. It fell· to a low of 90 tons in encountered them in July and Au- gian waters for many years, but the 1972 and even less in 1973. An in- gust east and south of Fair Isle, then introduction of the purse seine crease in the modal and minimum north and west of Dogger Bank. In method in the late 1940s greatly in- sizes of fish taken since 1957 is evi- late September and October, bluefin creased the catch. The fishery, includ- dent for both the northern and south-

37 em Norwegian areas, but is espe- o -----NORTHERN AREA cially striking for the southern area (Figure 39). • ----- SOUTHERN AREA 3 No. X 10 % of Sample c. North Sea The German bluefin tuna fish- 1956 ery in the North Sea was carried out 5 by handline, with the capture sometimes facilitated by an electrocuting o system (Meyer- Waarden 1951). The 10 landings reached a maximum of 1,286 tons in 1957 but declined to 5 1957 194 tons in 1962 (Tiews 1975). The fishery was then abandoned because of lack of fish. The catch consistcd o entirely of giant fish (Figure 40). An increase in the modal size of the fish 1958 taken since 1952 is apparent. A simi- 5 lar Danish fishery took catches of from 800 to 2,100 tons in thc years o 1950-1955, but became negligible 10 after 1959 (Tiews 1975). Small catches of bluefin tuna 5 1959 have been taken in the approaches to the Baltic by Danish fishermen using various gears. Yearly catches since o 1960 have been less than 200 tons. The fish taken have been large, with 1960 5 the modal size increasing in recent years. Sport fishing in the Oresund near Elsinore, Denmark, in 1948- o 1954 and 1960 produced yearly catches of from 18 to 119 iish with 5 1951 average weights of from 120 to 260 kg (L. R. Crandall, personal communication). o English sport fishermen have oc- 1962 casionally taken giant bluefin tuna in 5 the North Sea. The British Tunny Club (Anonymous 1937) reported that tuna appear off the Shetland Is- o 1963 lands III June and between 5 Scarborough and the Dogger Bank off the Yorkshire coast from July to o October. Sport catches in the latter area from 1932 to 1936 were listed as 21, 80, 54, 53, and 33, respec- 5 tively. The very difficult conditions for this sport, combined with the lack of fish in recent years, have prevented o its growth. 5 d. Bay of BiscllJ The most important fishery for small (2.5-35 kg) hluelin tuna in the o eastern North Atlantic has been in WEIGHT: 100 200 300 kg I • the Bay of Biscay (Figure 36). This AGE: 6 1 8 9 10 1\ 12 13 years Bay is therefore, presumably, the major nursery ground for young bluc- Figure 37. Weight distribution or bluelin tuna captured from Norwegian waters fin in the region and is a major source by area and year. 'lne eolumns to the left show number of fish landed with one of recruitment to the fisheries for me- unit equaling 5,000 fish (rrom Hamre 1971).

38 SO

20 1956 It&t

0 30

20 1957 1967

0 • •• 10 "-...• - ~ 20 '968 ~ ~ 10 It 0 30

1969 20 t9S9

0 50 100 150 200 30 LeNGTH (em I

20 1960

0 , I I l50 100 150 200 2~0 300 LeNGTH (em)

Figure 38. Lengths of bluefin tuna captured off Norway (north of 63°N) ("+" on graph means less than 0.5%).

dium sized and large blue fin in the bluefin usually being taken· inciden- Catches in the early 1970s have evi- eastern Atlantic. Considerable num- tally. The introduction of the live bait dently been somewhat over 2,000 bers of medium sized (32-122 kg) method in Spain and france in the tons per year. and some large bluefin have also been years 1947-1949 (Navaz 1950a, Bluefin tuna apparently occur in taken in the Bay of Biscay (Le Gall 1950b; de la Tourrasse 1951), how- the Bay of Biscay in every month of 1954, Shingu et al. 1975). ever, resulted in a specialized fishery the year (1. Le Gall 1950, 1954; French tuna landings from this for bluefin. The catches of this spe- Navaz I950b ), but the active fishing bay began about 1840, when pilot cies consequently increased greatly season has usually extended from boats from La Rochelle began taking in the 1950s, but were much lower Mayor early June into October or considerable catches of tuna by troll- through most of the 1960s and have November. Individuals weighing ing while waiting for ships. Tuna fish- remained at intermediate levels in the more than 30 kg are usually taken ing did not becomc important thcre 1970s (Figure 41). Statistics for this bctween mid-July and early Septem- commercially, however, until a crisis fishery are very confusing, but it ap- ber (Hamre and Tiews 1964, Hamre in the sardine fishery about 1860 pears that the landings varied between et al. 1966, 1968, 1971; Aloncle et caused the French tishermen to turn 1,000 and 1,500 tons in 1945-1949, al. 1974). their attention to tuna. The success of then rose to between 2,700 and 5,500 Research on bluefin tuna in the the trials exceeded expectations, and tons in 1949-1959. The catches in Bay of Biscay has been divided be- the fleet of sailing trollers increased the 1960s were much smaller, gener- tween two periods - 1949-1954 and year by year (Grandbesam;:on 1909). ally varying between 1,000 and 1,900 from 1972 to the present. This divi- The major catch of this fishery was tons, but attained 2,100 and 3,300 sion of research effort leaves a gap of albacore, Thunnus alalunga, with tons in 1965 and 1966, respectively.

39 30

1965 20 19!5!5

0 30 l t9!56 1966 20

·0 30

19&7 4967 20

0 30 l l

20 10 l"9 l t'.' 0 30

1959 1969 20 ••• ~ 10 :ill ~ 0 l!i 30 • 20 t970 10 l"OO

0 30 l

20 1961 t971

0 30

20 1962 1972

0 30 L l 20 It ..' 10 l'973

0 30

20 t964 1974

0 I I ~O 100 150 200 2~0 300 50 100 150 200 250 300 L£NGTH(cm) L£NGTH(cm)

Figure 39. Lengths of bluefin tuna captured off NOIway (south of 63°N) ("+" on graph means less than 0.5%).

40 3C1

20 1951 1957

0 30 .

20 1952 .9SI

0 30 l

20 tl53 Iu ~ 10 ~ 0 l- ~ 30 l ~ - 20 1954 '960 10

0 30

20 1955 61 ~o l..

0 30

20 1956 .962

0 !lO 100 150 200 250 300 50 100 150 200 250 300 L£NGTH(cm) LENGTH (cm)

Figure 40. Lengths forbluefin tuna captured from the NOl1hSea ("+" on graph means less than 0.5%).

almost two decades for which very the next in order, and age 1 fish oc- St. Jean de Luz, the principa,l port of few data are available. curring episodically in recent years the French bluefin tuna fishery, in Length frequency data in 5 cm (Dao and Bessineton 1974). Age 1 terms of fish weighing less than 30 groups for Bay of Biscay catches in fish were important in the 1949 kg and more than 30 kg (Hamre and 1949 (J. Le Gall 1950) (French sample, but no data for other years in Tiews 1964, Hamre et ai. 1966, 1968, catches only) and 1972 (Bard et ai. the peak period of the live-bait fish- 1971; Alonele et a1. 1974). Eighty 1973) and 1975 (Cort 1976) (for both ery are available. There has been a percent of the 1962-1972 landings French and Spanish catches) are pre- decrease in the importance of age 4 by weight were in the class weighing sented in Figure 42. Additional size and larger fish in the catches since less than 30 kg (Dao and Bessineton frequency data; in different size 1972. This has been attributed to the 1974). The percentage by numbers groups, are furnished by Dao and entry of Japanese longline vessels into would, of course, be considerably Bessineton (1974) and Cort and the area in 1974 and subsequent sea- higher. Cendrero (1975). sons (Cort and Cendrero 1975, Cort The Spanish fishermen, how- These data indicate that age 2 1976). ever, take more of the larger fish fish are usually the most important in Much additional data is avail- than the French. Dao and Bessineton the Bay of Biscay catches, with age 3 able for weekly (or daily) landings at (1974) found that only 52% of the

41 total French and Spanish catches of The 1965 catch is illustratcd by ages 2 and I, respectively, in the en- I 972 and 1973 consisted of fish thc lcngth frequencies of a 363-fish sumg summcr. weighing less than 30 kg, whereas sample tabulated by week of capture In November and December 67% and 80%, respectively, of the (weeks 40-46, September 26-Novem- 1960, lishing boats from Barbate, French catches for those years were ber 13). All of the 363 fish measured Spain, seined a great quantity of blue- offish weighing less than 30 kg. They were age 1; their total weight was fin about 42 cm long and 1.7 kg in found two apparent causes for this 2,047 kg and the average was 5.6 kg. weight, along with young albacore difference: The total catch of about 13,000 fish of about the same size (Rodriguez- - the French sought out the smaller weighing 75 tons was taken mainly Roda 1964a). A histogram of a fish, which command a higher between early October and early No- sample of 100 of these showed a pnce, vember. The 1966 catch was small range from 38 to 45 cm, with a mode - the baits used by the Spaniards and irregular (lnd was not reeordcd at 41. 9 cm. This author states that the were larger than those used by the (Hamre et al. 1968). In 1968, 26,199 fishermen of Barb ate often seine blue- French. [ish averaging 5 kg were taken lin of 40 to 60 cm in length off the In view of the virtual disappear- (Hamre et al. 1971). Moroccan coast from Larache to ance of medium sized bluefin tuna Casablanca and even to Safi and f. West coast of Morocco from the landings of the Norwegian Agadir in October, November and Small bluefin arc taken off the fishery since 1962, and their rela- December. west coast of Morocco by hook and tively poor showing in the trap fish- line, live bait, and seine fisheries (the eries of the Ibero-Moroccan Bay (sub- g. Ibero-Moroccan Bay Trap trap fishery will be discussed sepa- Fisheries part g of this section), it is unfortu- As noted prcviously, trap fisher- nate that size composition data for rately). Catches ranged up to 2,000 ies for bluefin tuna have existed in Spanish landings prior to 1972 are tons in the mid 1960s, but have been the Ibero-Moroccan Bay (Figures 44 not available. less than 1000 tons in recent years and 45) for centuries. The recorded In addition to the commercial (Figure 43). Fish are present during histories of the Spanish and Portu- fisheries, there has been an active most of the year, but the largest catches occur in autumn (Aloncle guese fisheries date back to the 15th sport fishery along the north coast of and 16th centuries, respectively Spain for bluefin tuna and albacore. 1964). Alonc1e (1966) gave the length (Pavesi 1889). On the other hand, we Reportedly (L. F. de Gamboa, M. R. composition of a 9 I-fish sample from have found no records of Moroccan BorreH, personal communications) Atlantic traps prior to the 20th cen- this fishery has declined greatly in a purse seine catch of700 kg of bluefin taken September 9, 1967, at tury. The Phoenicians and recent years because of lack of fish- 0 o Carthaginians who fished intensively ing success. In addition, giant blue- 30 40'N, lO 05'W (off Cape Ghir). for bluefin in all these areas in the fin have been taken by Michael and The lengths ranged from 50 to 67 em, with nearly all the samples in a pre-Christian era (Parona 1919), how- Helen Lerner in August 1947 off Trehurden (Normandy, France) modal group extending from 56 to ever, probably operated traps similar to those still in use (Thomazi 1947). (Farrington 1949) and in the Bay of 65 cm, and having its main peak at Biscay by the late Generalissimo 62 em. This indicatcs that nearly all The specialized tuna traps are very large and complex structures, Franco and Max Borrell (Max Borrell, the fish were age 1. Aloncle stated with a leader extending up to 5 km, personal communication). that bluefin of this age were common in the region at this season. This catch and sometimes even more, from the e. West Coast of Portugal was made ducing a series of experi- shore to the body of the trap. In many Small bluefin were taken by troll- mental cruises of the sciner cases an additional leader extends ing in the vicinity of Cape Espichel "Danguy," which extended from Sep- diagonally up to 2 km farther off- (south of Lisbon), Portugal, in late tembcr 1964 to July 1965, and cov- shore (Figure 46). Traps have been summer and early fall. The season ered the area bounded by the African described and illustrated by several usually started in September-Octo- coast from Tangier to Cape Bojador, authors (Pavesi 1889, Parona 1919, ber (Vilela and Monteiro 1961, the south coasts of Spain and Portu- Rodriguez-Roda 1964a, Sara 1964, quoted in Tiews 1963). In 1960 the gal, the Canary Islands, and the Ma- de Cristofaro 1970). Two basic types entire catch of 5,500 fish (34.65 tons), deira archipelago. of tuna traps have been used exten- averaging 6.3 kg, was taken in No- The first few weeks of the cruise sively, the "Atlimtic" or "Spanish" vember. The 1961 catch was 7,850 resulted in the eaptun; or age 0 and trap and the "Mediterranean" or "Si- fish totalling 36.01 tons (4.6 kg average I bluefin and sightings of age 2 cilian" trap. Fodera (1964) and de age) (Hamre and Tiews 1964). Both and possibly age 3 bludin The few Cristofaro (1970) described the de- years' catches consisted of a large bluefin taken by trolling during the sign, construction and relative advan- group of age I fish (50-70 ern) and a wintcr were in the 62-em class. In tages and disadvantages of each type. smaller group of age 2 fish (75-85 late April and early May two indi- The traps in the Ibero-Moroecan Bay em), as shown by histograms for each viduals, one 70 cm and one 43.5 cm were of the Atlantic type. year and a sample of 128 fish from long, were taken northeast of the Sal- Most of thc traps along the Span- September 1961 catches presented by vage Islands. These would have been ish and Portuguese coasts faced west Hamre and Tiews (1964). and lished thc "arrival" (eastward)

42 fish, with small ones (ages 1-2) significant in 1958 and 1959 only. o ~U~BER OF FISH 110" • ~E:TRIC TONSItO. Medium sized bluefm were dominant in 1957 and important in 5 1956, 1958, and 1959. Since 1960, however, giants have constituted 4 over 70 percent of each year's sample. One year class, probably 3 that of 1954, dominated the 2 samples for the years 1963-1965 (Rodriguez-Roda 1969b). Length frequency data are not available for thc Portuguese trap catches, o but the yearly catches for the years 1950 1931-1972 (Vilela and Cadima 1961, Hamre and Tiews 1964, Hamre et a1. 1966, 1968, 1971) Figure 41. Annual catches by Bay of Biscay fisheries for small and some medium are shown in the size groupings size bluefin tuna in hundreds of thousands of fish and in thousands of tons. traditionally used in this fishery (Figure 49). Fish of the "atuns" size were run from late April through June. Length frequency data for the usually dominant, but in three Some of these were reversed at the Spanish fishery for the years 1956- years the cachorretas, nearly the end of June and fished the "return" 1959,1961 and 1963-1975 are pre- same sizes as our "small" group, (westward) run in July and August. sented (Figure 48). The catch con- considerably outnumbered them. The Moroccan traps faced southward sisted mainly of medium and giant These fish were generally most and fished the "arrival" run, which was northward in that locality, only. 30 After the 1976 season it appeared that, of all these traps, only one or two located off the Spanish coast 20 1949 would continue to operate. These fisheries, and the biology of the fish which supply them, have 10 been the subject of a great many investigations and scientific papers. o Therc are two maxima in the fishery, one near the middle of the 30 "arrival" run, and the other near the middle of the "return" run. Spawn- 1972 ing is p~esumed to occur between these maxima (Sella 1929a, 1929b; Vilela 1960). Sella (l929b) provided generalized diagrams showing the variation of the catches with dates o ++ and the movements of the fish in the vicinity of the traps during the spawn- 30 ing cycle (Figure 47). For fish of the same length, those 20 taken in the "arrival" run average about 15% heavier than those taken in the "return" run (Rodriguez-Roda 10 1964b) (data from fish taken at Barbate, 1956-1961). Vilela et a1. (1960) found that females lost about o 21 percent of their weight between 50 100 150 200 250 the two runs, when most of the spawn- Length (em) ing takes place, while males lost only about 10 percent of their weight. Figure 42. Lengths of blucfm tuna captured from the Bay of Biscay ("+" on graph means less than 0.5%).

43 4 were taken at Cape Spartel, at the C] NU~BER OF FISH 11 0' entrance to the Strait and opposite Tarifa . • METRIC TOIiSr10' 3 Statistics for most of the Ibero- Moroccan Bay trap catch are shown in Figure 50. These do not include 2 all of the Moroccan catch. We were unable to obtain continuous data for the important trap at Cape Spartel (in 1 the former International zone of Tangier) for 193~-1953, or for the three more ephemeral traps near o Kenitra (in the former French Pro- 1960 65 70 tectorate) for 1939-1955. Therefore we have omitted their catches ,and Year used those of the Larache group (in the former Spanish Protectorate) to Figure 43. Number and weight of fish for the Morocco fisheries for small and rcpresent the Moroccan catch. The medium size bluefin tuna. catches of this group, which varied from one to five traps in the years numerous in late August (Vilela far east (near Gibraltar) the traps were 1927-1954 and stabilized at three 1960). The a1bacoras and atuarros located. The average was smallest in from 1955-1966, have been recorded, (ages 4-7, including most of our "me- the Portuguese traps, and the greatest in numbers of fish, for 1927 -1962 dium" group) were important in some in the trap at Tarifa, near Gibraltar. (Lozano Cabo 1958, Hamre et ill. years but, as has happened with the He reported that the average size of 1966)~ Data for subsequent years are medium group in most other areas, the bluefin taken in the Moroccan available, in various forms, in Aloricle have generally decreased in impor- traps was even greater than the aver- (1964), Collignon (1964,1965, 1966, tance in the most recent years. age of those taken at Tarifa. AloncIe 1967, 1968, 1969, 1972), Lambeouf Size composition data for Span- (1964) showed that in Morocco the (1972), and personal communications ish trap catches by week (Rodriguez- average weight of the fish caught also from M. Lamboeuf and R. Sara. Since Roda 1964b) showed a tendency for increased with the proximity of the 1966 only one or two of the Larache the largest individuals to be taken traps to Gibraltar. The largest fish traps, if any, have been set. Data for near the beginning of each "run." Aloncle (1964) observed the same tendency in the catches of the Mo- roccan traps. Similarly, Vilela (1960) t CITIES showed that the smaller tunas tended \!) GEOGRAPIlICAL REFERENCES L C.IANTA ••••• to be most important in the catches SPAIN 2. C. TUFALGAR toward the end of each run, but espe- 3. C.IPAUEL 4. STWAII 0 •. ~.ALTA. cially in the "return" run. 5. ClIIlAUAI •. ClUTA, ft AllIIN'" Vilela (1960) found 300 males 7. GULF OF vaLEZ •. AL8OIU.N .1. (38.1%) and 487 females (61.9%) in 9. C.1IU fORCAS- . a sample of the bluefin taken in the Portuguese fishery in the years 1958- 1960. There was little year-to-year variation from this proportion. There IBERO· 36° MOROCCAN BAY was also little difference between the 2 sex ratios for the "arrival" and "re- C III turn" runs, except in 1960, when the <.I C sample from the "arrival" run con- ..• sisted of 44.4% males and 55.6% fe- ;: males. Rodriguez-Roda (19Mb) pre- z ...•C sented the figures for the sexes deter- 34° .. mined from sampIcsofthe 1956-1961. C catches of the Barbate trap, and the 1961 catches of two others (Table 9) 10° 8° 6· 4' 2° Lozano Cabo (1958) pointed out that the average size of the bluciin caught in the Portuguese and Span- ish traps increased according to how Figure 44. Geographic references for the Ibera-Moroccan Bay area.

44 1959,1960,1961,1962,1963,1964, 38' 1965,1966,1967,1968,1969,1970, SPAIN 197 1) are believed to be complete. Five traps were set in most of the years 1931-1965, three in 1966-1968

C.ST. YINCINT and two in 1968-1972. Due to these discrepancies and omissions, the data in Figure 50 are not exact. They are IBERO- presented to illustrate trends in the MOROCCAN WESTERN BAY MEDITERRANEAN catches rather than exact totals. 36' SEA Pavesi (I889) estimated the tCITIES mean annual production of the Span- TRAP SYMBOLS ish traps for the period 1884-1887 at YUR LAST ~RIOD S' 'ISHID 70,000 tuna, or quintals (100 kg). He RI"ORTID SIT ARRIYAL RITURN BOTH derived a corresponding figure of 1920·1949 o o 30,000 tuna for the Portuguese traps. 1950·1971 @ I!l MOROCCO 1972- Roule (1917) calculated the average • • yearly catch of the Portuguese traps in the years 1896-1912 at 43,983 tuna. 34' In the period from 1930 through 1960, the Spanish catches occasion- 8' 6' 4' ally surpassed Pavesi's figures, with 106,000 fish in 1930,76,200 in 1943, Figure 45. Trap fishing locations for bluefin tuna in the Them-Moroccan Bay 63,500 in 1944 and 80,500 in 1949. area. The average for the period, about 55,000 fish per year, was considerably below Pavesi's figure. The Por- the Spanish traps, provided by catches, however, were relatively tuguese traps only attained Pavesi's Lozano Cabo (I 958), Rodriguez- small. From four to seven Spanish average of 30,000 fish in 1943, with Roda (I 964a, 1973, 1974), and "Atlantic" traps were listed for 1941- 32,400 fish, and never approached Aloncle et a!. (1976), are believed to 1971. Since then, only one or two, if the 1896-1912 average of nearly be complete, but are somewhat bi- any, have been set. The Portuguese 44,000 fish. The 1931-1960 average ased by the inclusion of some records data, provided by Vilela (1960), Lima of the Portuguese fishery was 17,400 of the La Linea trap, which is actu- Dias and Barraca (I 972) and fish per year. The Larache group in ally just inside the Mediterranean. Its Republica Portuguesa (1957, 1958, Morocco produced a peak catch of 29,000 fish in 1958 and averaged 13,500 fish per year for 1930-1960. The addition of the Cape Spartel and Kenitra catches would increase these figures considerably. Data for Mo- roccan catches before 1930 are too meager to permit any deductions in regard to long-term trends. The total annual catches of the samples of the three fisheries remained above 48,000 fish and 7,000 tons per year through 1962. A de- (b) cline which began in 1963 became disastrous after 1967. Estimated catches varied from 16,000 to 24,000 fish (2,400-4,300 tons) in 1963-1967, and fell to 700 to 12,600 fish (100 to ___ I_~~ 1,600 tons) in 1968-1973. The Ror- COAST tuguese traps caught just one fish in 1971 (Lima Dias and Barraca 1972) Figure 46. Schematic diagram of the t)'pe of specialized tuna trap used in the and only 176 kg in 1972 (Y. F. Thero-MoroccanBay area: (a) body of trap, divided into compartments, (b) leader Barraca, personal communication). from shore to trap, (c) leader extending offshore from trap. Solid lines show trap They have not been set since. In 1972, arranged to catch fish traveling from right to left. Dashed lines show trap the only Spanish trap set in the At- modified to catch fish traveling from left to right. lantic, Barbate, which had averaged

45 about 20,000 fish per year [rom] 946- Table 9. Sexes determined [rom samples of the 1956-1961 catches [rom the ] 961 (Sakagawa and Coan ] 974), 13arbatetrap, !md the I96] catches of two others took only 388 [ish and the company which had operated the Spanish traps Trap Barbate Sandi-Petri Isla Cristina since 1929 was dissolved (Rodriguez Males 403 123 46 Roda 1973). Barbate took 1,952 tuna Females 756 215 in 1973 (Rodriguez Roda 1974). Two 66 Moroccan traps, the only others set in the At]antic in that year, caught 12 fish (R. Sara, personal com- for centuries. The most important fished mainly [or bluefin which were munication). Two Moroccan traps traps were the large ones in the cen- too young to spawn, or which were were also set in 1974, but took only tral Meditcrranean. The majority of in the [ceding, rather than the spawn- seven bluefin (M. Lamboeuf, per- these fished the "an'ival" run in May ing, phase o[ their annual cycle. sonal communication). The situation and June; the remainder fished the Thercfore the fishing seasons of these had become such that when Barbate, "return" run in July and August. Some traps were not limited to the May- which had not been set in 1974, took of the smaller traps also fished thcse August spawning cyele, and extended 1,842 fish (less than one tenth of the migratory passages and similar runs through much of the year. These 1946-1961 average) in 1975, it was in the Bosphorus between the Sea of smaller traps for non-spawning tuna regarded as encouraging (Alonele et Marmara and the Black Sea. The ma- were widcly distributed along the coasts of the Mediterranean, but were aL 1976)! jority of the smaller traps, however, The decline in the Barbate catches was accompanied by a marked increase in the average weight, indicating that poor recruit- PERIOD OF REPRODUCTIVE BEHAVIOR ment to the fishery was a major cause ,. ., of the decreased catches. Although EMISSION & FERTILIZATION the annual catch fell from 19,000 fish DEPARTURE in ]961 to 2,500 in ]971, the average MOVE FROM weight per fish increased [rom ]45 COAST kg to 223 kg. (Sakagawa and Coan 100 1974). Rodriguez-Roda (1964a) had already noted the drastic decrease in c>< the numbers of the smaller bluefin li ~so 50 taken in the Spanish traps since 1953, !C ••. and attributed it to either a high mor- (.)0 tality on young fish in previous years, ~ 0 0 ARRIVAL RETURN or unknown variations in oceano- MAY & JUNE JULY & AUGUST graphic conditions which might have caused them to go elsewhere. h. Trends in Eastern Atlantic Fisheries The decline in the northeastern Atlantic fisheries for large and medium bluefin tuna is illustrated in Fig- ure 51. This trend has been reversed to some extent by improved catches off Norway, and more significantly by the entry of the Japanese longline fishery into the area in 1971 (Shingu and Hisada 1976). Concem has been expressed over heavy catches of very young blue[in as a possihle cause for the decline in the fisheries for larger individuals (Rodriguez-Roda 1964a, ARRIVAL RETURN TRAP TRAP 1964b, 1969d). MAY-JUNE JULY - AUGUST 6. Mediterranean and Black Seas The fixed trap has been the prime producer of bluefin tuna in the Medi- Figure 47. Schematic diagram of bluefm tuna movements in the vicinity of traps terranean Sea (Figures 52 and 53) during the spawning cycle.

46 so

20 "'1 to

0 l- 50 1M. 20 1857 to

0 so tHl 20 1951

0 :sO l •• 70 20 '"' 10

0 30 l ••• ~ l!!o t9lt tl11 "'II: fI) ~ 10 • 0 10 l

20 1M3 ~n to l

0 30 1173 20 1964

0 30 191~ 20 1965

0 ...... !l0 Of 00 I~O 200 Z:;O 300 30 l LENGTH (em)

20 1966 10 ... 0 !l0 tOO 1:\0 ZOO 2!l0 300 LENGTH (em)

Figure 48. Lengths of bluefin tuna captmed in the Spanish fishery (1956-1959, 1961, 1963-1975) ("+" on graph means less than 0.5%).

47 50

N = NUMBER OF TRAPS 5 • CACHORRETAS < 30 KG

[J ALBACORAS 30-49KG

~ ATUARROS 50-89 KG >- ....a: 9 ATUNS > 90KG :r ...!!! ... o z ...o «

YEAR Figure 49. Annual catches of the Portuguese trap fishery (Hamre and Tiews 1964, Hamre et al. 1966, 1968, 1971). most concentrated off France and Various types of nets, hook and a. Western Mediterranean what is now Yugoslavia (Pavcsi 1889, line gears, and harpoons have also Although located between the Parona 1919, Belloc 1961). heen used for hluefin tuna in many formerly important trap fisheries of The history of the Mediterranean parts of the McditelTancan-Black Sea the Ibem-Moroeean Bay and the cen- tuna traps dates to the pre-Christian system (Pavesi 1889, Parona 1919, tral Mediterranean, the bluefin tuna era. Thomazi (1947) believed that Doumcnge 1953, Iyigiingor 1957). fisheries of the western Mediterra- the Phoenicians introduced this Until recently, however, their catches nean have produced modest tonnages method throughout their colonies, and were small in comparison with those (Miyake et al.l 976), consisting that some of the French traps had of the traps. mainly of small and medium fish. probably operated continuously from Developments after World War Various gears have been used, some pre-Christian times until their demisc II have altered this situation drasti- of which arc of ancient origin. Oth- near the end of the 20th century. He cally. While the trap catches have ers have been introduced recently. thought that the Sicilian traps were declined catastrophically (Sara 1973), Among the most ancient are the traps, of equally early origin, but had fallen catches of small (Tilic 1954, Scaccini which were formerly wide-spread but into disuse during the Arab occupa- and Biancalana 1959, di Meglio now survive in a few locations off tion. The Normans revived the fish- 1962) and large (Paini 1975, Miyake Spain and Africa only (Parona 1919, ery soon after their conquest of the 1976) bluefin by purse scine havc Belloc 1961). Hook and line gears island toward the end of the 12th become important. Also, Japanesc and specialized nets have also been century (Pavesi 1889, Parona 1919, longlincrs took increasing quantities in use since long ago. Purse seine Thomazi 1947). The numbers of tuna of blucfin in the Mediterranean in and longline fishing have been,intro- traps operating in the Mediterranean thc years 1972-1974. The catch deduced in the area since World War II. declined greatly during the 19th and clined in 1975, when the Japanese Sport fishing has also developed there 20th centuries (Pavcsi 1889, Parona government prohibited thcir longline in this same period. 1919), and especially since I950 (de vessels from fishing in the Mediter- Thc French traps are of histori- Cristofaro 1970). ranean during the spawning season cal interest only. Thomazi (1947) Until recently, the major tuna as a conservation mcasure. stated that they reached their apogee traps in the central Mediterranean Meanwhile, promising sport fish- in the 17th century. Gourret (1894) have been of the "Sicilian" type. eries for bluefin tuna have developed reported those traps near Marseille Since World War II, however, chang- along the French and Spanish coasts took bluefin tuna from late July to ing conditions have caused the aban- from the mouth of the Rhone to late November. In 1851 there were donment of many traps and the con- Castellon and along the French aI)d 10 traps in the area, but in 1891 only version of others to the "Spanish" Italian Rivieras (Ligurian Sea), where three \\ere operating. Their catch of type, usually with modifications alhaeore are also taken (Gianelli bluefin in 1891 and 1892 (1,500- (Gaudilliere 1954, Fodera 1964, Sani 1969, Ccsareo 1972, M R. Borrcll, 2,000 fish, 41-43 tons) was about 1964, de Cristofaro 1970). !\.. Cesareo, L. F. de Gamboa, and E. half of the total catch in the same K. Harry, personal communications). area by other gears. Parona (1919)

48 PORTUGAL - fiSHERIES 15

o NUMBER OF FISH 1104 10 • METRIC TONS /103

5 5

o o 70

15 SPAIN - FISHERIES 15

10 to

5 5

o 1930 35 40 45 50 55 60 65 70 MOROCCO -FISHERIES 5 5

o o 1928 30 35 40 45 50 55 60 65 70 Yl'llr

Figure 50. Annual catches of Ibero-Moroccan Bay trap fishcries for bluefin tuna in tcns of thousands of fish and in thousands of tons.

showed locations for 23 traps, of traps was set, and it took no bluefin Yearly catches of bluefm tuna at which eight were active, along the tuna (Rey et al. 1977). Most of these La Linea since 1961 have ranged coast of Provence (France) between traps fished from early February to from 0 in 1968 up to 2,400 fish weigh- the mouth of the Rhone and Monaco. mid October, and took feeding (non- ing 340 tons in 1965. Their average Thomazi (1947), however, reported spawning) tuna. Other species were weights have varied from 128 to 186 that the last of the French traps dis- more important in their catches kg, probably excluding the numer- appeared between 1892 and 1900. (Belloc 196 1) ous age 0 (1 kg) fish which are taken The Spanish and Moroccan Return traps have heen set at La in some years (Rodriguez-Roda Mediterranean traps have taken only Linea; on the Spanish coast near 1964a, I964b, 1969d, 1973; Rey et small catches of bluefin tuna in rc- Gihraltar; at Ccuta, a Spanish city on al. 1977). cent years. Parona (1 919) showed 23 the opposite side of the Strait of The trap at Ceuta and those along trap locations, of which nine werc Gibraltar; and at three nearby loca- the Mediterranean coast of Morocco active, along the Spanish coast east tions on the Mediterranean coast of may be considered together. Only one of La Linea. Belloc (1961) listcd five Morocco (Bell oc I961, Sara 1964). or two of the Moroccan traps have in that area, with maximum annual These traps takc blucfin in July and fished in most recent years. The blue- catches of 60 tons of all species com- August, but again they depend mainly fin tuna catches have ranged up to a bined for a single trap in the years on other species. maximum of 172 tons for a trap, but 1954-1958. In 1975 only one of these have usually been 50 tons or less

49 (Collignon 1964, 1965, 1966, 1967, Twenty of these were reportedly more "thonnaires" or "thonaires," 1968, 1969, 1972; Lamboeuf 1972; than 4 years old, and weighed 12,500 "combrieres," "courantilles," and Crespo and Rey 1976; M. R. Borrell, kg. Pcrhaps there is an error in these "scinches." In some cases the same personal communication). Little figures, as the average weight would name was applied to various gears, information is available on the sizes be 625 kg. according to the locality. The name of bluefin taken. F. de Buen (1927) We have little information on "thonnaire" appears to have been used stated that 4-5 kg bluefin were taken the bluefin tuna trap fisheries of Al- for several types of gear. in the Ceuta trap in early winter. geria. Heldt (1932a) listed six traps Hook and line gears used off the Rodriguez-Roda (1964b, 1969c) es- set in 1930 and two in 1931, but with French coast were described or men- timated that 500,000 age 0 bluefin little success in most instances. Belloc tioned by du Hamel de Monceau were taken by the traps at Ceuta and (1961) named three in the vicinity of (1769-1782), Doumenge (1953), di Mediterranean Morocco and the Oran, and listed their individual Meglio (1962) and Farrugio (1977). Ceuta fishing fleet in September-Oc- yearly catches for 1953-1958. The These included longlines, trolling tober 1963, but stated that such ex- largest such catch was 69 tons (all gear, poles, and sport gear. Dieuzeide tremely numerous catches of these species) and thc average was about (1931) described handline fishing for fish were exceptional. Crespo and 30 tons (all species). large andmedium bluefin in the Bay Rey (1976) showed that the catches Specialized nets used off the of Castiglione, Algeria. Thomazi of age 0 bluefin were much greater French coast, and their catchcs, have (I 947) and Dieuzeide (1949) detailed numerically than all other sizes com- been described by du llamel de an interesting method of hook and bined in eight of the 14 seasons from Monceau (1769-1782), Doumenge line tuna fishing utilizing small fishes, 1961-1974, with significant highs in (1953), di Meglio (1962) and which had gathered around a moored 1963,1967 and 1973. Rey et al. Farrugio (1977). These included fixed branch of a tree, as live baits. They (1977) reported that 22 bluefin were and drifting gill nets and beach and reported that this method was used caught in the Ceuta trap in 1975. pelagic multiboat seines, called off the Mediterranean coasts of Spain and Morocco, as well as off Algeria. Recreational fishing for bluefin tuna has been developed off the Medi- 20 terranean coasts of France and Spain. o NUMBER OF FISH /104 Commercial fishermen have been catching medium and giant bluefin II METRIC TONS /103 by trolling with rod and reel gear off Port de Bouc, at the mouth of the Rhone, since 1959. The season ex- 15 tends from late June into early No- vember. Annual contests, in· which sport as well as commercial fishermen participate, have been held. In one which took place August 27-31, 1969, 15 boats landed 40 tuna with 10 an average weight of 105 kg, even though the weather permitted fishing on only two days. The largest bluefin taken weighed 220 kg. The above information is from Gianelli (1969). Another French port where recrea- 5 tional fishing is developing is La Grand Motte, on the Gulf of Lions, where tuna up to 30-40 kg are taken (Cesareo 1972). Sport fishing off the French Riviera will be discussed in the following subsection. 1955 Recreational fishing has also be- o come popular on the Spanish Yea •. Mediterranean coast at Rosas, near the French frontier, and at Castellon. Catches at Rosas include small tuna Figure 51. Annual catches of northeastern Atlantic fisheries for large and and giants of 150-180 kg (Cesareo medium size bluefm tuna (Scandinavian illld NOl1h Sea seine and htxlk-and-line 1972). Tuna tournaments are held fisheries and lbero-Moroccan Bay trap lishelY) in tens of thousands of lish and in annually at Castellon in late August thousands of tons. and carly September. Catches totaled

50 ~CITI£S G)GE08ItAPHICA1. RI£FERENCU LGI_T_ 1••Lle••••• I.CASJUUlIl •• IALIMlCIS. s.~ LClllDA 7.COlI~j1 io);'~,~~...••• ', •., :.. .."SICILT- 10••••••••• li.gllnlE 40" 11.ISTIUl.UI, n,CIIEft ••••ClPIlUS "~0f'.11I_ ••.. MAI,. .• ,.," ~ • •7.AUllAJIDII'" 1 24 ,.. ' . " ; .. S " (I" ,::: ,.,', ',";";,a.,,, . 'lf1S:',: '. d._POLl....1- • '.' ""v .' . a..TUIIIS ' •••. ' :.' .. 21.o\I.CIIII5 • § ... 12.GI&F Of' casnCLlD1C :.~- D.GULFlW_U : • 300 aa,OUIl LIBYA

Figure 52. Geographic references for the Mediterranean and Black Seas.

~CITIE5 G>GEOGRAPHICAL REFERENCES 45. 1.ROSAS •• ST. TROPEZ 2.PORT \lINDItQ •• NICI 3.LIUCATI 10. MONACO 4.SETE n.IAN •• 0 S.PALAVAS 12.CAPO DELLE MELI e. PORT DE BOUC U.OENOA 44' 7.MARSEILLE 14.ELBA IS.

42·

12 O' •• 6' •

Figure 53. Geographic references for the northwestern Meditc'ITanean Sea.

47 fish weighing 4,536 kg with maxi- (M. R. Borrell and E. K. Harry, per- tember, but after they disappeared, mum, average and minimum weights sonal communications). In 1976, great quantities of age a bluefin of 161, 96.5 and 38.2 kg, respec- however, only one fish was caught (about 1 kg) were taken from late tively, in 1973, and 32 fish with maxi- (L. F. de Gamboa, personal com- September to early November (1. mum, and minimum weights of 180 munication), Tuna of the above sizes Bexnat Ortiz, personal communica- and 37.8 kg, respectively, in 1974 were taken in August and early Sep- tion),

51 The authorization of seining for to Capo delle Mc1e) from July to late Spain, Laboratorio Oecanografico bluefin tuna in Freneh Mediterranean September or early October. Palma ct al (1976) do not mention waters in 1960 brought about a con- Farrugio (1977) described the seining, even among the minor gears. siderable increase in the catches of seine fishing areas. In the Gulf of Rodriguez-Roda (1964a), however, the species. The development of the Lions, fish were taken in September noted that considerable numbers of fishery in the Gulf of Lions was de- and October in two areas, one be- age 0 blue fin (0.5 kg in September, scribed by di Meglio (1962) and tween Port Vendres and Leueate and Oetobcr; 1 kg in November, and 2 kg Farrugio (1977). Some old boats, the other between Sete and Marseille. in December) were often taken by mainly trawlers, were fitted with this Beginning in November or Decem- sardine seiners off Alieante, Spain, gear. The first seines, "eineiole", were ber, they tend to concentrate in the mixed in with the sardines. Consid- derived from the Italian type and' the northern part of the Gulf, between erable catches of age 0 bluefin in the second, "cerco", from the Portuguese Sete and the mouth of the Rhone. At same season during 1976 were also type used off Morocco. The annual all seasons, the fish are generally less reported (F. L de Gamboa and J. catch in the Gulf of Lions immedi- than 20 miles (33.3 km) from the Bexnat Ortiz, personal communica- ately increased from about 500 tons coasts, in waters whose depths rarely tions). Rodriguez-Roda (I 964b) also in the years 1950-1 961 to about 1,000 exceed 100 m. Off Provence and in reported considerable catches of age tons in 1961 and J 962 (Maurin 1964). the Gulf of Genoa, the fishing occurs o bluefin in the fall of 1963 off the Most of the 1962 catch was taken in from 5 to 50 miles (8.3 to 83 km) off Mediterranean coast of Morocco by the beginning of the year in the re- the coast between Cap de S. Tropez Spanish seiners based at Ceuta. gion of Marseille and Rousillon. The and Capo delle Mele. Spanish and Japanese longline French seine fishery for bluefin off Until recently, little infOlmation vessels have also taken bluefin tuna Provence and in the Gulf of Genoa on the sizes of fish taken in these in the western Mediterranean. An- began in 1967 (Patania 1967) and fisheries has been available. Gourret nual catches of the Spanish Mediter- has produced more than half of the (1894) showed that the average sizes ranean longline fleet, which fishes total French Mediterranean catches of bluefin taken near Marseille in primarily" for broadbill swordfish, of this species since then (Farrugio 1891 and 1892 by traps and other Xiphias gladius Linnaeus (1758), in- 1977). Hamre et a1. (1971) reported gears ranged from 18 to 28 kg. cluded from 16 to 274 tons ofbluefm that from July 1969 through January Samples of catches taken in the Gulf in the years 1968-1 974 (Laboratorio 1970 purse seine catches off the of Lions (off Languedoc, France) in Oeeanografico Palma et al 1976). Mediterranean coast of France to- 1953 and 1954 consisted of blue fin Japanese longliners took 238, 427 talled 1,500 tons, with most catches of ages I, 2, 3, and 4 (about 48, 80, and 7,980 bluefin tuna in Mediterra- occurring in October and November. 97 and 119 cm long, respectively) nean waters' west of longitude 100E Catches have fluctuated around I ,500 (Doumenge and Lahaye 1958). Little in 1972, 1973, and 1974, respectively. tons since 1966 with lows of I, 100 variation in sizes of fish with method Fish were 'eaught from April into tons in 1970 and 1972 !,lnda high of of capture was indicated by either of October, with the highest catch rates, 2,200 tons in 1971 (Farrugio 1977). these studies. Samples of the 1968 up to 24 fish per 1,000 hooks, occur- Miyake et a1. (1976) reported gener- and 1969 catches showed that most ring in JUne. Good catch rates ;,vere ally smaller catches in this period. of the fish were in the "small" size also attained in May and August For some years, their figures differed group, with age 3 dominant in both (Fisheries Agency of Japan 1974, considerably from those of Farrugio ycars (Figure 54). Since then, this 1975, 1976). (1977). predominance of age 3 fish has re- Rodriguez-Roda (1969d) ex- The best pre-seining fishing in maincd relatively constant (Figure pressed concern over massi ve catches the Gulf of Lions was from early 55). In 1970 and 1971 a significant of very young bluefin in the western April to mid-June and from late July showing of mcdium (agcs 6-8) and Mediterranean, as well as off the At- to the end of September, with a lull small giant (ages 8-10+) bluefin oc- lantic coast of Morocco, which he from mid-June to mid-July. Scattered curred but this has not happened since had described previously (Rodriguez- fish were caught in late February and (Farrugio 1977). The 1971 catch eon- Roda 1964a, I964b). He reported March, and from October into early sistcd partially of 120 Ions of bluefin catches of large numbers of age 0 December. Late December and Janu- wcighing from 100 to 150 kg (ages fish in the fall by seiners off Alieante ary were periods of scarcity 8-10), which were reportedly taken and the trap at La Linea in Spain, and (Doumenge 1953). Data on the 1%3- off Sete, France, in J\pril by three by seiners and traps off the Mediter- 1965 catches (Hamre et al. 1968) sardine-tuna seiners (J\nonymous ranean coast of J\frica just east of showed minor peaks in March and 1971). The possibilities of seining Gihraltar. He reported that, in the major peaks in Septcmber-October. bluclln off the MedilelTanean coast period September IS-October 19, Farrugio (1977) reported that the of Spain were mentioned by Bellon 1963, about 500,000 age 0 bluefin seine fishery was active in the Gulf (1954), but, apparently, they have not were taken by the Ceuta seiners and of Lions from carly March to latc been developed signilieanlly. In their the traps in the vicinity. This was, May and fTom October into Dceem- review of the fisheries for tunas and however, an exceptional year, accord- ber and in the eastern area (St. Tropez relatcd species in the Mediterranean ing to his informant. We have been and Atlantic watcrs off southern advised that comparable catches of

52 age 0 bluefin were taken off 30 Castellon, Spain, in the fall of 1976, tpainly by sardine seiners, but also t968 by sport fishing boats. Rodrlguez- 20 Roda (1969d) believed that thc decline in the Spanish Atlantic trap fish- 10 eries for larger bluefin might have ""...., been caused by excessive fishing of immature fish. ~ 0 'q Bluefm tuna catches in the west- ~ 30 ern Mediterranean were evidently un- I.&.. important prior to the development c;:) 1969 of the French seine fishery in 1960. 20 Combining the data of Miyake et al. ~ (1976) and the Fisheries Agency of Japan (1974, 1975, 1976), it appears 10 that the total western Mediterranean catches varied between 1,000 and 2,500 tons (approximately) in the 0 100 150 200 years 1965-1973, but rose to about 50 4,200 tons in 1974. The latter figure LENGTH (em) was due mainly to exceptionally large catches by the French purse seine Figure 54. Lengths of bluefm tuna captured in France in 1968 and 1%9 ("+" on and Japanese longline fisheries. The graph means less than 0.5%). fishing of age 0 bluefin in this area, which apparently is very poorly recorded, appears to be a cause for concern. b. Central Mediterranean 1970s, the traps were failing (Sara showed locations for some 100 traps The central Mediterranean (Fig- 1973) and the purse seiners were be- in Italian waters. These included ure 56) has traditionally been the coming dominant (Paini 1975, many which were inactive or unim- area of the major bluefin tuna catches Miyake 1976). Catches of the Japa- portant, or did not fish specifically in that Sea. The tuna trap has been nese longline fishery increased from for bluefin tuna (Sara 1968). By 1950, the dominant gear in the area until 1972 through 1974, but conservation only 30 real tuna traps were active, recently. The oldest trap fisheries measures which were introduced in only 14 in 1965 (de Cristofaro 1970) were around Sicily and Sardinia, and 1975 curtailed the catch in that year and just seven in 1973 (Miyake 1976; off the southwestern coast of Italy (Kume 1977). Italian longliners R. Sara, personal communication). itself. Additional traps were subse- whose primary catch is broadbill Catches of the Sicilian and quently installed off Tunisia and swordfish also take some bluefin tuna Sardinian traps for 1938-1939 and western Libya. All of these traps were (Sara and Arena 1967). 1946-1973, based on statistics from originally of the Sicilian type (Fodera Most of the major traps, located the Instituto Centrale di Statistica 1964). Changing conditions have ne- off the coasts of southwestern Italy, (1949,1951,1954,1957,1960,1963, cessitated their modernization Sardinia, Sicily, Tunisia and Libya, 1966, 1969, 1972, 1974) are shown through the use of better materials fished the arrival (prespawning) run in Table 10. Although data from and the adoption of the Spanish de- of maturing bluefin in May and June. sources which are probably more ac- sign. This process began in Tunisia A few, along the eastern and south- curate are available for certain years, in 1950 (Anonymous 1952) and in ern coasts of Sicily, fished the return this extensive series of records seems Sicily in 1956 (de Cristofaro 1970). (postspawning) run of spent fish in most suitable for illustrating the long- In addition to the ancient trap fisher- July and August. Most of the smaller term trends in the catches. A few ies(Pavesi 1889,Parona 1919,Belloc traps fished "erratic" or feeding blue- traps in the Gulf of Sant' Eufemia, 1961, Sara 1964), bluefin tuna are fin at various localities off the Italian Calabria, (Figure 56) also caught taken in the central Mediterranean mainland and Yugoslavia. The Medi- prespawning tuna. Three of them for- by purse seine (Scaccini and terranean trap fisheries have been de- merly took very large numbers of Biancalana 1959, Paini 1975), hook scribed and discussed by Cetti (1777), small fish. Pavesi' s (1889) data show aJld line (Scordia 1931, 1932; Pavesi (1889), Parona (1919), Sella that the average annual catch per trap Genovese 1965; Cesareo 1967) har- (1929a, I 929b, 1932a, 1932b), Belloc for two of these was 4,674 fish with poon (Scordia 1932, Sara 1968) and (1961), Sara (1964), de Cristofaro an average weight of 44.4 kg, or 208 longline (Sara and Arena 1967, (1970) and others. Parona (1919) (this tons, in 1879-1883. Parona (1919) Shingu et a!. 1975). In the early work was actually completed in 1914) listed seven armual catches of over

53 90 good period, as 68,029 tuna, probably at least 6,000 tons. The catches for 1894-1914 varied between 1 624 . and 8,160 tons, with an averag'e of 1911 50 50 4,643 tons (Parona 1919). Roule

0/0 (1917a) showed that the Sicilian and 0/0 Sardinian traps took totals of from 10 10 2,342 to 5,329 tons per year in 1909- 1913. Sella (1927) listed the Sicilian 1 2 3 4 5 6 1 8 910+ I 234 561 8 9 lOt and Sardinian catches in 1926 in a period which was then regard~d as 1965 50 1912 50 disastrous, as 9,800 fish.

"/0 0/0 The catches in 1938-1939 and 1946-1969, while not approaching the 10 10 pre-World War I levels, were generally better than those of the crisis 1 2 3 4 561 8 910+ 1 2 345678 9 10+ period in the late 1920s and early 80 80 1967 1973 1930s. The catch did not decline in proportion to number of traps fishing, partly because the least efficient 50 50 traps dropped out, and the most pro- % % ductive ones were improved (de Cristofaro 1970). The catches dete- 10 10 riorated drastically after 1969. Fig- ures for the Sicilian and Sardinian 1 2 3 4 5 6 7 8 9 10+ I 2345678 9 10+ traps for 1970-1975 provided by P. 90 Arena and R. Sara (Miyake 1976) 80 and for the Sicilian traps in 1976 (p. 1969 1974 Arena, personal communication), which differ considerably from those 50 50 in the Annuario Statistico Italiano for % % 1970-1972, are shown in Table 13. These data show considerably smaller 10 10 catches than those indicated in Table 10, especially in numbers of fish for 1 2 345678 9 10+ 1 2 34 9 10+ 1970-1972, and correspondingly higher average weights in those years. 1970 These figures indicate that the great- 50 est decline in the Italian trap fishery % % was accompanied by a great increase in the average weight of the fish 10 taken, just as it was in the Spanish fishery. 1 2 3 4 5 6 1 8 9 10+ 1 234 5 6 7 8 9 10+ The failure of the Italian trap AGE AGE fisheries (Table 12) has followed a Figure 55. Estimated age composition of samples of bluefin tuna taken in France rather distinct geographical pattern, moving from east to west. The first in 1964-1965,1967, and 1969-1975. order (Table 11) trap of Pizzo, the last one set in the Gulf of Sant' 100 tons (129-260 tons) for one of duction in the years 1879-1883 in Eufemia (compartment of Catanzaro, them in the period 1896-1914. One Table 11. Pavesi (1889) used the lat- Calabria), was abandoned after 1963. or two of these traps were set in each ter figures as a basis for classifying Another previously productive group of the years 1938-1939 and 1946- the Italian traps in orders as shown in in the Gulf of Patti (compartment of 1963 (Annuario Statistico Italiano). Table 12: Messina, northeastern Sicily), virtu- Their annual catch per trap varied The trap catches have been di- ally ceased operating after 1967. One from 25 to 1,329 fish, averaging from minishing gradually over a long pe- of them, San Giorgio, was set for the 16 to 65 kg each, or 0.4 to 75 tons. riod, but this decline became cata- last time in 1973, after nine years of The numbers of fish caught by the strophic in the 1970s.Pavesi (1889) inactivity, but took only five fish (R. more important traps in recent years reported the average annual catch of Sara, personal communication). The are compared with their average pro- these traps in the years 1879-1883, a group of return traps off the east coast

54 .. ,," mance (2,000 fish per year) (Pavesi ... ~ 1889) since 1970 (Table 11), 'Z"•• ", '"f. Pollution and the disturbing ef- /,. . ':','!',:,-, fects of increased coastal traffic and ';' .. ~CITIES

D b advised us that the 1974 catch of the :36 ~ MALTA three southwestern Sardinian traps was only 300 tuna. He noted that the entire coast had been contaminated .9. MISUIUlTA 24.IIA5 IlAPUDIA with the wastes of an aluminum plant. 2O.ZUTEN (BOADJ KAOIOJA) 25. MOItASTllI The sizes of fish taken varied 21. ZUAU 211.CAPE liON 22. DJ£1I11A II. with the location of the traps, or with Z7.IIIZEIlTE 23.CULF OF GAllES Z•• SKElIlllllAtlll the water temperature at the traps during the fishing season (Sella 1929a) as well as from year to year. Sella (1929a, 1932a) considered the traps off western Sicily and those off southwestern Sardinia as "cold" traps (surface temperature 18.0-19.0°C, 15° salinity 37.37-37.65 0/00) and producers of large fish, and those off Figure 56. Geographic references for the central Mediterranean area. Calabria and Tripolitania as 'hot" traps (surface temperature 20.8- 21.8°C, salinity 37.48-37,66 0/00) . of Sicily also became extinct after its and two in the Aegades Islands west and producers of medium sized and two most productive ones, including of there, as the only survivors of the small fish. The relationships between the first order trap of Marzameni, once flourishing Sicilian trap fish- occurrences of tuna in traps and en- took little or nothing in 1969. Less ery. In Sardinia, the first order trap vironmental conditions are discussed important return traps on the south- of Saline (compartment of Sassari, at in detail in section VI. ern coast of Sicily had failed in the the northwestern tip of the island) The numbers and weights of the 1950s. One at a new location off Cape took very poor catches (1-366 fish bluefin tuna taken by traps in each Granitola, at the southwestern comer per year) in 1967 -1972, and evidently compartment of Italy in each of the of Sicily, fished successfully through has not been set since. The three first years 1951-1957 were presented by 1966. After poor seasons in 1967- order traps of the Carlofortc group de Cristofaro (1970). The mean 1969, it was set for the last time in (department of Cagliari, southwest- weights of the fish taken in each 1972 with no success (R. Sara, per- ern Sardinia) averaged about 1,000 compartment in each year were cal- sonal communication). Its failure fish each per year through 1971, but culated from these data. The maxi- marked the end of the Sicilian return took only 1,174 tuna in all in 1972. mum, minimum and average of these fishery. The last traps in the Palermo In 1973, only two were set, and they mean weights over this period, for (northwestern Sicily) district were caught only 295 fish. The first order each compartment which contained also abandoned after the 1972 sea- trap (5,000 fish per year) of important tuna traps, are shown in son (R. Sara, personal communica- Favignana in the Aegadcs Islands is Table 14. tion). This left two or three traps be- the only one in Italy whieh has evcn These data support Sella's ing set each year in the Trapani dis- come close to a second ordcr pClfor- (1929a) findings in regard to western trict at the western tip of the island, Sicily and Calabria, but the traps off

55 Table 10. Number and weight of bluefin tuna caught in traps olT Sil.:ilyand Sardinia by Yl.:aras reported by the Instituto Centrale di Statistiea.

Year Traps Fish Tons Fish Tons AverageWt. (xlOOO) (xl 000) per Trap per Trap (kg)

1938 25 16.7 1.6 667 63 95 1939 29 17.4 1.6 600 54 89 1946 32 21.2 2.1 662 64 97 1947 28 20.3 2.1 724 75 104 1948 30 11.4 1.1 381 35 93 1949 32 18.1 2.1 565 67 118 1950 31 1&.2 1.7 588 56 95 1951 30 19.3 1.8 644 61 94 1952 29 9.4 1.0 324 33 103 1953 30 13.3 2.0 443 65 147 1954 27 12.2 1.7 451 62 138 1955 28 12.5 1.5 447 54 121 1956 25 10.8 1.5 434 60 139 1957 22 15.2 2.5 694 112 162 1958 27 17.9 2:6 663 96 146 1959 24 13.5 1.8 566 74 131 1960 21 11.7 1.2 560 58 104 1961 21 11.6 1.4 553 67 122 1962 19 12.5 \.3 661 66 100 1963 17 2.2 1.2 540 71 132 1964 15 12.3 1.4 819 106 130 1965 14 10.2 \.3 732 122 89 1966 15 9.2 0.9 611 62 102 1967 13 16.4 1.9 1,63 148 118 1968 13 13.2 1.7 1,016 132 130 1969 12 8.9 1.3 741 109 148 1970 9 6.6 1.0 733 106 144 1971 9 6.8 1.0 852 115 151 1972 8 4.6 0.8 576 103 120 1973 7 1.6 0.4 236 52 219

Sources: Instituto Centraledi Statistica 1949, 1951,1954,1957,1960,1963,19661969,1972,1974.

southwestern Sardinia did not pro- sometimes as high as 90%. When the crease in fishing effort during the dUl.:eespecially large fish in this latcr catches of large tuna were poor, as war. In 1964, these fish appeared period. they often were, substanlial catches again in the catches, increasing year Sara (1965c, 1968) discussed the of golfitani kept the fishcl)' solvent. by year. Sara thought that this occur- historical importancc of thc smaller About 1925, the catchl.:s of these fish rence was not transitory, because of bluefin (40-50 kg, ages 5-6) locally began to decrease gradually until they the local abundance of helTing, an- known as "golfitani" (Celli 1777) in virtually ceased about 1935. This chovies and mackcrel, on which they the Italian trap fisheries. In the years caused a real crisis in the industry. In fed. Consequently he believed that before 1920, when the fisheries were 1943-1945 (the first post-war years) the future of the trap fishery was flourishing, these smaller fish formed there was a transitory appearance/of good. Sara (personal communication, a large percentage of the captures, golfitani possibly because of the de- 1973), however, reported that the

56 Table 11. Italian traps grouped in orders according to the average number offish caught in 1879-1883 and their catches innumbers of fish since 1966. Only the first three orders are shown.

Order Average Average Last Record' Maximum Trap Location 1879-83 Year Catch 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976

First Order Saline NWSardinia 7,719 77 368 204 165 58 X Porto Paglia SWSardinia 4,423 1,425b 200 50 Porto Scuso SWSardinia 6,597 3,769c 3,862c 3,060c 2,778c 1,174c 15 0 5,000 Avg. IsolaPiana SWSardinia 5,691 2,100 364 250 Pizzo SWItaly 5,641 1963 26 X X X X X X X X X X Marzameni SWSicily 4,939 70 X 0 X X X X X X X 10,000 Max. Favignana WSicily 9,018b 4,217 3,250 2,894 1,368 2,340 2,023 970 1,772 2,0891,436

Second Order Bivona SWItaly 3,702 1953 X X X X X X X X X X 2,000Avg. Flumentorgiu WSardinia 2,165 1939 505 X X X X X X X X X X 5,000 Max Formica WSicily -,- b 2,359 1,997 1,094 980 1,197 505 184 594 960 503

VI -.)

Third Order Marciana Elba 1,810 Scopello NWSicily 1,000 792 372 178 279 372 270 68 X 203 600 1,000 Avg. Solanto NWSicily 2,000 1961 220 X X X X Oliveri NESicily 1,000 105 X X X X X X X X X 3000- Santa Panagia SESici1y 1,392 1959 27 X X X X X X X X X X 4,000 Max Cape Passero SESicily 1,851 X X 0 X X X X X X X

Legend: o = set but no catch; X = not set; - no information. 'For traps not set after 1966. More recent settings may have occurred for some. b Porto Paglia and Porto Scuso combined

C Porto Paglia, Porto Scuso and Isola Piana combined.

d 9,018 is average for Favignana and Formica combined.

Sources: Pavesi (1889), Hamre et a1. (1966), Alonc1e et al. (1971a), Instituto Centrale di Statistic a (1972, 1974), P. Arena (personal communications), R. Sara (personal communications).Data are often inconsistent; some mean values have been used. Table 12. Pavesi's (1889) classification of Italian traps. with very small tuna weighing 25-30 kg. The season ended about June 10 Order Number of Tuna per Year Number of Traps rather than at the usual date, about June 24-25. The figures for this year First 5,000 or more, sometimes 10,000 7 (M iyake 1976) indicated the first real improvement in the stocksince 1970. Second 2,000 or more, sometimes 5,000 3 The size of the catch had increased; Third 1,000 or more, sometimes 3,000-4,000 6 for the second time, and the average Fourth 500, not exceeding 1,500 11 weight of the fish had decreased sig- Fifth Rarely exceeding 500 12 nificantly for the first time, since 1973. Table 13. Catches for the Sicilian and Sardinian traps for 1970-1975, as reported Samples of the Sicilian trap by Miyake (1976) and P. Arena (personal communication). catches in 1958 and 1965-1971 (Fig- ure 57) suggest that giant fish were Year Traps Fish Tons Fish Tons Average most important in all but two years, (xl000) (xl 000) per Trap per Trap Weight (kg) constituting from 35 to 100 percent of the individual samples. The medium fish, or golfitani, made up the' 1970 ? 3.3 0.7 205 majority of the catch in two years, 1971 ? 3.9 0.7 191 and contributed from 0 to 65 percent 1972 9 3.3 0.7 364 74.1 204 of the respective samples. Small fish were apparently insignificant in the 1973 7 1.4 0.3 193 45.3 234 catches, never exceeding 2 percent 1974 5 2.6 0.7 522 141 270 of a sample. The golfitani were most 1975 6 3.7 0.7 624 119 190 important in 1958 and 1967, and were 1976 4 3.2 0.6 793 161 203 less so from 1968 on. The 13 available samples of in- Table 14. Maximum, minimum, and average weights per Italian compartment dividual catches of Sicilian traps which contained important tuna traps for 1971-1957. (Aloncle et a!. 1974, Miyake 1976) provide striking evidence of the ten- Annual Average Weight (kg) dency of the bluefin to school by Compartment Area Location Minimum Maximum Average size. Six samples consisted entirely of medium fish, 122-185 cm long, and six consisted entirely of giants, Trapani Sicily (W) 106 178 140 over 195'cm long. Only one con- Palermo Sicily (NW) 71 184 121 tained a mixture of the two groups, Messina Sicily (NE) 33 160 104 including fish from 147 to 233 cm long. The spreads between the mini- Siracusa Sicily (E) 20 174 114 mum and maximum lengths ranged Agrigento Sicily (SW) 66 133 101 from 28 to 39 cm, with an average of Cagliari Sardinia (SW) 67 115 93 33 cm, in the samples of medium Sassari Sardinia (N) 75 181 126 fish, and from 34 to 52 cm, with an Catanzaro Mainland (SW) 16 78 46 average of 46 cm, in those of large fish. The 1958 sample (Figure 57) consisted of two catches, taken two days apart. One consisted entirely of golfitani which had appeared in good consisted of enormous fish, includ- giant fish, and the other entirely of numbers in 1967-1968 had been prac- ing one "matanza" (removal of fish medium fish. The same situation ex- tically annihilated by 1972, and that from the trap) of 111 fish whose av- isted for samples of two different the typical mean weight ofthe catches erage weight was 470 kg! The catches catches taken in a single trap on the had consequently increased from at the end of the season, on the other same day in June 1965. This ten- about 150 kg in 1967-1968 to about hand, were mainly of fish weighing dency to school by size indicates that 270 kg in 1972. He characterized the about 80 kg. Despite this recruitmeht size data must be collected on a more 1972 fishery as depending on "the of smaller fish, however, the annual continuous basis than has been pos~ remnants of ancient year classes, with catch had still declined drastically sible in the Italian fishery to permit no possibility of compensating for and the average weight of the fish accurate estimates of the composi- their loss with the younger classes caught had increased remarkably tion of the annual landings. which should have constituted the (Table 10). Sara (personal commu- The use of purse seines for blue- strength of the catches." Sara (per- nication) advised us that the 1975 fin tuna was introduced into the Ital- sonal communication) also informed catches consisted of large fish up to ian waters of the Tyrrhenian and us that the early landings in 1973 June 7-8, after which they continued

58 Adriatic Seas in 1950 (Scaccini and Miyake (1976) stated that the season ment to the spawning stock of large Biancalana 1959). These authors in- started in May and peaked in June- bluefin. dicated that the early fishing occurred July. He indicated that the fishing Although Ninni (1921a) and mainly along the Tyrrhenian coast area was in the southwestern Scordia (1939) had reported occur- from Salerno to Gaeta and along Tyrrhenian Sea, from the north coast rences of bluefin tuna off the Italian much of the Adriatic coast between of Sicily to Salerno. Data for the Adriatic coast near Venice and near Barletta and Trieste. They reported catches in 1972-1976 are shown in Manfredonia and Molfetta, respec- that the season extended from the Table 15. P. Arena also furnished tively, it was not until 1950 that an end of March to mid-November, and data (Miyake 1976) on the size com- Italian Adriatic tuna fishery was ini- that the bluefin tuna taken weighed position of the catches, as shown in tiated (Scaccini and Biancalana from 4 to 30 kg. Their statistics Table 16. 1959). This purse seine fishery has showed that the total Italian purse The seine catch in 1975 thus ap- been described by Levi (1977). The seine catches from 1950 through 1957 proached that of the traps in their season extended from the end of ranged from 351 to 722 tons per year, better years early in this century. it is March to mid-November, and the amounting to from 23 to 72 percent uncertain whether the concentration fishing area covered most of the coast of the corresponding catches of the of large tuna in offshore waters is a between Barletta and Trieste (Fig- traditional trap fishery. new phenomenon, or one which sim- ure 58). The most successful fishing Purse seines, including a modi- ply had not previously been observed occured in March-April off Pescara fied type called the cianciolo (de and used. The decline of the trap and Punta Penna, in the central Gaetani 1948) have also been used catches encouraged the exploration Adriatic, for fish between 10 and 50 extensively to catch small fishes, in- of offshore waters, and the use of kg and in August-October, to the cluding young b1uefin tuna, in Sicil- active gears. The development of the north, off Porto Garibaldi and ian waters. This seining often takes modem purse seine and longline pro- Cattolica-Cesenatico for 6 to 10 kg place at night, with the aid of a light vided the necessary equipment. It had fish. The fishing originally took place to attract the fish. Despite the regula- been generally agreed that the blue- about 15 miles (24 km) or less from tion prohibiting the capture of b1ue- fin move offshore from the area of the coast, but this distance has gradu- fin tuna less than 90 cm long (Sara the traps to spawn (see Section VI), ally increased to 30-40 miles (48-64 1968), great numbers of bluefin less and the use of pelagic gears to in- km). The yearly catches have varied than a year old (55 cm long) have crease the catch had been advocated between 83 and 434 tons, with an been caught (Sara 1965c, 1968; de many years ago (Scordia 1942). average of 186 tons, from 1955 Cristofaro 1970, P. Arena, personal The average weight and size through 1971. Levi (1977) reported communication). Sara (1973) attrib- composition data provided by Arena that two of the larger and more mod- uted the decline in the numbers of confirm the indications, also noted in em Italian seiners had entered the large bluefin to the heavy fishing of the average weights of the trap Adriatic fishery in 1976. P. Arena young individuals. catches, that there was a substantial (personal communication) advised us The French seiners which began recruitment of younger fish to the that the 1976 Italian seine catch in fishing small blue fin and albacore in central Mediterranean spawning stock the Adriatic had reached about 1,000 the Ligurian Sea (see subsection a) in 1975. The size composition data tons in October. in 1967 were soon joined by their suggests a strong influx of fish in the Hook and line fisheries have ex- Italian counterparts (Cesareo 1973, 40 to 100 kg class in that year. This is isted in several parts of the central 1974a). According to Cesareo, these most encouraging, but whether the Mediterranean, but the most impor- vessels had reduced the stock to such stock can withstand the massive im- tant was in the Strait of Messina. an extent by 1970 that there was no pact of the new seine fishery remains Scordia (1931, J 932, 1934, 1935) and incentive to fish in the area for the to be seen. Genovese (1965) have described this next two years. The stock apparently As noted above, Paini (1975) re- fishery, which embraced two distinct recovered, or returned to the area, in ported that the large seiners, after seasons. The fall-winter fishery (Sep- 1973 and the seiners were present in completing their fishing in the tember-March) occurred in the north- 1974. Tyrrhenian Sea and the Sicilian Chan- ern part of the Strait of Messina, and A most important innovation in nel, moved north to fish small tuna took small or medium sized fish be- the central Mediterranean tuna fish- and albacore. P. Arena (personal tween spawning seasons. The sum- ery was the creation of a fleet of communication) advised us that sein- mer (late June-August) fishery oc- modem italian seiners which began ers had taken about 2,600 tons of curred in the southern part of the fishing for large spawning and bluefin weighing from 10 to 100 kg Strait, and took giant fish which were postspawning bluefin in 1972 (Paini in the northern Tyrrhenian and maturing or recently spent. Scordia 1975, Miyake 1976). According to Ligurian Seas in September and Oc- believed that the winter fish came Paini, these vessels fished for two tober 1976. Thus very heavy pres- from the Tyrrhenian Sea, and the months off the Aeolian Islands and sure is also being put on the stock of summer ones from the Ionian. She for one month in the Sicilian Chan- young fish just as it appeared to be provided extensive data on the nel. Afterward, they went north and furnishing urgently needed recruit- catches for 1928-1935. Genovese pre- fished for small tuna and albacore. sented the size composition, by

59 30

1969 20 '.5. iO l

20 1965

~ 30 ~ ~ 1966 t:\ 20 ~ 10 It + 30 l

20 1970 ~67 10 l

+ +

30.

1971 20 ~O. 10 L

50 100 150 200 250 300 30 LENGTH (em) 20 l,.0. 10

+ 50 100 150 200 250 300 LENGTH (em)

Figure 57. Lengths of bluetill tuna taken in the Sicilian trap catches in 1958 and 1965-1971 ("+" on graph means less than 0.5%). weight groups and months, of the The sex ratios of the tuna taken longliners fished primarily for catches for most of 1948-1950 and in these years showed a very slight broadbill swordtish, but caught blue- 1953-1954, with the sex ratios for predominance offemales (about 52% tin tuna incidentally (Sara and Arena some samples. The bluefin taken in females), which did not vary greatly 1967). Their tuna catches have not the winter fishery were mostly in the between months and years. Arena been recorded in the statistics. R. Sara medium size group, but with many (1959a) described a productive line (personal cOlumunication) estinlated small tish and a few giants. The in- tishery off the Aeolian Islands (n0l1h that the swordtish longliners might troduction of live-bait chumming in of eastem Sicily). Up to 27 tish were have captured "not over 500" tuna 1950 increased the catch from a few taken per boat day under favorable with an average weight of about 150 hundred tish per year to as many as conditions. It was necessary to use kg during the 1972 season. Sara and 1,500 in a month, but after 1953 the tine lines baited with sand launces, Arena (1967) noted that smaller catch declined. The summer catches Ammodytes cicirella. The tish taken longlines used primarily for dolphin were nearly all giant fish, with a few generally ranged from 30 to 40 kg. (fish), Coryphaena hippurus mediums. Only from 23 to 44 tish Much larger individuals, 200 kg and Linnaeus (1758), also took per year were taken in 1948-1950, over, were often hooked, but usually unrecorded numbers of small blue- and none were caught in 1953-1954. broke the light lines. The Italian fin.

60 The Japanese longline fishery en- Table 15. Catch data for the Italian purse seine fishery in the southeastern tered the Mediterranean in 1972, tak- Tyrrhenian Sea and the Sicilian Channel (Miyake 1976, P. Arena, personal ing 459 bluefin between 100E longi- communication). tude and 200E longitude. Its catches in this area increased to 748 fish in Year Boats Fish Tons Average 1973 and 4,914 in 1974 (Fisheries Weight (kg) Agency ofJapan 1973, 1974, 1975). Assuming that the weight of these fish was the same as the average for 1972 8 9,000 2,300 256 the entire Mediterranean, the cor- 1973 11 8,500 2,200 259 responding tonnages would be about 1974 15 ·13,000 3,500 269 74 in 1972, 156 in 1973, and 835 in 1975 16 32,000 5,800 181 1974. The numbers of fish taken in 1975 are not available, but the total 1976 4,120 Japanese Mediterranean catch declined from 2,192 tons in 1974 to tioned in this report. Cesareo (1974b) On the other hand fish of the same 1,100 tons in 1975, because of con- stated that there had always been gi- size were found from one half to five servation measures (Kume 1976). ant bluefin along the Italian Adriatic miles off the coast in very shallow The largest catches were taken south 0 coast from the delta of the Po south- water in the middle Adriatic between of latitude 40 N in May and June, ward, from Punta Pila to Porto Corsini San Benedetto de Tronto and the corresponding to the "arrival" run of (Figure 58). They were especially Gargano promontory. They also oc- maturing bluefin in the area. Catch numerous in 1968-1970. Catches curred in the mid- Adriatic, always rates, in fish per thousand hooks, var- were scarce, however, because of the on the surface, north of the island of ied from 0 to 12.8 in May, 7.8 to 14.6 lack of sport fishing effort. Cesareo's Pianosa over the trench of Pomo. in June, and 0 to 19.5 in July. Thus comments were in response to a let- Bluefin of 30-70 kg and more than a the most consistent catch rates were ter from a sportsman who reported meter long, rare in the western obtained in June, during the arrival the capture of a giant fish weighing Adriatic, were caught habitually in run when the maturing bluefin are 176 kg off Punta Pila in 1974, and the eastern Adriatic, and in summer believed to be reluctant to feed (see recalled taking one weighing 152 kg and early fall north of the mouths of Section VI). The highest catch rates, in the same area in 1971. the Po near Venice. Scaccini showed 14.6 and 19.5 fish per thousand Scaccini (1961) discussed the that this apparently strange pattern hooks were obtained in the Ionian distribution of young blue fin tuna in was based on currents whose waters Sea in' June and July, respectively. the Adriatic in relation to physical, were more favorable than the sur- Sport fishing for small bluefin chemical and dynamic conditions of rounding ones for the tuna of the tuna and albacore (Thunnus a/a/unga) the environment (Figure 58). Very sizes in question. in the Ligurian Sea was initiated by small fish (11-20 cm, 40-100 g) oc- The oldest bluefin tuna fishery French and Italian anglers in 1962 curred in summer close to the coast in the Adriatic is by traps situated and 1963. This fishery was very suc- from north ofRimini to Ancona over along the northern coasts of Yugo- cessful in the years 1964-1968, with sandy bottom. Fish 40-60 cm long slavia and the adjacent islands. As daily catches in 1964 averaging 30 (3-5 kg) and larger ones 10-12 kg elsewhere in the Mediterranean, the tunas a day for a well crewed boat and up to 1 m long were fished by number of traps fishing offYugosla- with expert anglers. This average de- seine from April to September in the via has decreased greatly. Whereas clined to 0 in 1971, reportedly be- north Adriatic from the mouths of Paron a (1919) listed 38 active em- cause of heavy fishing by Sicilian the Po to just north of Ancona, al- placements, only 21 existed in 1957 and French seiners in 1968-1971. ways from 6-7 to 12 miles offshore. and 17 in 1958-1959 (Belloc 1961). Some improvement in the fishing was noted in 1972 and 1973, after the seiners had left the area. The schools were much less numerous than before the seining, however, and Table 16. Size data for catches ofthe Italian purse seine fishery in the southeastern were present for a much smaller por- Tyrrhenian Sea (P. Arena, personal communication). tion of the year (Cesareo 1973, "A.C." personal communication). This im- Percentage of Percentage of provement has evidently continued; Size Range (kg) 1974 Catch 1975 Catch nine boats took 680 kg of blue fin and albacore in a day and a half in a 40-100 kg 30% tournament off San Remo, Italy, in September 1975 (di Sant' Ignazio 100-200 kg 20% 25% 1975). Friction between seiners and 200-300 kg 50% 35% recreational fishermen was also men- 300-500 kg 30% 10%

1937, 1938) data for individual Tu- occurred between May 29 and June upper limit of salinity for large "ar- nisian traps showed that those on the 23 (Anonymous I928a, 1929a, 1932). rival" (maturing) bluefin. He added north coast (Cap Zebib, Sidi Daoud, BelIoc (196 I) reported that the fish- that, had he known what he then did Ras el Ahmar and El Aouaria) caught ing began at the end of May, peaked about the sensitivity of maturing blue- larger fish than those on the east coast in the first half of July and ended fin to salinity, he would not have (Monastir, Kuriat, Conigliera, and during the last half of July. Sara attempted to establish a trap east of Bordj Kadidja). Yearly average (1964) stated that the Libyan traps EI Mongar (in water of higher salin- weights for the western traps varied fished about 15 days later than those ity) near Tobruk. from 42 to 246 kg, whereas those for of Sicily, Sardinia and Tunisia. In the east coast traps ranged from 47 to 1964, the fishery extended from the c. Eastern Mediterranean and 62 kg. Postel's (1956) data for 1955 22nd to the 26th week (about May Black Sea Bluefin tuna are extensively dis- catches showed the same trend: 125 25-June 23) (Hamre et al. 1966). tributed over the eastern Mediterra- and 115 kg for Sidi Daoud and EI The only size sample available nean (Figure 52), except its south- Aouaria, respectively, and 52 kg for for the Libyan fishery is for the 1964 east corner, but the only fisheries of Kuriat. catches (Figure 60). About three- any importance are those of Greece Sella (1912a) reported that there quarters of the fish were in the "me- and Turkey. Annual catches reported were quantities of blue fin tuna along dium" category, with the remainder for Greece since 1952 have ranged the Libyan coast, and the installation in the "large" group. from less than a ton to 1,220 tons, of traps began in 1914 (Parona 1919, Except for an ephemeral attempt and those for Turkey since 1957 from Ninni 192Ib). Data are available for near Tobruk (Sella I932a), the east- less than a ton to over 1,500 tons. the catches in Tripolitania (western ernmost tuna trap which fished Catches in Greece since 1968 and in Libya) in 1915, 1919-1936, 1939, spawning bluefin in the Mediterra- Turkey since 1970 have been negli- 1951, 1955, 1959, 1972, and 1973, nean was at EI Mongar near Bengasi gible (Hamre et al. 1966, Miyake and but not alI on a comparable basis. in Cyrenaica, Libya. Information on Manning 1975, Miyake and Tibbo The most complete data are for 1921- this trap is meager. In 1924-27, it 1972). 34 (Anonymous 1928a, 1929a, took from 1,039 to 3,286 bluefin tuna Eleven traps were active in 1932a, 1934a, 1934b, 1935a, 1935b, per year (Anonymous 1928b). The Greece in the period 1954-1958 1936). In 1915 and 1919-20 from latter figure, attained in 1927, was (BelIoc 1961). The maximum annual one to three traps were set each year, reportedly the highest for any trap in catch (all species) per trap was 21 and annual catches ranged from 1,160 the Mediterranean in that year. In tons; few catches exceeded 10 tons to 6,206 fish per trap. In 1921-34, 1928, only 197 tuna were taken and many were less than one ton. AII from six to 13 traps were set each (Anonymous 1929b). Catches offrom of the traps were located on the year, and annual catches varied from 112 to 436 tuna per year are Iisted for Aegean (eastern) coast of Greece 285 to 1,200 tons per year, consist- Bengasi or Cyrenaica for 1930-33 (Figure 61), with all but two on the ing of from 547 to 2,067 fish per trap (Anonymous 1932a, 1934a). Peleponnesus. Ninni (l922) quoted with average weights of from 56 to In 1927, the first and last b1uefin Vinciguerra (1896) to the effect that 110 kg per fish. In 1935, 1936 and catches at EI Mongar were on May the only bluefin tuna fisheries in the 1939 from seven to 10 traps fished 31 and July 18, respectively (Anony- Aegean were at Melina in the Gulf of each year and took from 1,133 to mous 1928b), and in 1928, on June Volos and Gialtra on the island of 1,737 fish per trap year. The average 26 and July 14 (Anonymous 1929b). Euboea. Ninni concluded that in weight of the fish caught in 1936 was The latter season was regarded as spring bluefin tuna migrated north- 75 kg. Catches totalled 1,120 tons in unusually late in starting. ward in two groups through the 1951 (Anonymous 1952),6,403 fish No quantitative data are avail- Aegean from a wintering area around averaging 86 kg in 1955 (Postel able on the sizes of the fish taken, but Crete. The major group skirted the 1962), and 1,950 tons in 1959 SelIa (1932a) stated that they were coasts of Asia Minor and the adja- (Anonymous 1960). Recent landings small or medium size, and that their cent islands and a smaller one tra- have been considerably smalIer, with gonads were ripe. Anonymous versed the channel between Euboea four traps taking 1,550 fish in 1972, (1929b) reported that the tuna caught and the mainland to enter the Gulf of and three taking 2,360 in 1973 (R. in 1928 were very small. Volos. Athanassopoulos (1923, 1924, Sara, personal communication). The Because of the irregularity of its 1926) considered the bluefin to be a total yearly bluefin tuna catches of catches and the small size of the fish rare fish in Grecian waters, particu- Libya for 1964-1974 varied between taken, Sella (1932a) did not regard larly off its western (Ionian ,Sea) 300 and 2,000 tons (Miyake et al. EI Mongar as a true "arrival" trap. coast. Oren et al. (1959) reported 1976), with the largest catches oc- Since it did not catch large spent fish, trolling catches ofvery small (45-53 curring in 1968 and 1969. he also felt that it did not qualify as a cm total length) bluefin tuna in sev- The Tripolitanian traps fished the "return" trap. It appears to have been "arrival" run only, although evidence abandoned soon after this information eral parts of the Aegean during an of a potential "return" fishery has was published. He pointed out that exploratory fishing cruise Septem- ber-December 1952. been noted (Anonymous 1932). First this trap was east of the 38 0/00 catches for 1927, 1928, and 1931 isohaline, which he regarded as the

63 15- 15

o o 1860 65 70 75 80 90 95 1900 15 15

10 10

0 0 190t 05 10 15 20 25 35 10 10

o NUMBER OF FISH/103 5 5 • METRIC TONS/102

o o 1941 45 50 55 60 65 75 80 Year

Figure 59. Annual catch of bluefin tuna fl"Omthe Sidi Daoud trap in Ttmisia in thousands or fish cmdhundreds of metric tons.

Turkish tishing for bluetin tuna Parona (1919) showed 26 loca- but lyigOngor (1957) said that the is by trap, handline and harpoon tions for traps in the easklll Sea of traps tished from early April to the (Ninni 1922, Devedjian 1926, Marmora and the l3osphorus. BeHoc end of August. He estimated the av- HovllSse 1929, Lebedetf 1936. Akyiiz (1961) noted that Devedjian (1926) t.:rage season's catch per trap at 100- and Artiiz 1957, Iyiglingiir 1957. showed 225 emplacements for Turk- ISO tuna. Opinions also differed as Belloc 1961). Lebedeff (1936) de- ish traps in the l3Iack Sea, Bosphorus, to the periods of passage. Ninni described sport tishing near Istanbul in Marmora and Dardandlcs. but his scribed an "arrival" (northward) run the winter of 1935-36. The favorab Ie charts show only 19 in the Bosphorus from late March to mid-August and a situation for developing a sport tish- and eastern Marmora and two in the "rdurn" (soulhward run from early ery there was also mentioned by Dardlmelles. Only a few ofthese wen.: August 10 December or even Febru- Iyigiingor (I957), but we have no noted for catching bluetin tuna. Ninni ary. I-Iovasse (1927). on the basis of further information on this subject. (1922) noted that there were some ca1\.:hn.:cords for the years 1915 and "summer" and some "winter" traps, 1921-1

Figure 60. Length composition of samples of blue fin tuna taken along the Libyan coast in 1964 ("+" on graph means I~ss than 0.5%). the landings: one with maturing fish The hook-and-line fishing seasons are ones stayed near prince's Island. Dur-: in February, March and April, one November-January and March-April; ing a few days of sport fisi:1ing;from with spent fish in July and August, the fish do not take bait July-October December 25, 1935 to late March and a lesser one in December. (lyigilngor, 1957). Both of these fish- 1936, Lebedeff caught tuna of 120, Hovasse believed that the first run eries are centered around Istanbul. 230, 350, 380 and 400 kg. He also was an "arrival" migration into the Ninni (1922) concluded that the lost several large bluefm wi:1ichbr,oke Black Sea, where spawning took quantity of blue fin tuna available was his lines or leaders. One of these;"'j place and the second was a "return" much greater than was indicated by which was later caught in a net and run from the Black Sea. He did not the catches of the traps, since the identified by the hook and leader understand the significance of the latter did not extend into sufficiently which had remained attached to it, third maximum. lyigUngor (1957) deep water to fish tuna effectively, weighed 450 kg. listed three rather similar runs: and also were too weak structurally Hovasse (I 927) noted that blue- March-April, July-autumn, and No- to hold any considerable quantity of fin tuna occurred in the Aegean Sea- vember-January. AkyUz and ArtUz bluefin. He noted that a trial setting Marmara-Black Sea area in waters of (1957) specify an "arrival" run simi- of an Italian style trap at Touz extremely different salinities, from lar to Ninni's, from April to early Burnum in 1913 had not produced 18.3 0/00 in the Black Sea to 39 0/00 August, and a "return" run from late satisfactory results, but did not con- in the southern Aegean. In the vicin- October into December. These au- sider this experiment conclusive. ity of Istanbul tuna are found simul- thors show the average volume of Evidently most of the bluefin taneously in deep waters with salin- bluefin tuna sales in the Istanbul mar- taken near Istanbu I are large. Most of ity of 38 0/00 and shallow waters ket, by month, for 1935-1955. These the fish examined by Akytiz and with only 17 0/00 to 18 0/00. He show a maximum in March and an- Arttiz (1957) at the Istanbul market stated that tuna in the area were found other in July, with good volume in (1955-1956) were in the 170-280cm in considerable ranges of tempera- April, February, and August and a range, with the smallest 120 cm and ture-as low as 14°C to 19°t, ac- minimum in June. The yearly vol- the largest 330 cm. Samples exam- cording to depth-in the Black Sea ume of bluefin tuna sales in the ined there in 1967 and 1968 (Hamre at the time of the "arrival." These Istanbul mwket varied from 85 to et al. 1971) ranged from 85 to 320 findings conflicted with Roule's 537 tons in 1909-1916 (Ninni 1922), cm, with most of the fish from 155- (I 924) hypothesis of a stenothermic from 15 to 112 tons in 1928-1938 290 cm (Figure 62). Lebedeff(1936) and stenohaline tuna. and from 40 to 764 tons in 1953- mentions that hook andlin~ catches Small bluefin tuna range along 1955 (AkyUz and Artilz 1957) The in 1936 included 40 bluetin over 400 the Mediterranean coasts of Turkey allocation of catch by gears is not kg, 10 over 600 kg, and some from and Syria, and occasionally occur off shown. 700 to 775 kg. He noted that fish Cyprus (Carp 195 I, Oren et al. 1959, Harpooning is practiced both over 200 kg were taken only in the Sara 1964). Carp reported a Turkish from the shore and from small boats fast current, whereas 100 yards away fishery for bluefin (apparently 10-30 (Devedjian 1926). Handlining is also only individuals of 20-50 kg were kg) along the Anatolian coast and in practiced from small boats caught. In early April, the large and the GulfofMersin. Oren et al.(1959) (Devedjian 1926, IyigUngor 1957). small bluefin left, but medium sized reported captures of very small {45-

65 53 em) individuals in various localities in the northeastern corner of the Mediterranean in November and De- cember. They also noted catches of young tuna off Haifa, Israel, in waters with salinities of 39.58 0/00 or more. Sara (1964, Figure 1) indicated that the northeastern comer of the Mediterranean (Haifa, Israel, to the •• TURKEY Gulf of Mersin, and around eastern (UATOLlA) Cyprus) is a year-around habitat of ~IA MINOR) 5-25 kg bluefin and an August-No- vember habitatofO.2-3 kg bluefin. .~ The southeastern corner of the Mediterranean (coasts of Egypt and 0 :-\, ~ e .~ southern Israel is evidently devoid of o . ,00. bluefin tuna. The stranding ofa single ~ .pP bluefin near Alexandria (Heldt! 937) Q tt! .•,\:I" 0'" was regarded as an extraordinary ~C1TIES • ,. e_II_A&. IIEFERENcn event. N': I,PILO_nUS "DARDANELLES a.A_ %UA OF d. Summary. a.n¥OIA MAllIiAlIA ,~ •• YIAD'RA '.IITANRUL Sara (1964, 1973) summarized "PRINCES IS. '.GULF OF the distribution of bluefin tuna in the 10.ROS~RUS ~ WI"" Mediterranean Sea. From August through November, almost all of the u· 24" 20;' 2it 30 2" Mediterranean is filled with large schools of very young tuna born in Figure 61. Geographic references in the Aegean Sea area. the year. After November, when they have attained a weight of about 2 kg, few are taken, probably because of bad weather rather than because of their absence. With the return of good weather in late winter, they are found in practically the same places, weighing 4-5 kg. Theseyoung tuna remain in the areas where they were born, making small movements in response to changes in environmental condi- 30 tions, and in search of food, until they reach sexual maturity. Sara's 20 1967 (1964) distribution chart indicates 'u scattered concentrations of bluefin ~ 10 weighing 5-25 kg near most of the ~ islands and coasts in the western and ~ 0 central Mediterranean, except the Af- ~ 30 rican coast between Morocco and Tu- nisia. In the eastern Mediterranean, concentrations are shown in the - 20 1968 Aegean Sea, around the Bosphorus, 10 and off the northeastern coasts. Medium-sized tuna (30-100 kg) ++ are found off many of the coasts o •• . I 50 100 150 200 250 300 throughout the year. Sara's (1964) LENGTH (em). chart locates these fish along the Af- rican coast from Gibraltar to Bengasi (mainly from Tunisia to Cape Misunita), along the Spanish and French coasts and around the Balearic Figure 62. Length composition of samples of bluefin tuna taken in Turkey in Islands, in the central, eastern and 1967 and 1968 ("+" on graph means less than 0.5%). southern Tyrrhenian Sea, along the

66 east coast of Sicily and around the Other occurrences are shown near The fisheries for large bluefin islands in the Sicilian Channel, in the Gibraltar, in the Gulf of Lion, in the were historically the most important Adriatic Sea and in the northwestern Bosphorus, and off Bengasi. Sara in the Mediterranean, and laws pro- Aegean Sea. Sara (1973) said that (loc. cit.) believed that the major oc- hibited the capture of young fish in these fish are especially visible in currence oflarge bluefin in the Medi- Italian waters more than a century late summer and autumn, when they terranean is the spawning run from ago. Catches of young bluefin have chase prey relentlessly on the surface thelbero-Moroccan Bay, whose vol- increased since 1920,. and this ten- near the coasts. ume and movements are greatly in- dency has accelerated after World Large tuna (over 150 kg) are fluenced by the inflowing Atlantic War II. Perhaps in consequence of abundant. except in certain local ar- Current. Occurrences in other sea- this, the landings of large bluefin by eas, only from April to September sons consist of relatively small num- the traditional trap method declined, (Sara 1964, 1973). The principal ar- bers offish which stay in areas where especially in the 1970s. The intro- eas of abundance indicated in Sara's food is plentiful, such as the Gulf of duction of longline and purse seine (1964) chart are off western Sardinia, Lion (off the mouth of the Rhone), fisheries for large bluefin in this pe- Sicily, Tunisia and. western Libya. the Tuscan Archipelago, the Aeolian riod, however, had restored the Islands, the Strait of Messina and the catches of large fish to their earlier Dardanelles. level by 1974.

67 v. SPAWNING

A. INTRODUCTION gonads. This index istherefore inversely used to determine the spawning sea- Considering the amount of re- proportional to the maturity of the fish. sons and areas of the bluefin tuna. The search which has been devoted to the Other indices are defined where they presence offully ripe adults is assumed Atlantic bluefm tuna, positive informa- first occur in the text. to indicate spawning. tion on its spawning habits is surpris- Stages of maturity have been ingly incomplete. The earliestand most evaluated by several methods, some C. CRITERIA FOR extensive information on this subject is subjective and some objective. The ap- DETERMINING SEASONS from the Mediterranean, but even there pearance and physical characteristics much remains to be learned. The situa- AND AREAS OF SPAWNING, of the ovaries and the ovarian eggs are tion is far worse in the important east- AND THEIR LIMITATIONS among the subjective criteria used for ern North Atlantic region, since, to our this purpose. Visual diagnosis may be knowledge, no larvae or small (less 1. Presence of Ripe Adults based on the color of the ovaries and than 12 cm) juveniles have been col- The evaluation of the condition, the extent and color of their external lected in any of its areas which have or degree of maturity, oflhe gonads of veining. Their consistency (hardness been assumed to be spawning grounds. adult fish is one of lwo approaches or softness) and their size and shape are Greater advances have been made in the western North Atlantic, but positive information there is limited to relatively small areas. Aside from a few larvae collected near the Equator, we found no information whatsoever on the spawning of the species in the South Atlantic. The paucity of knowledge concerning this vitally important phase of the life of the bluefin tuna may be attributed to the serious limitations in- herent in the methods used to obtain . ,., this information . - --;- --;.>,:-<:::-:

1.1 ••• ilL B. DEFINITIONS Larva: Matsumoto et al. (1972) stated that the larval stage of nearly all tuna species ends when the larva has attained 10 to 13 mm standard length (SL) (Figure 63). We have arbitrarily selected 12 mm SL as the size at which the bluefin tuna passes from the larval to the juvenile stage. Juvenile: Postlarval fish may be regarded as juveniles until they reach maturity-- a considerable size, in the case of the bluefm tuna. In this section on the spawning of this species, however, we have arbitrarily limited the term 'Juvenile" to include individuals from 12 to 120 mm. Bluefin tuna only slightly larger than 120 mm are active predators and are taken in some fisheries. '.111I11I 8L Index of Maturity: The numeri- cal index of maturity most frequently used in this section is the weight of the Figure 63. Early life history stages of Thunnlls thynnus of the western central entire fish divided by the weight of the Atlantic (Richards 1989).

6X important physical factors. The size and Maturing and post-spawning fish veniles are collected, however, requires consistency of the ovarian eggs, and may have the same indices as the size knowledge of their growth rate, and the tenacity of their adhesion to one of their gonads increases and then de- also of the currents in the collecting another and to the walls of the ovaries creases. Also, maturing fish are con- area. also provide indications of maturity. siderably heavier than spent ones of the Although this approach is very The more objective criteria include same length. This fact introduces er- logical, its execution has not proved to indices of maturity, usually expressed rors when indices for fish in these dif- be easy. The collection. and identifica- as a relationship between the weight of ferent phases are compared. In addition of eggs and larvae is difficult. Blue- the ovaries and some measurement of tion, the testes of males decrease in size fin eggs cannot be positively identified the fish from which they were taken. much more than the ovaries of the fe- unless they are hatched and the larvae Examination of histological sections of males after spawning has been com- are reared to an identifiable size gonads permits more exact assessment pleted. Thus comparison of indices for (Piccinetti and Piccinetti Manfrin 1970), of stages of maturity, but few such fish of different sexes may be mislead- which is a most difficult process. The studies on bluefm tuna have been pub- ing. Frade (1937) pointed out these identification of larvae has been cop.- lished. sources of error and used corrections troversial (Sella 1924, Dieuzeide 1951, Estimates of spawning areas and for the differences in gotiad weight be- Duclerc et al. 1973, Richards 1976). seasons from gonad condition are sub- tween sexes and in total weight be- Sella and Richards questioned ject to many limitations. Unless the tween maturing and spent individuals Ehrenbaum's (1924) tentative identifi- specimen is fully ripe, serious errors of the same length. These refinements cations of "Orcynus thynnus L.", and may be involved, as these fish can travel in the method, however, have appar- Richards reidentified several of great distances in short periods (Mather ently been ignored. We have observed Ehrenbaum's larvae of tunas and tuna- 1962, 1969). Also, fully ripe bluefm another possible source of error in indi- like species. Duclerc et al. (1973) found tuna are difficult to catch on hook and ces of maturity for bluefin tuna in the it impossible to distinguish eggs and line as they are reportedly reluctant western North Atlantic. When large larvae of "Thunnus thynnus L.", from Sara to feed (Sella 1929a, Rivas 1954, bluefin tuna arrive in New England those of"Auxis thazard', even after the Sara 1964, 1973). Their capture in traps waters in July (Section IV), they are eggs had been hatched and the larvae is extremely rare. Sanzo (191 Oa)found spent and their gonads are small. To- reared to lengths of 5.0 mm. Duclerc et a ripe female in a trap near Palermo, ward the end oftheir feeding season, in al. (1973) and Richards (1976) ques- Sicily, in 1908, but had not encoun- late summer and early fall, their go- tioned Sanzo's (1932) descriptions of tered another when he produced his nads become almost completely en- the egg and larval stages of "Orcynus final (1932) work on the eggs and lar- cased in adipose tissue. If this tissue is thynnus Ltkn.", and felt that they should vae of the b1uefm. Likewise Rodriguez- not removed before weighing the go- be verified. Some encouraging progress Roda(1964a, 1967a) had observed only nads, the maturity index may be almost has been made recently, however. one ripe female in his extensive studies as high as for a ripe fish, even though Duclerc et al. (1973) and Scaccini et al. at Barbate, the most productive tuna the gonad proper is small and dormant. (1975) have reared larval bluefm tuna trap in this century, and other sites. He Baglin (1976) noted that the average for periods of up to eight days from remarked that the oviduct of this indi- weight of the adipose tissue attached to eggs collected at sea. Richards and vidual might have been obstructed. The the ovaries of six giant bluefin taken Potthoff (1974) have produced a most recently developed purse seine fishery off New England in August 1975, was thorough description of larval bluefm in the central Mediterranean spawning 1,152 g, while the average weight of tuna more than 3.0 mm (SL) long. grounds (Section IV) has made more the gonads themselves was 1,114 g. The accuracy of estimates of mature bluefm available (R. Sara, per- The well documented presence of spawning seasons and areas based on sonal communication), but no studies fully ripe fish may therefore be a good the collection data for young stages, based on these catches have appeared. indication of a spawning area, but con- their length and growth rates, and cur- B1uefm tuna spawn fractionally, clusions based on nearly ripe fish may rent systems in the collecting area, de- by several separate emissions of eggs be very misleading. clines rapidly with the passage of time over a period of several days, rather from the hatching of the specimen. Not than by a single emission (Sanzo 1910a, 2. Presence of Pelagic Eggs and only does the error in calculating pas- Frade and Mana~as 1933). Thus, even Larvae sive transport increase, but juvenile when ripe fish are taken, the localities The times and locations of collec- bluefin tuna become active swimmers of capture may not indicate the tota!' tions of pelagic eggs and larvae form at a surprisingly early age. TIley attain area over which the fish have spawned. another basis for the determination, or their full complement of caudal rays at The fractional nature of their estimation, of the seasons and areas of about 16mm SL (Potthoff 1975). Sella spawning also adds to the difficulties spawning. When eggs or extremely (l929a) stated that the bluefin tuna in determining when bluefin tuna are small larvae can be identified, it may could already be considered an active fully ripe. As noted above, many ofthe be assumed that spawn ing occurred not fish at the age of 15 days. criteria used to determine stages of very long before the time of collection Most of the available data on the maturity are subjective. In addition, and not very far from the collecting growth of the early stages of the blue- even the seemingly objective indices locality. Estimating the time and place fin (Section Ill) have been presented in of maturity may be subject to error. of spawning when larger larvae or ju- terms of weight. Growth data in terms

69 year, but entered the Mediterranean in the spring, travelled along its northern ~ Major Known Spawning Areas shores to the Black Sea to spawn, then returned to the Atlantic, following the :.'~:Minor, Onevaluated or Hypothetical southern coasts of the Mediterranean, Spawning Area. in the summer. Scientific fmdings in the sixteenth and seventeenth centuries, however, raised questions about this theory and from 1875 to 1925 most authorities believed that spawning bluefin did not pass through the Strait of Gibralter in numbers. They felt that the Mediterranean bluefin tuna comprised an autochthonous population, which made only limited local movements to and from the spawning areas. Since 1925 evidence of migrations from the Atlantic into the Mediterranean has re- opened the question. A recent hypothesis (Sara 1964, 1973) satisfies many of the arguments used by both sides in this debate. Sara maintains that most of the large bluefm Figure 64. Bluefm spawning areas in the Mediterranean and Black Seas and the which spawned in the Mediterranean eastern Atlantic. were migrants from the Atlantic and spent the rest of the year in that ocean, but that most of the medium sized and of length would be much more useful studied and are better known in the small fish which spawned in the Medi- for back-calculating the localities where Mediterranean than elsewhere. terranean had been born in that sea and larvae or juveniles had probably been Bluefin tuna spawn over exten- had remained there until they attained spawned. sive areas of the Mediterranean and about 150 kg. These problems are dis- Collection data for eggs and small Black Seas (Figure 64). The larger in- cussed in detail in Sections IV and VI. larvae which have been reared to iden- dividuals, to which most ofthe research tifiable sizes furnish good indications has been devoted, spawn mainly in the b. Specific Occurrences of spawning dates and areas. Estimates last half of June and the first half of The first positive indication that based on collection data for larger lar- July. There is considerable evidence bluefin tuna spawned in the Mediterra- vae or juvenile stages, however, must that the smaller bluefin which have nean was presented by Cetti (1777) be regarded only as approximations. reached maturity (the older small blue- from observations made along the Unfortunately, most of the avail- fm and the medium-sized fish) spawn coasts of Sardinia. He found eggs, able data on the growth of early stages later, throughout July and into August, which he believed to be those of blue- of blue fin tuna (d' Amico 1816, Bourge and occasionally even into September. fin tuna, on the ropes of the traps, and 1908, Heldt 1930, Piccinetti and The principal known spawning ar- also in the water around the traps. He Piccinetti Manfrin 1970) were presented eas were in the southern central Mediter- also stated that the ovarian eggs offish in terms of weight (a characteristic ranean, around Sicily, off western taken in the traps in May were very which is seldom reported in this size Sardinia, and off northeastern Tunisia. well developed, but that those of fish range), rather than length. Length-age Additional reproduction has occurred taken in June had degenerated. He con- data for early stages ofbluefm tuna are around the Balearic Islands, off cluded tentatively that more large blue- needed to reduce the error in estimat- Tripolitania (western Libya), off Alge- fin tuna spawned in the Mediterranean ing the probable date and location of ria, and in the Black Sea. It is believed than in the Black Sea. Even though his hatching from the collection data of that additional research would show data are questionable, in view of present early stages. that the species spawns over a much knowledge, his conclusions were cor- broader area. rect. His work eventually led to the first The relationship between eastern doubts about the Aristotelian theory. D. SPAWNING AREAS AND Atlantic and Mediterranean bluefin tuna This was followed by d' Amico's SEASONS has been debated for centuries. An an- (1816) reve lation that bluefin spawned cient theory, proposed by Aristotle off Sicily. He noted that juveniles of 1. Mediterranean and Black Seas (circa 325 B.C.), has been believed for the species weighed about 42 g in June, centuries by the Mediterranean fisher- a. General Information 122 g in August and 840 g in October. men and repeated by many authors. The spawning habits of T. thynnus These data and those of Sella (1929a) His hypothesis was that the bluefin tuna thynnus have been more extensively enabled Heldt (1930) to present the lived in the Atlantic for most of the first growth curve for the early stages

70 of this species. Sanzo (1909, 191Ob) Center of the National Marine Fisher- Richards (l976) reidentified two described eggs taken from ripe bluefin ies Service at Miami, Florida. T.e. of Ehrenbaum's (1924) larval speci- caught off Sicily. Later Sanzo (l929, Potthoff (personal communication) mens, originally identified as 1932) described pelagic eggs which he identified 60 of the specimens which "Euthynnus alliteratus Raf. (?)", taken collected in the Strait of Messina in had been collected in Sicilian waters near the Balearic Islands in late August May and June, and larvae which were during the months of July, August and 1910, as Thunnus thynnus thynnus. hatched from these eggs and reared for September as Thunnus thynnus thynnus. Roule (l917) had tentatively listed.these six days. Sanzo concluded that these The lengths and the dates and localities islands as a spawning area for this spe- were the eggs and larvae of bluefm of capture of these specimens, which cies. In 1972 Duclerc et al. (1973) col- tuna, because the eggs matched those include the four largest ones reported lected eight bluefm tuna larvae near the taken from a ripe female, and the six- by Watson and Mather (1961), are Balearic Islands between June 20 and day-old larvae hatched from them shown in Table 16. July 7. They also collected pelagic eggs matched the smallest ofthe identifiable The most numerous records oflar- which fitted Sanzo's description of bluefm tuna larvae which he had col- val and juvenile bluefin tuna are from those of bluefin tuna, but, even after lected off Messina. More recently, how- Sicilian waters, but these forms have hatching some of these and raising the ever, several authors who have exam- been encountered in several other parts larvae for periods of up to four or five ined Mediterranean material have con- of the Mediterranean. days, they were unable to distinguish cluded that bluefin tuna eggs could not Roule (1917) cited Bourge's eggs of T thynnus thynnus from those be identified positively unless they were (1908) records which showed the ap- of "Auxis thazard'. hatched and the larvae were reared to parent growth of juvenile bluefin col- Dieuzeide (1951) listed the cap- an identifiable size (Piccinetti and lected off Tunisia. These young fish tures ofthree bluefin tuna larvae off the Piccinetti Manfrin 1970, Duclerc et al. weighed about 150 g in August, at- coast of Algeria June 7-8, 1940. He 1973, Scaccini et al. 1975). Collections tained 900 g in September, and ex- provided drawings of two of these, oflarger larvae and juveniles were also ceeded I kg in October. which were 5 and 6 mm long. reported (Sella 1924, 1929a; Sparta 1933, Padoa 1956, Scaccini 1965, Piccinetti and Piccinetti Manfrin 1970). Although Sella (l924) explained the Table 16. Collection data and lengths ofbluefm tuna from Sicilian waters, M.E, differences between juvenile T. thynnus Watson originally identified most of the specimens. T.e. Potthoff subsequently thynnus. T. alalunga and Auxis bisus, these early collections were not thor- confirmed her determinations and identified the remaining individuals. oughly described or illustrated. Recently Collection Area Scaccini (1961) and Scaccini et al. (1975) published a photograph of some Collection Date Standard Length (mm)' of Sella's material and reproduced drawings of larvae 4-12 mm long pre- 1. Straits of Messina pared under his guidance as well as July, 1949 17.4, 19.4,24,9,34.3,36.8,37,1 their own photographs of eggs, larvae 33,7 and juveniles. July 15 - Aug 31,1958 Watson identified and described, July - August, 1959 30.5, 31.0,31.0, 32.0, 34.2 with illustrations, larval and juvenile June 30 - July 1, 1960 16.9 bluefin from 11.4 to 37.8 mm long July 18 - 20, 1960 17,0, 17,7, 19.5,22.5,24.8,25.1,26.3,26.9 collected off Messina, Sicily, during July 24 - 25, 1960 17.7, 18.9,20.9,21.0,25.9,28.0,28.9 the summer months of 1958, 1959 and 1960 (Watson and Mather 1961), These July 26 - 27, 1960 32.4,33.4,34.5,38.5 identifications, based on external char- August 20 - 21, 1960 45.3, 50.4 50,S acters (Sella 1924) and osteological August - September, 1960 17,6 characteristics examined by radiogra- August 10 - 20, 1963 62.0,64.6,66.4,71.3,74.0,76.],87.5,99,6 phy, were subsequently verified by T.e. Potthoff (personal communication) of Unknown 12.6,15,5,16,7 the Southeast Fisheries Center of the 16.9,16.9,17,1,17.3,18.7,19.5,20,1, National Marine Fisheries Service, who 20.3,20,5,27.3,30.4 examined additional vertebral charac- 2.Palermo teristics after clearing and staining the August I, 1963 107.8, 117.5 specimens. Many additional identifications of The Messina specimens were purchased by the Woods Hole Oceanographic Institution juvenile Mediterranean bluefm tuna from G. Arena of Messina. The Palermo specimens were donated to the Institution by F, were obtained after the Woods Hole Tarantino of Dorchester, Massachusetts. All ofthe specimens were subsequently donated Oceanographic Institution collection to the Southeast Fisheries Science Center, National Marine Fisheries Service, Miami, was donated to the Southeast Fisheries Florida, and are now in its collection.

71 Recently, Piccinetti (I973), took relatively small maturing fish for dence indicates that they begin to spawn Piccinetti and Piccinetti Manfrin (1973), a considerable period after the conclu- later than the large ones, and that their and Piccinetti et at. (1976b) reported sion of the "arrival" fisheries for larger spawning extends through July well on occurrences of larval and juvenile maturing individuals in the Italian and into August, and sometimes even into Thunnus thynnus thynnus in the Adriatic Tunisian traps. September. This information is based Sea, the fIrst positive indication that the Heldt (1938) summarized the re- mainly on observations made in the species reproduced there. sults of Frade's histological studies of south-central Mediterranean. The Richards (1976) thoughtthat a lar- gonads ofbluefm tuna taken in various spawning periods in other parts of the val specimen collected off Cape Tunisian traps. Heldt had collected this Mediterranean and in the Black Sea, Matapan, Greece, on August 26, 1911, material and furnished itto Frade. Frade are not as clearly defmed. Reproduc- and originally identifIed by Ehrenbaum concluded that, if this small sample tion off the Balearic Islands evidently (1924) as "Orcynus germo Lacep. (?)" was representative, the various groups extends from mid-June at least to late was probably Thunnus thynnus thynnus. of tuna which frequent the Mediterra- August. Collections of eggs and larvae Richards agreed with Sella (1929a) nean do not mature simultaneously. The indicate that spawning in the Black Sea that the specimens identified by Ehren- fish taken off Tunisia were, in general, is at its maximum in the second half of baum (1924) as "Orcynus thynnus L. less mature than those taken in the east- July and early August, but conclusions (?)" were not of that species. ern Atlantic at the same time. based on catch records and gonad con- Several scientists have reported on Gonad studies related to the spawn- dition are inconsistent. eggs and larvae of bluefm tuna col- ing of bluefm tuna in the Black Sea The most completely documented lected in the Black Sea in mid and late depended mainly on material collected bluefin tuna spawning areas in the summer. Vodyanitskii and Kazanova near Istanbul, Turkey. Hovasse (1927), Mediterranean are off northeastern and (1954) reported that eggs and larvae after analyzing statistics of landings at western Sicily, and off the Balearic Is- were encountered there repeatedly in that city in 1915 and 1921-1923, found lands. Another apparently well docu- the second half of the summer, but two significant maxima in the catches, mented area is in the Black Sea. There mainly in the beginning of August. one in the spring (March-April) and are also strong indications of spawning Vodyanitskii (1936) and Oven (1959) one in the summer (July). There was off western Sardinia, northern Tunisia, described eggs found in the latter part also a minor maximum, whose signifi- and Tripol itania. More fragmentary data of July and in early August, off cance Hovasse did not understand, in suggest reproduction in the Adriatic Sevastopol and Karadag, respectively. the winter (December). He believed Sea, off Algeria and Greece, and in the Oven hatched some eggs and reared that the spring peak corresponded to a Aegean Sea. Scaccini et at. (1975) con- the larvae for up to eight days. northward migration into the Black Sea cluded that additional intensive research Many authors have presented in- and the summer one, to a southward will show that the spawning areas of T. dices of maturity for bluefm tuna taken passage back from the Black Sea into thynnus thynnus cover much more of inthe Mediterranean traps; we cite those the Sea of Marmara. He found that the the Mediterranean than was then be- of Sara (1964, 1973) because they are ovaries of the females taken inthe spring lieved. among the most recent. He found that were full, whereas those taken in July the first maturing fish taken in the Si- contained no eggs. AkyUz and ArtUz 2. Eastern and Central North cilian "arrival" traps in early May had (1957) stated that bluefin started to run Atlantic and the South Atlantic maturity indices of70-60, whereas those through the Bosphorus into the Black a. General Information taken toward the end of this fishery in Sea in April, and that this run peaked in Many experts have assumed that mid June had indices of about 25. An July and ended in September. The re- the Ibero-Moroccan Bay (west of index of about 40 was the most fre- turn migration occurred from late Oc- Gibraltar) contains the major, or the quent within the entire period. The fe- tober to November. Their studies of only, spawning grounds for T thynnus males were generally in a less advanced gonad condition indicated that spawn- thynnus in the eastern Atlantic. Exten- state of maturity than the males in this ing occurred in late July, August, and sive research in this area, dating from period. During the "return" run of pre- possibly September. lyigUngor (1957), the late nineteenth century, has pro- sumably spent fIsh, the first captures, however, listed three periods of pas- duced much information on the condi- in early July, were of fully mature fish sage: November-January, March-April, tion of the gonads of the bluefin tuna with indices of about 50. By late July, and July-autumn. Thus there are con- taken in the once flourishing trap fish- this had increased to 91, and in early siderable differences in the interpreta- eries in this bay. As noted in Section August, to 198. This decrease in matu- tions of the catch records in regard to IV, this fishery was divided into two rity was much more regular than the migrations and spawning. periods, the "arrival" (late April, May increase during the "arrival" run. Sella The above research shows clearly and June) and the "return" (July and (1929a), as well as Scordia (1932) and that spawning in the Mediterranean by August). During the "arrival" period, Sara (1973), noted that small maturing large bluefin tuna starts about mid-June the fish are apparently travelling along or ripe fish were sometimes taken in and ends about mid-July. The repro- both coasts of the bay in the general the Sicilian return traps, along with the duction of the smaller (the medium- direction of the Strait of Gibraltar. In spent large ones, in July and even in sized and some of the larger "small" the "return" fishery, which occurs only August. Sella and Sara also pointed out individuals) fish has not been investi- along the Iberian coast, they seem to be that the "arrival" traps in Tripolitania gated as thoroughly. The available evi- travelling westward. The "arrival" traps which have been used within recent Evidence of reproduction of th~ ally about ].5, to make the indices for years were distributed from Cabo de species in other parts of the eastern males comparable to those for females Santa Maria in Portugal to Tarifa, Spain, Atlantic, and inthe central and the South at the same stage ,of maturity. Even and along the Moroccan coast from Atlantic (Figure 65), is very meager. though these corrections did not pre- Kenitra to Cape Spartel, Morocco (Fig- Some larvae have been collected in the vent the occurrence of similar indices, ure 44). It should be noted that the two eastern equatorial Atlantic. A few oci," in the intermediate stages, for pre- latter localities are at the very entrance currences of ripe bluefm in the Bay of spawning and post-spawning fish, he of the Strait of Gibraltar. Some of the Biscay have been reported. Spawning felt that this procedure clearly showed Portuguese and Spanish traps were re- in the vicinity of the Azores has been the progressive emptying of the go- arranged at the end ofJune to fish in the suggested. A spawning area between nads, or the fractional emission of the "return" period. Lanzarote, one of the Canary Islands, spawning products. His stages are The gonad studies showed that the Conception Bank, and the Moroccan shown in Table 17. "arrival" fish were maturing and that coast has been hypothesized, but not Frade (I 937a) presented the indi- their indices of maturity became lower investigated. ces obtained for ]71 bluefin tuna px- (indicating more advanced maturity) amined at Vila Real de Santo Antonio, b. Specific Occurrences as the season progressed. On the other Portugal, from May 31 to August 18, From numerous studies of the con- hand, the "return" fish were generally 1933 (Table 18). These same values dition of the gonads of bluefin tuna spent, with their indices of maturity are shown graphically in Figure 66. caught in the Ibero-Moroccan Bay, we increasing (indicating shrinking of the Frade reached the following conclu- have selected for discussion those of gonads) toward the end of the season. sions: Frade and Manayas (1933) and Frade Since the more mature ovaries were an (I 937a) for Portugal, F. de Buen (I 927) 1) Ripe and intermediate stages (A- important by-product of the fishery (F. and Rodriguez- Roda (1964a) for Spain, D) of both sexes are represented in de Buen 1928), these facts were known and Lozano Cabo (1957, 1958) and June, but in decreasing frequen- to the fishermen for centuries before Furnestin and Dardignac (1962) for cIes. the scientists arrived on the scene. In Morocco. fact, they may have played a role in the 2) In July intermediate stages (C and Frade and Manayas (1933) pre- development of Aristotle's migratory E) predominate among the females, sented one of the few histological stud- theory. and in the males, late intermediate ies on the stages of maturity of the This, simple combination of cir- and spent stages (E and F) appear. gonads of bluefin tuna which are avail- cumstances was interpreted in opposite able. Their observations confirmed the ways by the proponents of the "Atlan- 3) In August intermediate stages (0 fractional nature ofthe spawning of the and E) are predominant for the fe- tic-Mediterranean migration" or "mi- species. This accounts for the lack of gratory" theory and the advocates of males while ripe and intermediate completely ripe fish in the traps, be- "separate Atlantic and Mediterranean stages (B and C) are still pre- cause all the eggs destined to be emit- dominant among the males. Some populations" or "sedentary" theory. The ted in a given season do not mature former maintained that these facts indi- fish of both sexes have attained the simultaneously. A large number of the cated, that many of the "arrival" tuna fully spent stage (G) and females individuals entering the traps in the in the fully ripe stage (A) have entered the Mediterranean to spawn, "arrival" period may have already emit- and that the "return" run included many disappeared from the catches. ted part of their spawning products. In individuals which had spawned in the F. de Buen (1927) noted that blue- addition the small bluefin I m long Mediterranean and were returning to fm tuna which had arrived to spawn feeding areas in the Atlantic. The latter (about 3 years of age) behave differ- were caught in the southern Spanish ently according to their sex. The males believed that few, if any, of the "ar- Atlantic traps in April, May and June, are in active or terminated spermato- rival" fish passed through the Strait of and that they also entered these traps genesis, whereas the females are in very Gibraltar and that most of them beginning in July, after spawning. Af- retarded ovulation. spawned in the Ibero-Moroccan Bay. ter exam ining a large number of speci- Later Frade (l937a) described a Despite the many decades of in- mens from these traps in 1923, he con- simple method for determining stages tensive research on bluefin tuna in the cluded from the data that in ]923 the of maturity consistent with the abso- area, however, no identifiable eggs, lar- bluefin spawned in the Ibero-Moroc- lute ones established by his histologi- vae or juveniles (as defined here) of can Bay in the months of June and July, cal studies (Frade and Manayas ]933). bluefin tuna have been collected in the and that the males had attained sexual To offset the effect of seasonal varia- Ibero-Moroccan Bay. maturity before the females (Table 19). tions in the length-weight ratio, his in- In addition to the gonad studies, a In one of his major works on the great deal of other biological informa- dex of maturity was the quotient ofthe biology of the bluefin tuna taken in the weight of the head, rather than the total tion pertinent to the possible spawning traps off the southern coast of Spain, of the species in this area has been weight of the fish, divided by the weight Rodrfguez-Roda (l964a) provided published. Extensive data on the prop- of the ovaries. He also used a factor K much information on the variations in .erties of the environment are also avail- (the ratio of the weight of ovaries to the gonad condition through the spawning able. weight of testes at the same stage, as season. He set up the following scale determined by histological studies, usu-

73 which were in stages I and n were not large individuals. Those in stage I in June were 95 and 80 em long, respectively. Those of both sexes in stage II were 115 to 140 em long, excepting two females 170 and 175 em long. In July and August a few bluefin were in the prespawning state. One male 135 em long was in stage n in July. Males and females from 125 to 220 em long in July, and 125 to 135 em long in August, were in stage III. The only specimen in stage IV was a male 170 em long taken in June. Rodriguez- Roda (1964a) also used an index of maturity, the "gonosomatic relation", equal to 100 times the ratio of the weight of the gonads to the total ~ KDawn "ajor BpaWlling Ar••• weight of the fish, to evaluate relative fecundity. He also provided plots and ....• formulae showing the relationships be- ilia ••., Una_ualed Dr Bypothetlcal tween the weight of the gonads and the BpaWDInlareu fork length of the fish for bluefin tuna during the "arrival" and "return" periods. He tabulated the gonosomatic relation for males and females, by 5-cm length groups and 10-day periods, for 260 "arrival" and "return" fish examined in 1956, and also for 198 examined in 1958 (Tables 21a and 21b). This index generally increased with Figure 65. Bluefin spawning areas in theEastern Atlantic and the Mediterranean size of fish. Its mean value also in- and Black Seas. creased during the "arrival" period in June, for both sexes, then descended abruptly in the months of July and Au- for stages of maturity, based on the riod and it was concluded that its ovi- gust, in the "return" period. All this confirnled spawning in early July. In color ofthe ovaries: duct was probably obstructed. general, the index was higher for fe- I. Immature: Gonads of rosy color. During the "arrival" run in May and June the bluefin tuna appeared with males than for males. n. Prematuration: Male gonads of a turgid gonads in a state of prematuration The condition of the gonads of violaceous color, and female of a or maturation and in the "return", in bluefin tuna taken off the Atlantic coast rose color. July and August, the gonads were al- of Morocco was examined by Lozano ready flaccid and with obvious signs of Cabo (1957, 1958) and Furnestin and Ill. Maturation: Male gonads of a having emitted the eggs. Between these Dardignac (1962). Lozano Cabo (1958) rose or a rosaceous white color, two phases, at the end of June and early tabulated, by sex and 10-day period, and female yellow rose or yellow- in July, when spawning should actu- the minimum, mean, and maximum ish. ally occur, the bluefin disappeared from indices of maturity of samples of blue- the coast and its captures were very fin tuna taken in 1955 by the trap at Los IV. Prespawning: Male gonads of a Cenizosos (near Larache) in 1955 milky violaceous color. limited. To define the spawning period, (Table 22). V. Spawning. the monthly percentages of the sexual The mean index for females de- stages for 779 males and females ex- creased from 80.8 in the last ten days of VI. Postspawning: The male and fe- amined at the Barbate trap from J 956 May to values between 46.2 and 40.0 male gonads are ofa violet color. to 1959 are shown in Table 20. in the three ten day periods in June. In Very swollen ovaries with most of The majority of the fish were in a the second ten days of Maya few fe- the eggs transparent were considered prespawning state (stage III) in May males with very low maturity (indices to be in stage V. Only one such female and June and in the post-spawning stage averaging 105.3)wereexamined. When was observed during the "return" pe- (stage VI) in July and August. The these fish were being taken, the catch small percentage of tuna of both sexes was very small. The fishery did not

74 Table 17. Indices of maturity and condition of gonads (Frade I937a). become productive until the index reached 63.6 (Lozano Cabo 1957). The Indices of Maturity Condition of maturity of the females decreased Stage Female Male Gonads slightly (index rising from 40.0 to 43.9) from the second to the third ten days of June. This was caused by the capture of A Up to 7 Up to 10.5 Full some spent, post-spawning, or "return" B 7 - 12 10.5 - 18.0 " fish in this "arrival" trap. The only in- C 12-17 18.0 - 25.5 " dices for males, taken in the last ten D 17 - 22 25.5 - 33.0 Intermediate days of May, ranged from 42.7 to 131.2, with a mean of76.8. These figures do E 22 - 27 33.0 - 40.5 " not differ greatly from those for fe- F 27 - 32 40.5 - 48.0 Empty males taken in the same period. G 32 - 37 48.0 - 55.5 " Furnestin and Dardignac (1952) tabulated the mean "gonado-somatic indices" (evidently the "gonosomatic relation" of Rodriguez-Rod a 1964a) for males and females taken in the trap at Table 18. Stages of maturity for 171 bluefm tuna examined at Vila Real de Santo Moulay-bou-Selham (near Kenitra) in Antonio, Portugal, May 31-August 18, 1933 (Frade 1937a). the frrst and second halves of May and the first half of June (Table 23). The indices for males increased FEMALES rather regularly from l. 10 in the frrst A B C D E F G half of May to 2.04 in the first half of 29 Tuna 13 11 4 1 May 3 I-June 5 June. Those of the females followed a % 45 38 14 3 similar trend, from 1.52 to 1.99 over the same period. These values showed 21 Tuna 3 5 7 4 2 a more consistent increase in maturity % 14 24 33 19 10 July 7-18 through the season than those of Lozano 54 Tuna 3 10 15 14 6 6 Cabo (1958). Furnestin and Dardignac % 6 19 28 26 11 11 August 5-18 (1962) also plotted the gonado-somatic indices for each sex against the length MALES of fish. Those for females increased A B C D E F G with length, but those for males only increased up to a length of21O cm and 16 Tuna 9 3 2 2 May 3 I-June 5 decreased slightly in longer individu- % 56 19 13 13 als. The authors attributed this to the 17 Tuna 3 8 4 1 1 July 7-18 fact that the largest fish were caught at % 18 47 24 6 6 the beginning of the season, when their maturity would normally have been less 34 Tuna 1 8 9 4 6 3 3 August 5-18 advanced. The maturity of the fish taken % 3 24 26 12 18 9 9 in the frrst half of June at Moulay-bou- Selham is generally comparable to that found by Rodriguez-Roda (I 964a) for fish taken at Barbate, Spain, in the frrst twenty days of June. Lozano Cabo 60 (I 958), however, reported thatthe bluefm tuna which he examined at Los 50 Cenizosos were less mature than those ••••40 which he had examined at Barbate. Ci There is strong circumstantial evi- ~30 dence that bluefin tuna spawn in the ~ 20 Ibero-Moroccan Bay, but conclusive 10 proof of this is lacking. Great numbers o of maturing individuals occur there in May and June, and recently spent fish are abundant in July and August. The stages of maturity of these fish have Figure 66. Plot showing the changes in sexual maturity of Atlantic bluefin tuna been verified by many investigations. by month. The data are the same as in Table 18. On the other hand, much research and

75 Table 19. Bluefin maturity by month from the trap fishery alOligthe southern tion of their gonads. The ovaries of Atlantic coast of Spain (F. de Buen 1927)... very few specimens among the bluefin landed in the period )un~., 16-30 were Males Females ripe. The fish landed in this-period were % Not % Fully % % Not % Fully 010 in the 15-25 kg weight range. Creac'h (1952) noted that a similar situation Month Mature Mature Spent Mature Mature Spent had been observed for the first time, in about the same period, during the 1950 May 100 0% 0 100 0 0 season. No observations of mature fish June 32 60 8 67 30 3 during the remainder of the season were reported. July I 33 66 26 12 62 Cort et al. (1976) and Cort (1977) 0 100 August (beg.) 0 0 100 0 provided the first detailed information on the gonads of maturing bluefm taken in the Bay of Biscay. These authors two intensive surveys have failed to Saavedra" conducted an intensive examined four bluefin 125-149 em long produce a single identifiable egg or planktonic and hydrographic survey of taken in the Bay of Biscay June 25-26, early stage (less than 10em long) of the the waters east and west of Gibraltar in 1976, and seven III to 161 cm long species from the area. 1972. The period of the survey, 19 taken there on July 15, 1976. On the O. de Buen (1924) and F. de Buen June-16 July, was chosen because this basis of color (Rodriguez- Roda I964a), (1924, 1925, 1927) failed to find any was regarded as the period of maxi- they estimated that the two males in the eggs or early stages of bluefin tuna mum spawning of bluefin tuna in the frrst group were fully mature, whereas during their intensive 1923 survey of area (Rodriguez-Roda 1975). During one female was in pre-spawning con- the Ibero-Moroccan Bay, west of this cruise 66 stations were occupied in dition and the other specimen was spent. Gibraltar, and the Alboran Sea, east of the Atlantic, four in the Strait of They classified three females in the it. They explained this apparent contra- Gibraltar, and 82 in the Mediterranean second group as pre-spawning and two diction of their theory that the Ibero- (Rodriguez-Roda 1975). No identifi- as spent, and considered one male to be Moroccan Bay was a major spawning able larval orjuvenile bluefin tuna were fully mature and the other spent. ground for bluefin tuna, and that the collected. Cort et aI. (1976), using the tech- maturing fish did not enter the Medi- Until eggs or early stages collected nique ofRodriguez-Roda (1967), mea- terranean to spawn, as follows. The in the Ibero-Moroccan Bay are posi~ siJred the diameters of eggs from two bluefm spawned in this Bay, but the tively identified as those ofbluefm tuna, females, 148 and 152 cm long, of the eggs and larvae were carried from it by this area must be regarded as only a second group. The diarrietersdfor the the surface (Atlantic) current into the hypothetical spawn ing area for thisspe- 148 cm specimen ranged from 0.10 to Mediterranean before they attained full cies. 0.66 mm, with many from 0.22 to 0.58 mobility. There they accumulated off F. de Buen (1937) proposed a sec- mm and the highest mode at 0.50 mm the Moroccan coast between Punta ond spawning area for the eastern At- Those from the other ranged from 0.14 Almina and Cape Tres Forcas, where lantic bluefin in the southeastern cor- to 0.58mm, with most betWeen 0.30 the rich plankton provided food for the ner of the Bay of Biscay. This hypoth- and 0.53 mm and a wide mode be- early stages. Roule's (1923) contrary esis was based on reports of bluefin tween 0.40 and 0.46 mm Theyc1assi- view, that bluefm larvae were abyssal with ripe ovaries being taken there in fied these fish as in stage IV (pre-spawn- and· were passively transported from June. Le Gall (1952) reported similar ing) or between stage III (maturation) the Mediterranean into the Atlantic by findings there during the 1950 and 1951 and stage IV, since the diameters were the deep outflowing (Mediterranean) seasons. Creac'h (1952) described the greater than those of the ova and 00- current will be discussed in Section sizes of bluefm tuna landed at Saint- cytes of the specimens placed by VE2. More recently, Spanish scientists Jean-de-Luz through the 1951 season Rodriguez-Roda (J 967) in stage III. in the research vessel "Com ide de (April 12-0ctober 26) and the condi- Cort (1977) noted that these observa-

Table 20. Monthly percentage of the sexual stages (years 1956-1959) of tuna at Barbate (Rodriguez-Roda I964a) ..

Sexual Stae;es of Males. Number = 284 Sexual Stae:es of Females. Number = 495 Month I II III IV V VI I II III IV V VI

May 100.00 100.00 June 0.62 3.09 95.06 1.23 0.41 3.26 96.33 July 1.85 5.55 1.85 90.74 9.46 90.54 August 3.17 96.82 1.06 '. 98.94·

Table lib. Variation of gonosomatic relation· with length offish and period of capture for' male and'ferriaJe bluefin tuna taken in the Barbate trap in 19SS (Rodrfguc::~~RPda1964a).

"- Fork Lenph: 1211-124.5 125-129.5 1311-134.5 135-139.5 1411-144.5 145-149.5 1511-154.5 155-159.5 160-164.5

Males (Arrivals) June 1-10 2.67 1.90 1.48 1.54 1.29 1.63 June 11-20 258 1,92 1.39 June 21-30 Males (Returns) July 20-20 0.87 Aug 1-10 0.60 0,52 Females (Arrivals) June 1-10 0.95 1.54 1.04 2.47 1.25 0.72 2.13 2.02 June 11-20 1.10 1.78 1.70 1.26 1.40 1.62 June 21-30 Females (Returns) July 20-30 0.77 1,04 Aug 1-10 0.77 0.81 0.69 0.80

Fork Lenph: 165-169.5 170-174.5 175-179.5 180-184.5 185-189.!1I90-194.5 195-199;5 200.%04.5 ' %05-%09.5

Males (Arrivals) June 1-10 1.32 1.30 2.41 1.69 1.38 1.22 June 11-20 2.02 1.73 2.06 ],87 1.86 June 21-30 Males (Returns) .. July 20-30 1.10 • 0.80 0.63 Augl-IO 0.66 1.00 0.68 0.55 0.81 0.44 0.60 Femllle's (Arrivals) June 1-10 2.14 1.95 1.50 2.13 1.46 1.33 1.60 1.00 lune 11-20 1.37 1.64 1.34 1.75 2.05 1.75 1.53 3.14 June 21-30 Females (Returns) July 20-30 1.18 0.90 1.19 1.00 1.16 Augl-IO 0.67 0.80 0.92 0.84 0.69 0.88

Fork Lenph: 1111-11405, 115-219.5 • %211-%24.5%25-%29.5 230~234.5 %35~%39.5 %40-%44.5 %45~%49.5 '%50·%54.5 n ' .··.·.Mean

Males (Arrivals)

June 1-10 2.51 2.13 1.30 1.99 3\ 1.73 June 11-20 1.07 2.25 1.73 15 1.91 June 21-30 2.64 2.76 3.06 6 2.87 Ml!llcs(!{eturns) luly 20-30 0.64 0.90 0.72 0.47 , 0.6] 12 0.72 AuS 1-10 0.42 0.48 0.47 13 059 ,F.cl1Iales(Arrivals) June 1-10 1.98 1.89 , 2.11 41 1.65 June 11-20 2.49 2.47 2.17 38 1.68 June 21-30 1.94 1.94 ,Fe~~I~ \J;leturns) July 20-30 0.72 0.74 0.89 0,,94 17 0.96 Aug 1-10 23 .0.89

-Maturity index obtained by multiplying the ratio ?f the ,,:,eight of the g~rlldstothe total. weight ofthetish by 100 (RlJdrlgue:?:-Rod~,I964a) . --, ' '" , , . .. .. ,. .•.•• ,.~, ,.~ _._ h _", ., .' ..• -,',;", ' ~.: _" ••v •• ·• .••. ~--"- .,-, ..,-, ~ "' .•..-".-~, ......

78 Table 22. Indices· of maturity for 140" bluefin tuna taken in the Los Cenizosos Atlantic and Mediterranean tuna, if they trap (near Larache. Morocco) in May and June 1955 by sex and 10-day period are indeed separate, is another impor- (Lozano Cabo 1958). tant matter about which there is no quantitative information. In view of the Indices for Females Indices for Males possible passive transport of spawning Month Min. Avg. Max. Min. Avg. Max. products from the Ibero-Moroccan Bay into the Mediterranean, the technique of collecting pelagic eggs, hatching May 20-30 37.1 80.8 142.8 42.7 76.8 131.2 them, and rearing the larvae to identifi- June 1-10 25.4 46.2 62.7 able size appears to be the most prom- June 11-20 30.0 40.0 52.0 ising approach to solving the important problem of whether bluefm tuna actU- June 21-30 43.9 ally spawn there. The failure to fmd •The indexof maturity isthe ratio of the totalweight ofthe fishto the weightof itsgonads. identifiable eggs or early stages of bluefm in the Alboran Sea (westernmost ••Seventy-sixwere examined individuallyinthe first three periods.The index for the last Mediterranean) as well as in the Ibero- period was obtained by dividing the total weight of64 fish by the total weight of their Moroccan Bay during the 1923 and ovaries 1972 surveys, however, does not support the theory of passive drift of spawn from the latter area to the former.

3. Western North Atlantic

a. General Information tions were too few to be conclusive, Atlantic bluefin are believed to spawn. Important information on the but hoped that future research might The oceanic distribution of blue fin tuna spawning of Thunnus thynnus thynnus determine the possible existence of a (Wise and Davis 1973) in the first quar- in the western North Atlantic has been bluefm spawning ground in the Bay of ter of the year shows concentrations of obtained through collections of larvae Biscay. bluefin near where these larvae were and juveniles. Ripe or nearly ripe fish Aloncle (1964) found that many found, but the distribution in the third have been captured over extensive ad- 30-60 kg bluefm wintered between the quarter does not. It would be desirable ditional areas. Canary Islands and Morocco and hy- to conduct a survey in this area in the The great majori~ oftre captures pothesized that one group of them second quarter, and also to examine the of larvae and juveniles have occurred spawned between Lanzarote Island (Ca- gonads of bluefin caught there in the in the Gulf of Mexico and the Straits of naries), Conception Bank, and the Mo- months of February through August. Florida. Scattered occurrences farther roccan coast. Distributional data sup- Much remains to be learned about north include one larva east of northern port this hypothesis, but studies of go- the spawning of blue fin in the eastern Florida and seven juveniles (17.5-33.2 nad condition and collections of eggs Atlantic, and about the possible role of mm SL) off the Carolinas, Maryland and early stages are required to verify the Mediterranean, both as a spawning and New Jersey (Figure 67). it. ground and a nursery area for bluefin Occurrences of ripe or nearly ripe Ferreira (1932) reported that ripe tuna from the eastern Atlantic. The de- fish have spread over some additional bluefin were sometimes landed in the gree of mixing of adults and new-born Azores in spring, but his statistics indicated that the species was not abundant there. The only reports of larval bluefm taken in the eastern Atlantic are from Table 23. Variations in the mean gonado-somatic indices" of blue fin tunab taken equatorial waters off Africa. Fourteen in the trap at Moulay-bou-Selham (near Kenitra, Morocco) in May and June, small larvae (mostly 2.5-4.5 mm long) 1955 (Furnestin and Dardignac 1962). were taken in the area bounded by latitudes 6°N and· 80S and longitudes 0° Sex May 1-15 May 16-31 June 1-15 and 15°30'W. One of these was collected in February, eight in March and Males 1.10 1.25 2.04 five in August (Richards 1969,Richards and Simmons 1971, unpublished (n=21) (n=9) (n = 75) NMFS data reports for Geronimo Females 1.52 1.42 1.99 cruises 3, 4 and 5). The surveys in (n = 8) (n = 18) (n = 91) which these collections were made were carried out in the periods February- "Thegonado-somatic index is 100times the ratio of the weight of the gonads to the total April and August-October, missing weight of the fish. bTheterm n is the number offish in each sample. most of the period in which the eastern

79 areas. They include several medium- areas (Juarez, M. 1974b, Montolio and other, 101 to 331 at three stations, and sized (32-125 kg) bluefui as well as a Juarez, M. 1977) (Figure 68). The rela- 100 or less at eight stations. No bluefm few larger individuals, in the area tive abundance of larvae per 100 m2 were captured at the other 33 stations. bounded by latitudes 37°30'N to was calculated by the formula: The estimated number of larval T. 40030'N and longitudes 66~O'W to thynnus thynnus in the area, on the NT/V X 100 700oo'W, well north of nearly all of the basis of Juarez's (1974b) data, was s recorded captures of larvae and small where: 3 1,442 X 10 (Richards 1976). Bluefm juveniles in the western North Atlantic. tuna constituted 24.6 percent of all of Nearly ripe large bluefm tuna have also N is the number of larvae per tow, the larvae of the family Scombridae been encountered in the northwestern collected during this cruise (Juarez T is the depth ofthe thermocline and Caribbean Sea and northeast of the Ba- 1974b). hamas, where no larvae or small juve- V is the volume of water filtered in Bluefin tuna larvae were much l niles have yet been found. m . more available during the May to June The capture oflarvae depends not 1974, cruise, which sampled nearly all In the 1973 cruise, which covered only on their abundance but also on the of the deep (over 200 m) waters of the the eastern half of the Gulf, larvae were intensity and seasons of the collecting Gulf. Larvae of this species werecol- taken in varying numbers at 13 of the effort. Additional planktonic surveys lected at 23 of the 61 stations occupied 46 stations which were occupied (Juarez in the proper seasons would probably (Montolio and Juarez 1977). All of the 1974a, I974b). Most of the larvae were have extended the areas of known oc- successful stations were between lati- captured in the north central Gulf at 11 currences of larvae and smalljuveniles tudes 23° and 28°30'N, and longitudes stations within the area bounded by considerably. 84°30' and 94° 30'W. Nearly all of latitudes 25°N and 30° N and longi- them were between 40 and 140 nauti- tudes 87°W and 91°W. Others were b. Specific Occurrences cal miles (74 and 140 km) from the 200 taken at a station at about 26°N latitude The most numerous and wide- m contour. Five stations yielded more and 84°30'W longitude, and another at spread collections of larval and juve- than 1,000 bluefm per 100 m2 each. about 24°N latitude and 88°W longi- nile bluefin tuna from the western North These stations were rather scattered, tude. Atlantic area were taken in the Gulf of with one at 24°N, 87°W, another !it The April to May collection data Mexico. During extensive 28°N, 87°W, one at 27°30'N, 900W, ichthyoplankton surveys of the Gulfby indicated relative abundances of blue- 2 and two near 26°N, 94°30'W. From fin larvae of up to 2,000 per 100 m • the Centro de Investigaciones Pesqueras 501 to 1,000 per 100 m2 T. thynnus Relative abundance of larvae of Cuba in April to May 1973, and in thynnus larvae were taken at five sta- (number per 100 m2 of sea surface) May to June 1974, numerous bluefm tions well spread over the area. ten tuna larvae were taken over extensive were 2,000 for one station, 649 at an- 2 stations produced 101-500 per 100 m , and only two of the successful stations yielded 100 or less. Results at one positive station were not reported. No blue-

- - -F-~5 fin larvae were collected at the 38 re- /,- -zoo- 0 maining stations. The larvae of T. thynnus thynnus constituted 47.7 per- 40° ;JUL-2 LEGEND .. ~,..•. cent of all of the larvae of the family o LARVAL <13mm >,~.~;,A- JUL-l Scombridae which were collected dur- + JUVENILE 13-120mm ,';, ,J ing this cruise (Montolio and,Jaurez MONTH-N=NUMBER CAPTU .,: I ,'..: +,'MAY-3 1977). . f MAY-t The May to June 1974 cruise showed that the spawning of bluefm extended over much of the deep water of the Gulf of Mexico north of 23°N latitude in that period. Comparisons with the results of the April to May 1973 cruise suggest that bluefm tuna larvae are much more available in the Gulfin May and June than in April and May, and consequently that spawning is more intense in June than in ApJ;il. This is in agreement with other available indications, but this comparison might have been biased by better spawning success in one year than the other. Figure 67. Collection locations for larval andjuvenile bluefin tuna in the western "Numerous" bluefin tuna larvae North Atlantic. 4.2-] 0.2 mm SL were collected at

80 23°50'N latitude, 88°40'W longitude Another important series of col- four stations (oblique tows at station on May 17, 1972 (Juarez 1972). lections of blue fin larvae was made off number I near the Miami harbor en- Considerable quantities of these larvae Miami, Florida, with surface tows (from trance buoy were omitted because the were also collected near this location in 1969 to 1971) and on a transect from depth of the water was insufficient). the subsequent surveys of April to May Miami to Bimini, Bahamas, with sur- The catch rates in numbers of larvae 1973 and May to June 1974. face tows and oblique tows to 200 m per tow (both types combined) were T.C. Potthoff (personal communi- depth (in 1975) (Richards 1976). The maximum, 0.8 and 0.6, at stations 2 cation) reported the collection of one cumulative numbers of surface tows and 3. Lower catch rates, 0.1 and 0.2, larval T. thynnus thynnus 5.5 mm SL and captures of larval bluefin tuna are were obtained at stations I and 4, and June 29, 1969, and four larvae 3.6-4.2 listed by half-month periods in Table no larvae at all were caught at station 5 mm SL on July 6, 1969, in the northern 24. In total, 93 tows were made, and on the Bahamas side of the Straits. This Gulf of Mexico near 29°N latitude and 164 identifiable bluefm tuna larvae of distribution is rather surprising, as large 87°W longitude. Thus, these were cap- 3.3 to 7.2 mm SL were collected, an bluefin tuna are observed and caught in tured near the northeastern boundary average of 1.8 larvae per tow. The tows considerable numbers along the edge of the area where Juarez (1974) and extended over a period from April 2 to of the Great Bahama Bank near Bimini Montolio and Juarez (1977) took most July 8, but bluefm larvae were taken in May and June but are a rarity on the of their specimens, but the dates of between April 22 and June 26 only. Florida side (Rivas 1954, Mather capture extend the time of occurrence The number oflarvae per tow was only 1963a). A single larva (8 mm SL) col- of the bluefin tuna larvae in the Gulf of 0.1 in the second half of April, but rose lected off St. Augustine, northeastern Mexico into July. to 1.8 to 3.5 in the half month periods Florida, (Figure 67) in May 1968 (T.C. Richards (1977) provided addi- of May and June, with maxima in the Potthoff, personal communication) tional data on occurrences of bluefm first half of May and the last half of completes our knowledge of the distri- tuna larvae in the Gulf of Mexico. Nine- June. bution of bluefin tuna larvae in the teen larvae ranging from 3.9 to 7.4 mm During the transects in 1975, 39 western North Atlantic system. SL were collected near 27°N latitude, larvae 3.4-7.3 mm SL were collected The known range of small juve- 96°W longitude, on May 6, 1975, and in 61 surface tows at five stations, and nile (12-120 mm SL) bluefm tuna in- May 30-June 6, 1976. 23 were collected in 47 oblique tows at eludes much of that covered by the larvae, but extends considerably farther north (Figure 67). Rivas (1954) collected a 45 mm SL juvenile off Mi- ami on June 9, 1953. Potthoff and Richards (1970) identified 40 juvenile bluefm 22- I 18 mm long which had 35° 0 been regurgitated by terns during a tern- 7 banding operation at the Dry Tortugas, + Florida, in June and the first half of July 1960-1967. None were found in 6• May, although juveniles of other • scombrids were collected. No scombrids less than 20 mm long were collected in this manner. Twenty addi- tionaljuvenile bluefin in the same general size range and season have been obtained from terns at the Dry Tortugas subsequent to the 1970 publication (T.e. Potthoff, personal communication). T.C. Potthoff (personal communication) also informed us offivejuve- nile bluefm 22-33 mm long collected in the Gulf of Mexico in late May and early June, and four others, 16-21 mm long collected off the Carol inas in May. A most surprising record, also provided by Potthoff, was of a 17.I mm SL juvenile collected off Mobile, Alabama, on August 19, 1954. This specimen must have been spawned long after adult bluefin have usually left the Gulf, and also in a month when the extensive Figure 68. Bluefin tuna larvae sampled in the Gulf of Mexico. Cuban ichthyoplankton survey in 1973

81 failed to colIect a single larva of this of milt present, as recently spent, partly ware", R. H. Gibbs and B. B. Collette, . species (Juarez 1974b). Three juveniles spent, or ripe. then of Woods Hole Oceanographic 21-33 mm long colIected off Maryland All ofthe 29 males exam ined were Institution, macroscopically examined (37°42'N latitude, 73°10'W longitude) classed as recently spent. He also con- the gonads of 48 bluefm tuna caught and New Jersey (38°45'N latitude, sidered that 61 of the 66 females exam- during the period June 8-14, 1957, in 7lo00'W longitude) July 27-28, 1959, ined were recently spent, but one was the area between latitudes 37°30'N and have been identified as bluefm tuna by judged to be partly spent, and four were 40030'N and longitudes 66°W and Watson (Watson and Mather 1961) and considered ripe. 70oW. Their observations were repro- this identification has been verified The smaller eggs of ripe females duced by Baglin (1976). Two age-3 (T.C. Potthoff, personal communica- were non-spherical, opaque and mea- (95-105 cm) individuals were consid- tion). These records are the most north- sured 0.4 to 0.7 mm in diameter, with a ered immature. The testes of one male erly in the western Atlantic for small mode at about 0.6 mm. The larger eggs of age 4 (121 cm) contained abundant juvenile bluefm. They are of special were spherical, translucent, yolk-filled, milt. Two other males and two females interest because they are from the area and measured 0.7 to 1.1 mm in diam- of this age group were classed as im- where medium-sized bluefin may eter, with a mode at about 0.9 mm. mature, but the ovaries of another age- spawn (Mather 1974, Baglin 1976). The Rivas (1954) offered two possible ex- 4 female were "much vasculated," a spawning habits of these fish in the planations for the small number of ripe sign of ripening. Milt was squeezed western Atlantic are little known, but individuals (about 4%) found in com- from the testes of a 5-year-old (140 they do not occur in numbers anywhere parison with the larger number (about cm) male. The ovaries of a female of near the known spawning areas of the 96%) of spent individuals. Since the the same age-size group were preserved large bluefin (Mather 1963a; also see fish which are observed in the area are for laboratory examination, presumably Section IV). nearly always travelling northward, it because ofsigns of maturity. Six males Examinations of gonads suggest was possible that they had spawned in and six females, probably 6 years old. that the spawning grounds ofthe blue- an area south, or southwest, of the fish- (143.5-157.2 cm), were examined. The fin tuna in the western North Atlantic ing area near Bimini and were caught testes of all of the males contained abun- may be much more extensive than is when spawning had been nearly com- dant sperm; those of one individual indicated by the distribution of catches pleted. He assumed that they had mi- were much enlarged, and another was of larvae, or even of juveniles (Mather grated to this area through the Straits of classified as ripe. One female was 1974, Baglin 1976). Florida, passing close to Havana, Cuba, classed as "near ripe." The ovaries of Rivas (1954) examined the gonads and the western edge of Cay Sal Bank. another contained eggs which seemed of95 large (199.7-255.0 cm long) blue- The other possible explanation which to be nearly ripe, but were not loose. fm tuna caught near Bimini, Bahamas, Rivas offered was that the rod and reel Those of two others were well devel- all in the month of May, but in three fishing method used at Bimini selected oped and loose, indicating imminent different years, 1952, 1953 and 1954. spent rather than ripe fish. He quoted spawning. The ovaries of the last two He classified the specimens, by the color previous authors on the reluctance of females of this group contained no eggs, and consistency of the gonads, the na- spawning fish to feed. and were believed to be spent. ture of the ovarian eggs, and the amount During cruise 57-5 of the Bureau These observations, and less nu- of Commercial Fisheries M/V "Dela- merous ones from later catches of the

Table 24. Number of surface tows and number of larvae collected 25 nautical miles (4.0 km) from the Miami harbor entrance (Station 1) (1969-1971 and 1975) and additional stations (2-5) completing a transect of the Straits of Florida from Miami to Bimini, Bahamas, in 1975-. Data are from Richards (1976).

Station 1 (1969-71, 1975) Stations 2-5 (1975) Total Date Tows Larvae Larv.rrow Tows Larvae Larv.rrow Tows Larvae Larv.rrow

April 1-15 6 0 0 8 0 0 ]4 0 0 April 16-30 5 I 0.2 4 0 0 9 ] 0.1 May 1-15 8 45 6.7 8 7 0.9 16 52 3.2 May 16-31 6 6 1.0 8 20 2.5 14 26 1.8 June 1-15 8 23 2.9 8 ]0 1.2 15 33 2.0 June 16-30 10 52 5.2 5 0 0 ]5 52 3.5 July 1-12 4 0 0 5 0 0 9 0 0 Total 47 127 2.7 46 37 0.8 93 ]64 1.8 *The vessel and nets used in 1969-1971 differed considerably from those used in 1975

82 "Delaware" in this area and season, England, and might involve smaller and periods of spawning of the bluefin indicate that at least some of the me- fish. tuna, and more extensive tentative ones. dium-sized and the larger "small" blue- Characteristics of the gonads of The best documented spawning fm have spawned in May and June in giant bluefin tuna collected during ex- area is in the Gulf of Mexico (Figure the waters north of the Gulf Stream off ploratory fishing cruises of United 68). Bluefm larvae have been collected the northeastern United States. We have States and Russian research vessels in- over much of the deep (more than 200 noted (Section VC 1) that ripe or nearly dicate that these fish may spawn in the m) area of the Gulfnorth of25°N, and ripe bluefm may have travelled consid- northwestern Caribbeap., the Windward also off the northern edge of the erable distances in short periods before Passage, the old Bahama and Santaren Campeche Bank, near 23°30'N and their capture. In this case, however, Channels, and a large area east and 94°30'W, and at 23° 30'N, 85°W. The Watbne (1959), Wilson and Bartlett north of the Bahamas (Figure 70). Their most thorough and extensive surveys (1967), and all the additional data we presence in numbers in the latter area of the area were carried out in April~ have been able to collect on bluefin during the spawning season is con- May 1973, and May-June 1974 (Juarez tuna catches in the western North At- firmed by catches of the Japanese I974b, Montolio and Juarez 1977). A lantic, indicate that medium-sized blue- longline fishery (Fisheries Agency of few specimens have been collected in fm have occurred north of the Gulf Japan 1971, Wise and Davis 1973). early July, and one, reportedly, in Au- Stream during the winter and spring The collection data and sizes of the gust. The last specimen, a 17.1 mm SL but have been only rarely captured south fish, and their gonad weights and ma- juvenile collected in the northern Gulf of it and west of 600W longitude. It turity indices are shown in Table 25. in August, almost certainly represented. therefore seems unlikely that these fish Zharov (1965) observed that large an aberrant occurrence, or a case of had migrated from southerly areas im- bluefm taken by longline in late May incorrect collection data, since the mediately before their capture. and early June 1963 north of the Baha- northward migration of spent adult blue- Baglin (1976) presented a histo- mas and east of central Florida (near fm through the Straits of Florida ceases gram showing the "gonadal-somatic in- 29°00'N, 79°00'W, and 30000'N, before the end of June (Rivas 1954, dex" (the "gonosomatic relation" of 77°30'W) were "typically spawning, Mather 1963a), and no adults of the Rodrfguez-Roda 1964a) by months for since their sexual products were in species have been recorded in the Gulf 67 bluefm tuna weighing over 100 kg stages IV to VI-II" (these stages were of Mexico in late July or August, to our (Figure 69). The specimens were from not defmed). The fish were from 198to know ledge. These same considerations, various areas, but nearly all of those 238 cm (average 219.4 cm) long, and and the fact that the authors did not list captured in May and June, when the weighed from 140 to 220 kg (average the characters on which they based their index was at its maximum, were from 177.5 kg). larval identification, also cast doubt on the vicinity of Bimini and Cat Cay in The information summarized Gorbunova and Salabarria's (1967) re- the Bahamas. The mean gonadal-so- above defines some positive locations ports of blue fin tuna larvae in the Gulf matic indices were about 1.5 in May and 1.0 in June, as against values of from 0.25 to 0.5 in other months. The sex ratio for 237 large bluefm tuna which had been captured near the Bahamas in the years 1950-1966 and ~ 1.6 examined by Woods Hole Oceano- - 17 graphic Institution and National Ma- ~ 1.4 rine Fisheries Service personnel (un- ~ published data) and Rivas (1954) was (.) 1.2 72% females and 28% males. i:::: . 12 Baglin (1976) also showed the fre- ~ 1.0 - quency distributions of ovum diameters for bluefm taken at various dates ~0.8 and in various conditions. He found no

83 of Mexico in September, and in Cuban adult fish, which has usually occurred of the effects of various conditions, waters in September and October during the last half of June. however, are extremely diversified. (Potthoff and Richards 1970, Richards As noted above, the collections of Among the environmental factors 1976). The major spawning of giant bluefm larvae in the central and west- most frequently considered are the tem- bluefin in the Gulf of Mexico most ern parts of the Straits of Florida off perature, salinity, density, transparency probably takes place in May and June, Miami suggest that spawning may have and oxygen content of the water, winds, with lesser occurrences in late April occurred in the Straits south and west tides, currents, atmospheric pressure, and early July. of there, off the Florida Keys or possi- rainfall, and abundance of plankton. The distribution of catches of lar- bly in the southwestern Gulf of Mexico. Most of this research has centered on val bluefin tuna along the transect of Bluefm tuna have very rarely been ob- mature individuals. Less attention has the Florida Straits from Miami to served off the Florida Keys (Section been paid to the effects of environmen- Bimini, with the largest catches at the IV), but, as Juarez (1974b) pointed out, tal conditions on the hatching of eggs western and central stations, and none the species tends to spawn in offshore and the survival of the early stages. in the station off Bimini, seems very waters. Most of the very large sport With the present decrease in the spawn- significant It suggests that the majority fishing effort exerted off the Florida ing stocks, however, knowledge of these of the larvae have been transported by Keys has taken place on or close to the factors may also be very important. the Florida current from areas in the continental shelf. This might explain southwestern part of the Straits, and the scarcity of observations ofbluefm, 2. Mediterranean Sea possibly even in the southwestern Gulf even if they had been spawning in the Since the ancient trap fisheries in of Mexico. Conversely, it does not in- deep waters off the Keys. the Mediterranean Sea depended on dicate extensive spawning in the area the spawning behavior of the bluefin of the fishery for adult bluefm along tuna, much attention has been paid there the northwestern edge of the Great E. RELATIONSHIPS BETWEEN to the effects of environmental factors Bahama Bank. This in turn strongly ENV]RONMENTALFACTORS on this behavior. supports the belief that the majority of AND SPAWNING BEHAVIOR Roule (1914a, 1914b, 1917), a pio- the large adult bluefm which pass neer in these studies, concluded that Bimini in May and June have spawned 1. Introduction the bluefm tuna was "stenothermic" before arriving there, as did the studies Biologists agree that the spawning and "stenohaline." These beliefs were of their gonads (Rivas 1954, Baglin behavior ofbluefm is strongly affected the basis of his "halo-thermic" theory. 1976). Rivas' (1954) alternative sug- by environmental factors and that its Roule did not specify the limits, or gestion that the northward migration sensitivity to these factors is intensified averages, of the temperatures and sa- might include schools of spent fish, during the reproductive period. Opin- linities which were suitable for the blue- which may take bait, and schools of ions as to the importance and the nature fm. He did, however, note that the sen- ripe fish, which do not, seems less probable in view ofthis new information on the distribution of larvae. It thus appears that this migratory passage off the northwestern Bahamas is actually a spent fish run, analogous to the "re- 5 turn" runs which occurred regularly • ""BERMUDA••• along the north coast of the Thero-Mo- :.' .".: .', .: . roccan Bay and in some Mediterranean ..-- ..... ,,' localities. Rivas (1954), Potthoff and .' Richards (1970), Richards (1976) and , Baglin (1976), on the basis of their ··, studies of gonads, larvae and juveniles · 11 collected in or near the Straits of Florida and the occurrences of spent adults along its eastern edge, reached slightly different conclusions about the probable dates of spawning in that area. All ,- of their estimates, however, fell within (~,...., the months of April, May and June. The total evidence suggests that some /~;.~~t~:.~.~,~-~---'\G spawning may have occurred in late April, but that the bulk of it has taken place in May and June. The termina- Figure 70. CoIlection locations for the large, mature bluefin tuna collected during tion of spawning may weIl have coin- exploratory fishing cruises of United States and Russian research vessels (see cided with the disappearance of the Table 25) ..

84 Table 25. Collection data and sizes oflarge, mature bluefin tuna taken in the area bounded approximately by latitudes 20DNand 33DNand longitudes 69°W and 81oW, with their gonad weights and· maturity indices. Temperatures of the ambient water are shown.

Sample Collection Collection Fish Fish Gonad Index of Water Temperature·C Number- Date Location Length (cm) Weigbt(kg) Weight (kg) Maturity Surface SSm

I IV-12-55 200N 81° W 245.6 (250.5) 11.8 21 2 IV-23-55 1~ 55' N 74° 10'W (227) (195.0) 4.8 41 3 IV-24-55 19°45' N 74° 45' W 223.9 (187.3) 5.5 34 4 IV-27-60 20° 21'N 73° 47' W 203.1 (137.3) 1.5 94 27.2 4 IV-27-60 20° 21' N 73° 47' W 211.9 (157.3) 3.1 51 27.2 4 IV-27-60 . 200 21' N 73° 47' W 214.5 (163.6) 5.3 31 272 4 IV-27-60 20° 21' N 73° 47' W 224.6 (188.6) 5.3 36 27.2 4 IV-27-60 20°21' N 73° 47' W 250.5 (266.8) 6.0 45 27.2 5 IV-23-61 32° 39' N 68° 34' W 244.5 (187.7) 4.8 39 18.6 18.4 6 IV-24-61 300 14' N 69° 17' W 236.5 (221.8) 8.6 26 20.8 19.6 7 IV-25-61 29° 18' N 71° 17' W 213.7 (160.5) 3.4 47 20.8 19.7 7 IV-25-61 2~ 18' N 71° 17' W 214.8 (1632) 3.2 51 20.8 19.7 8 IV-28-61 26° 52' N 76° 10'W 215.3 (164.1) 5.8 28 23.6 22.4 9 IV-29-61 25° 48' N 77° 07' W 218.6 (172.7) 2.8 61 23.6 22.4 00 VI 10 V-15-61 200 06' N 73° 40' W 212 (157.3) 9.2 17 27.9 26.3 II V-17-61 24° 25' N 74° 26' W (204) (139.6) 2.0 68 26.5 25.3 11 V-17-61 24° 25' N 74° 26' W 211.3 (155.5) 5 31 26.5 25.3 12 V-18-61 26°30' N 75° 08' W 203.8 (136.4) 1.6 86 25.5 24.6 12 V-18-61 26°30' N 75° 08' W 208.6 (149.1) 2.3 65 25.5 24.6 12 V-18-61 26°30' N 75° 08' W 209.3 (151.4) 1.8 83 25.5 24.6 12 V-18-61 26°30' N 75° 08' W 213.5 (160.0) 3.4 47 25.5 24.6 13 V-19-61 28° 02' N 76° 34' W 208.5 (149.1) 3.8 40 24.2 20.8 13 V-19-61 28°02' N 76° 34' W 211.0 (154.5) 2.5 62 24.2 20.8 13 V-19-61 28°02'N 76° 34' W 211.8 (156.4) 1.6 98 24.2 20;8 13 V-19-61 28°02' N 76° 34' W 214.1 (161.8) 5.7 28 24.2 20.8 13 V-19-61 28°02' N 76° 34' W 222.7 (183.2) 3.3 56 24.2 20.8 14 V-20-61 27° 39' N 78° 20' W 198.5 (127.7) 6.1 21 25.6 24.1 14 V-20-61 27° 39' N 78° 20' W 209 (150.5) 4.9 31 25.6 24.1 14 V-20-61 27° 39' N 78° 20' W 209 (150.5) 2.5 60 25.6 24.1 15 V-22-61 23°40' N 79° 08' W 213.1 (159.6) 3.0 54 26.7 26.1 15 V-22-61 23° 40' N 79° 08' W 226.5 (193.6) 6.1 32 26.7 26.1 15 V-22-61 23° 40' N 79° 08' W 230.7 (204.6) 6.2 33 26.7 26.1 Sample numbers refer to station locations shown in Figure 70. Figures in parentheses are estimated. sitivity of the fish to these properties of Sella(1927, 1929a, I929b, ]932a, traps off Calabria (southern Italy) and the water were heightened during the 1932b) disputed the almost unanimous Tripolitania, where the water is:warmer period of gonadal maturation. He con- views on the movements and effects of (about 20.8°C - 21.8°e) arid more sa- cluded that, in this period, the bluefin environmental factors by the scientists line, caught mainly small and medium- sought the warmest and most saline who studied the biology of the eastern sized fish. waters of the western Mediterranean. At]antic and Mediterranean bluefin Sella (I927) refuted R.oule's This conclusion is somewhat inconsis- tuna. Most of these supported the views (1924) hypothetical migration of blue- tent with his use of the terms of Pavesi (1887), de Bragan~a (1899), fin tuna along the line of maximum "stenothermic" and "stenohaline." Sanzo, (19 lOa)and Roule (1914a, 1917, thermal increment from off southern In support of his "halo-thermic" 1924). Sella traced migrations of blue- France to off Tunisia. He showed that theory, Roule (1924) showed that the fin tuna by a new method. He collected the tuna taken in the former area aver- direct route from a wintering area for many hooks and lures which had been aged less than 20 kg, whereas those blueftn tuna off the Mediterranean coast found in fish caught in traps. He then taken in the Tunisian traps averaged 70 of France to a spawning area off Tuni- determined the areas where the hooks kg. Sella also differed with Roule sia followed the path of maximum ther- and lures, which were then handmade (l914a) in regard to the influence of mal increment, crossing isotherms of in distinctive local patterns, were in currents. Sella (1932b ) showed that suc- successively higher temperatures at use. His fmdings indicated that several . cessful fishing of the very productive right angles. The isotherms at a depth bluefm tuna had migrated from the At- traps off southwestern Sardinia de- of 10m had been traced during an lantic into the Mediterranean, and that pended on having their leaders reach oceanographic survey made in the others had made extensive migrations beyond the local northeasterly counter- spring of 1923. within that sea. current into the main southwesterly cur- Roule (1924) also studied the rela- Sella also disagreed with Roule's rent, which was farther offshore. This tionship between the bluefm catches of view that the species was absolute]y main current was deflected upward by the trap at Sidi Daoud, Tunisia, and the stenothermic and stenohaline. He the bottom topography, resulting in rainfall in spring at Bizerte, over a 35 pointed out that feeding bluefm tuna colder water at the traps than elsewhere year period. He found that the trap occurred in numbers in many localities in the vicinity. Sella offered the hy- catches generally declined in years of whose waters included a very wide pothesis that the tuna followed this deep heavy rainfall. He attributed this to the range of temperature and salinity. He current from a distant area, and favored decrease in the salinity of the waters agreed with Roule in regard to the in- its water over the local waters with near the trap caused by the increased creased sensitivity to environmental different characteristics. He emphasized outflow of fresh water from the large factors of maturing bluefin tuna, but the importance of studying currents m Lake of Bizerte. He used these two showed that even these fish did not research on the behavior of the species~ examples to demonstrate the seek maxima of temperature and salin- Scordia (1937, 1938, 1942) con~ stenothermic and stenohaline charac- ity. As an example, he pointed out that ducted extensive studies at the traps off teristics of the bluefm. no spawning occurred in the eastern eastern Sicily and Calabria, and also of Roule (1914a, 1917) believed that Mediterranean, where the salinity was the hook and line fishery in thy Strait of the relatively cold waters of the Strait the highest. He supported this state- Messina (Scordia 1932, 1934). She of Gibraltar prevented the passage of ment by pointing out that all of the maintained that density in situ was an any significant numbers ofbluefm tuna, "arrival" traps, whose catch consisted important factor in controlling the particularly during the spawning sea- almost entirely of maturing fish, were movements of spawning bluefm tuna. son when their sensitivity was increased, west of the 38 0/00 isohaline, where She also found that atmospheric de-" from the Atlantic into the Mediterra- the salinity was lower, whereas only pressions and "zoo cun'ents" (currents nean. He therefore strongly supported "return" traps, whose catch consisted containing large quantities of zooplank- Pavesi's (1887) and de Bragan~a's mainly of large spent fish, were east of ton) and water temperature strongly (1899) opinion that the Mediterranean it, where the salinity was higher. He influenced local movements ofmatur- bluefm constituted an autochthonous felt that, instead of maxima, the maturing fish in the vicinity of the traps. A stock, completely independent of the ing bluefin tuna sought specific hydro- requirement for successful fishing of Atlantic bluefm which· spawned very logical conditions. He maintained that the traps in the Tyrrhenian Sea waS the near the Strait of Gibraltar. maturation· occurred in the period of presence of a "hypothermia barrier" of The influence of winds on the the most rapid them1al increment. He water with a temperature of 14°C at movements of the fish near the also showed that the larger maturing depths of 35-40 m. Although she did Sardinian traps was slight, according to bluefm evidently favored somewhat riot believe that bluefin from the Atlan- Roule (I 914a). He concluded from his colder and less saline water than the tic spawned in the Mediterranean, she observations there, however, that in- smaller ones. The important Favignana . concluded (1938) that the arrival creases in the density of the water fa- trap off the western end of Sicily, and ("transgression") of Atlantic current. vored increased catches. Roule (1914a) the group of three equally productive waters was the determining cause of stated that all of the traps for spawning traps off southwestern Sardinia, where the reproductive migration of the blue- bluefm were designed to capture fish the water temperature (about 18.0- fin tuna, and consequently of their en- which were swimming against the fish- 18.8°e) and salinity are relatively low, try into the traps. ]n Scordia's opinion able current. took mainly large maturing fish. The environmental conditions, rather than

86 the state of the gonads, detennined the ferred the cooler waters. Like Sara extended eastward into the Mediterra- movements of the species during the (1964, 1973), he noted that groups of nean Sea or southward to the Canary spawning season. tuna which entered the traps at differ- Is]ands. Sara (1964, 1973) also maintained ent times sought different depths and The immediate purpose of these that the entrance of bluefm tuna into temperatures. There was some ten- investigations was to detennine the en- the traps depended greatly on the posi- dency, however, for the groups to ac- vironment in which the tuna matured tion of the Atlantic currents, which in climate to warmer waters nearer the and presumably spawned, and the ef- turn was influenced by the prevailing surface as their period of confinement fects of the various factors on the spawn- winds before and during the spawning increased. He did not note any relation- ing behavior and related movements of season. He believed, however, that most ship between the occurrences of the the tuna. The ultimate objective was to of the large maturing bluefm taken in bluefm with the salinity, density in situ, improve the fisheries, or at least to per- the traps had followed the Atlantic cur- or transparency of the water. mit better estimates of their potential rent from the ocean into the Mediterra- As noted above, little research on and predictions of their tluctuations. nean. He found that layers of water the important subject of the effects of The effects of the environment on the with temperatures of 16°C to 19°C, at the environment on eggs and early early stages of the bluefin tuna were suitable depths, were most favorable stages ofbluefm tuna has been carried also investigated. for the approach of maturing bluefm out. The difficulty in collecting these Frade and Vile]a (I962) summa- tuna to the traps. The depth of the suit- early stages at the tuna traps led Roule rized the environmental factors consid- able layer varied, in different parts of (1923) to conclude that they were pho- ered by various authors as folIows: western Sicily, from 5 to 25 m. Sara tophobic and occupied abyssal waters. Intrinsic factors: Temperature of the felt that the vertical thickness of the He extended his hypothesis to the pos- water at various depths and 17°C layer was a detennining factor. sible passive transport oflarval bluefin thermoclinal topography, density He agreed with Scordia that the 15°C from the Mediterranean into the Atlan- of the water, salinity, pH, transpar- isotherm, which usually occurred at tic by the deep outtlowing current. Sella ency, currents, etc. depths of 50-60 m in the areas which (l929a) refuted this idea, pointing out he studied, constituted a barrier to the that larval and juvenile bluefin were Extrinsic factors: Air temperature, maturing fish. He further noted that the photophilic and that he had colIected atmospheric pressure, irradiation, bluefin in different groups, usually con- thousands of them at the surface with light intensity, wind, rain, etc. sisting of individuals of the same, or the aid of iights. He believed that, if Other factors considered include nearly the same, size, tended to remain there was any passive transport of early dissolved oxygen and tides (Lozano together in the traps, with each group stages of bluefin through the Strait of Cabo ]957, 1958, 1970) and chloro- staying at a depth where a favorable Gibraltar, it would be from the Atlantic phyll productivity (Rodriguez-Roda environment existed. He believed that to the Mediterranean, with the inflowing ]963). the conditions selected by each group surface current. Sparta (1933) and Sara depended on the conditions in the area (1973) supported Sella's opinion that b. Portugal from which it had come to the trap, and juvenile b1uefm were attracted to light. Don Carlos de Bragan~a, king of the degree of acclimatization it had un- Scaccini et al. (] 975) concluded Portugal, conducted what was prob- dergone during this migration and while that the early stages of the bluefin tuna ably the first methodical study of envi- being held in the trap. Sara also studied could withstand a wide range of hydro- ronmental conditions, the spawning be- the transparency of the water in the logical conditions, even when changes havior of the bluefin tuna, and the vicinity of the traps. He found no rela- occurred rapidly. They believed that an catches of tuna traps in the eastern At- tionship between this factor and the abundant supply offood, consisting of lantic. We have not seen his report (de occurrences of blue fin tuna, despite the zooplankton, was the prime requisite Braganya, ]899) but have found quota- finn belief of the local fishennen that for the survival ofthe larvae and small tions from it, and discussions of its clear water was a prerequisite to their juveniles. contents, in Pavesi (1889), Roule presence. (l9]4b, ]9]7), Parona (1919), F. de Arena (1964) also made detailed 3. Eastern Atlantic Buen (] 925) and other sources. studies of the behavior of bluefin tuna During the fishing season of 1898, a. Distribution, Objectives and in and around the traps, and of related de Braganya colIected hydro]ogical and Nature of Research environmental factors. His research was meteorological data, and attempted to Environmental research related to conducted at traps at Milazzo (Gulf of observe the behavior of the tuna them- the spawning behavior of bluefin tuna Patti, northeastern Sicily) in] 96] -] 962, selves, from his yacht "Amelia" in the in the eastern Atlantic has been inten- and at San Cusumano (near Trapani, Ibero-Moroccan Bay. He also had de- western Sicily) in ]958. He found that sive in the Ibero-Moroccan Bay, espe- tailed data on the catches of the Portu- the fish entered the traps at various ciaIly at the sites of tuna traps, and in guese tuna traps collected concurrently. the Strait of Gibraltar, but sporadic in depths (40 meters to the surface) and in These traps were located in the prov- waters of various temperatures, rang- the remainder of this large area. ince of A]garve on the country's south ing from 15.5 °C to 21.5°C. In general, Some of these studies were of a coast, which forms the northwestern local nature, in the vicinity ofparticu- however, his fmdings supported SeIla's boundary of the Ibero-Moroccan Bay (1929a) view that the larger fish pre- lar traps, but others covered most or all (Figure 44). He examined the com- of the Ibero-Moroccan Bay, or even

87 bined information in an effort to deter- raphy and the tuna fisheries ofthe Ibero- In discussing the results, F. de Suen mine the spawning behavior and the Moroccan Bay (westward to Cape St. (1925) stated that the bluefin tuna was related movements of the tuna, and the Vincent and southward to Casablanca, a typically stenothermic fish, whose influences of environmental factors on Morocco) and the western Mediterra- distribution was exactly limited by tem- them. nean, or Alboran Sea (eastward to Cape perature. In the spawning season, its De Bragan~aconcluded that varia- de Gata, Spain, and the Mulaya River, sensitivity to temperature increased. In tions in meteorological conditions- Morocco) was carried out (F. de Buen his opinion, the tuna was a surface- waves, strength and direction of wind, 1924,1925, 1927;0. de Buen 1924;R. dwelling fish, submerging occasionalIy barometric pressure, and air tempera- de Buen 1927). The most important of to depths of only a few meters; He ture-had no effect on the movements of these reports, from the biological point rejected the abyssal winter habitat pro- the tuna during the trap fishing season of view, is that of F. de Buen (1925). posed by Pavesi (1887) and supported (May-August). He believed that varia- This work was conducted under the by Sanzo (1910a). He believed that the tions in their displacements in this pe- terms of international accords reached adult tuna which inhabited the western riod were caused by changes in the at the meetings of the International Mediterranean basin were altogether marine environment itself, mainly in Commission for the Scientific Explora- independent of those occupying the its temperature. He observed that the tion of the Mediterranean Sea in Paris, adjacent parts of the Atlantic. He pos- bluefm tuna was not found in waters January 11, 1923 (0. de Buen 1924,F. tulated that the colder waters of the with temperatures of less than I3°C, de Buen 1925). Strait of Gibraltar separated the two and believed that the tunas' choice of A general oceanographic survey basins oceanographically and prevented limited areas in the trap fishing and of the area, including 540 operations, the intermingling of these two groups spawning season was explained by was conducted under the direction of of tuna. variations in the temperature of the Dr. O. de Buen on the Spanish naval De Buen concluded, from his own water. transport "Almirante Lobo." A party observations, that the water tempera- He also concluded that the same on the smaller vessel "Principe Alberto ture was the main factor influencing groups of tuna which had passed the de Monaco" concurrently collected bio- the movements of the tuna, and pro- Algarve coast in the "arrival" fishery logical and statistical data from the tuna posed a thermic theory, as opposed to re-appeared there from· 50 to 52 days fisheries in the area. Dr. F. de Buen was the hydrodynamic theory of Bounhiol later inthe "return" fishery. In the mean- in charge of the biological work of the (1911) and the halothermic theory of while, he believed, they had spawned entire campaign. Roule (1914a). in the eastern part of the Ibero-Moroc- To determine the causes of the F. de Buen (1925) found, by com- can Bay, with only insignificant num- arrival of the tuna on the Spanish coasts, paring the Spanish trap catches of May bers of them entering the Mediterra- data were gathered on the winds, the 1923 with oceanographic observations nean. He noted that, although some surface currents, and the transparency made concurrently in the same area, bluefin tuna occurred in Portuguese of the water. F. de Buen (1925) main- that the maturing "arrival" tuna pre- . waters throughout the year, the tained that the general oceanographic ferred the warmer and less saline wa- Algarvian trap fishery was the only one conditions were the unique local causes ters near Cadizto the adjacent colder in which these fish were abundant and of the spawning concentration oftunas and more saline waters, which are typi- folIowed a regular migratory pattern. off the Atlantic coast of southern Spain. cal of the open ocean to the west and Vilela and Pinto (1958) presented Water transparency was a very impor- the Strait of Gibraltar to the east. monthly maximum, minimum and av- tant factor, as was demonstrated by the After the peak ofthe "arrival" fish- erage sea surface temperatures and sa- catches of two traps near the mouth of ery along the coast, the fishery dimin- linities taken near the tuna trap off Cabo the Guadiana River at the Portuguese ished. This coincided with the greatest de Santa Maria, on the southern or border. About 90 percent of the fish intensity of spawning In general, the Algarve coast of Portugal during the were caught in clear water. The re- conditions causing variations in the wa- trap fishing season, from April 24 mainder were taken in "regular" or ter temperature, such as the persistence through August. Although this was not "dirty" water, without a consistent dif- of certain winds and the influence of specified, we presume from the conference between the catches in these coastal currents, were secondary fac- text in which they were presented that two types. The clarity of the water, tors affecting the local movements of these determinations were made in however, seemed more critical during tuna. 1958. They also listed the portion of the "return" (westward) movement than Fresh waters carrying suspended the 1958 catches of the Algarvian traps during the "arrival" (eastward) transit. materials might have caused the tuna to which was used by the canneries (about It was difficult to find a definite rela- leave the coast and temporarily pre- 80 percent of the total) by months in tionship between winds, or wind-driven vented their capture by certain traps. numbers and weight of fish in each of currents, and the catches of the traps. The spawning areas coincided with the the traditional Portuguese size groups. De Buen concluded that the direction, centers of high temperature, varying These data are shown in Table 26. intensity and frequency of the winds constantly under the effect of coastal might act as a secondary factor influ- factors on one side, and the high seas c. Spain encing the local movements ofthe tuna on the other. From April to August 1923, an by altering the temperature of the sur- F. de Suen stated that after spawn- extensive dual survey of the oceanog- face waters. ing, the tuna, no longer subject to such

88 close constraints in regard to tempera- as did the surface temperature, in the of 0.40, with a probable error of +/- ture, dispersed in the Ibero-Moroccan final days. The water was colder at 35 0.10, between the transparency and the Bay, contributing another period of m than at the surface. catch. The best catches occurred at great catches for the traps (the return). Lozano Cabo found a negative cor- transparencies of more than 13 m and The maximum catches in the "return" relation index of -0.29 with a probable especially over 15 m. Minimal catches fishery, however, were concentrated at error of +/-0.11 between the surface always occurred at transparencies of the western and eastern ends of the temperature and the catch. There was less than 14 m. southern Spanish Atlantic coast, at or no correlation between the temperature The fishermen believed firmly that near areas where the temperature and at 35 m and the catch. The "arrival" the catches of the traps depended inti- salinity were considered the least fa- tuna preferred water ternperatures from mately on the lunar phases and the vorable during the "arrival" period. 18°C to 2 I.5°C off southern Spain and tides. Lozano Cabo could not confum O. de Buen (1924), in a prelimi- Morocco, with a more specific prefer- this, except that, when tuna were nary report on this survey, presented ence for 18.2°C to 18.7°C at Barbate. present, they tended to enter the trap the following conclusions: The transparency of the water, with rising tides. This might signify a The moment of spawning changed measured by Secchi disc, varied from 5 negative rheotaxis, at least during their from year to year according to changes m to 17 m, with a mean of 13.04 m, at pre-spawning migration. The correla- in environment. Barbate. There was a correlation index tion coefficient of +0.10 with a prob- Increases and decreases in water temperature exercised a great influence on the development of the gonads. High temperature, high salinity and Table 26. Surface temperatures and salinities at the trap off Cabo de Santa Maria agitated waters with high dissolved oxy- and catches of the traps in the Algarve (southern Portugal) in the period from late gen content were sought by the tuna for April through August by month. spawning. The temperature of the surface wa- TEMPERATURE AND SALINITY OF THE ter in the Strait of Gibraltar was 3°C SURFACE WATER OFF CABO DE SANTAMARIA lower than that of the coast of Cadiz, and 5°C less than that of the Mediterra- Temperature eC) Salinity e/oo) nean coast of Morocco from Ceuta east- Month Min. Max. Avg. Min. Max. Avg. ward. These conditions were unfavorable for spawning tuna, and constituted April" 15.0 19.5 17.4 35.93 36.02 35.97 an obstruction to their migration through the Strait. On the other hand, May 15.0 20.5 17.3 35.77 36.15 35.99 the currents and winds in the Strait June 15.0 20.0 17.4 35.77 36.22 35.96 increased the dissolved oxygen in its July 15.5 20.0 18.7 35.82 36.11 35.96 waters, a favorable factor for such mi- August 17.0 26.0 22.3 35.73 36.29 36.04 grations. The tuna spawned west of Gibraltar FISW RECEIVED BY THE CANNERIES. before reaching Tarifa, where the salinity became lower. 1958 "Atuns" "Atuarros" 'Albacoras' "'Cachorretas" Total The next important survey of the environment in relation to the occur- May Weight kg 73,166 8,713 723 115 82,717 rences of spawning bluefin tuna in No. offish 439 119 12 7 577 Spanish waters was by Lozano Cabo (1957, 1958). He studied oceanographic Average kg 166.7 73.2 60.3 16.4 143.4 conditions at the Barbate trap east of June Weight kg 307,071 130,658 3,052 500 441,291 Cadiz and the biology of its catches No. offish 2,330 1,903 68 78 4,379 during the 1954 fishing season. He Average kg 131.8 68.7 44.9 6.4 100.8 made similar studies in the Moroccan trap fishery (Section VE3d) in 1954, July Weight kg 65,870 4,746 244 70,860 providing the basis for interesting com- No. offish 457 64 5 526 parisons of data from the two areas. Average kg 144.1 74.2 48.8 134.7 The surface temperature at Barbate August Weight kg 21,282 1149 932 23,363 in June and July varied from 17°C to No. offish 157 15 17 189 2 I°C (I 8.9° +/-0.089°), increasing progressively despite small local alter- Average kg 135.6 76.6 54.8 123.6 ations. There were greater fluctuations, from 14°C to 19°C (16.83° +/-0.146°), "April 24 - 30 in the temperature at a depth of 35 m, bSize groups of fish (Vilela 1960): Atuns> 90 kg, Atuarros = 50 - 89 kg, which decreased, instead of increasing Albacoras = 30 - 49 kg, Cachorreta:s <30 kg.

89 able error of +1-0.12 between the state ing the 1969 arrival run were taken in a oceanography and the plankton in gen- of the tide and the catch of Barb ate was week with mean temperatures of about eral, could be said to be under the influ- not significant. 18°C at the surface and 16°C at 30 m. ence of Atlantic waters, especially in Salinities and dissolved oxygen During the "return" period in July and its surface layers. were also observed at Barbate by August 1968,the best catches took place Lozano Cabo. Although measurements with temperatures of 19.5°C to 19.9°C d.Morocco of both were taken from the surface at the surface and 16.3°C at 30 m. In Lozano Cabo (1957, 1958, 1970) and at depths of30 m or 35 m, he did 1969, the best "return" catches were conducted thorough studies of the en- not study the correlation with the taken with mean surface temperatures vironment at the Los Cenizosos trap, catches. He had found no correlation of21.0°C to 22.5°C, and temperatures north of Larache, Morocco. Our ac- between salinity and catch at the Los of 18.5°C to 20.2°C at 30 m. Rodriguez- count generally follows his 1970 sum- Cenizosos trap in Morocco. Salinities Roda noted (I969a), that the August mary, with some details added from at Barbate fluctuated between 35.39 01 temperatures in 1961, 1962 and 1967 the earlier reports. The water temperature varied from 00 and 35.53 0/00 at 35 m. Dissolved were about the same, and that the total oxygen levels were abnormally high production of the Spanish Atlantic traps 17°C to noc at the surface, from 15°C varying from 6.9 to 8.1 ccll at the sur- in those years did not vary greatly. In to 20°C at 15 m, and from 14°C to face and 5.0 to 9.0 ccll at 30 m. his 1970b publication, he observed that 18°C at 35 m. The correlation between Rodriguez-Roda (I 963, 1965, the catch of these traps was greater in the surface temperature and the num- 1969c, 1970a, 1970b) collected envi- 1969, when the water was warmer, than bers offish caught was negative (-0.72 ronmental data at the Barbate trap from in 1968. Rodriguez-Roda (1971) con- +1-0.06). Fish were caught at tempera- 1961 to 1969, and discussed their pos- cluded that the maturing "arrival" pe- tures between 17°C and 21°C, but sible relationships to its catches and the riod begins at temperatures of 16°C to mainly between 18°C and 19.7°C. movements of the maturing and post- 17°C, and is most productive at tem- The transparency of the water spawning bluefm tuna. His 1963 publi- peratures of 18°C in the upper 10 ranged from 8 m to 19 m, with an cation presented monthly values of the meters, l7°C at 20 m and 16°C at 30 m. average value of 13.7 m. A high posi- temperatures, phosphate production, In the post-spawning "return" period, tive correlation, +0.59 +1-0.08, existed and salinity, of the water at various optimum temperatures are 20°C to 21°C between the transparency and the num- depths from the surface to 30 m, and its in the upper 10 m and 19°C at 30 m. bers of fish caught in the trap. The transparency and optical absorption. The average salinities during the catches were poor when the transpar- Rodriguez-Roda (I969c) pre- months of May, June and July in 1961 ency was less than 13m and good sented the mean temperatures at 10m and 1962 varied from 35.88 0/00 to when it was over 15 m, especially at 15 intervals from the surface to 30 m in 36.340/00 at the surface and 36.01 01 mtol6m. The salinities were between 36.00 the Barbate trap in August 1967. 00 to 36.21 0/00 at 30 m (Rodriguez- Rodriguez-Roda (1970a) collected daily Roda 1963). 0/00 and 36.34 0/00 at the surface, temperature measurements of the wa- The transparency of the water 36.11 0/00 and 36.33 0/00 at 15m, and ter temperature at 10m intervals from ranged from 11m to 21 m in May and 36.060/00 and 36.25 0/00 at 35 m. The the surface to 30 m for the months of June of 1961 and 1962, and from 2 m correlation between surface salinity and May through August 1968. He com- to 25 m in May-August 1969, the numbers of tuna caught in thetrap,- pared the weekly averages of these tem- (Rodriguez-Roda 1963, I970b). The 0.078 +1-0.13, was not significant. peratures graphically with the corre- author found a high positive correla- Likewise, no correlation was found sponding numbers of tuna caught in tion, during intensive periods of the between the height of the tide (above the trap. He (I 970b ) collected corre- fishery, between the transparency and the daily low water level) and the num- sponding data and presented a similar the catches of the trap. ber of tuna caught, even though the graphical comparison for the same pe- Phosphate production in May, June captains thought that the tides strongly riod in 1969. In that year he also mea- and July, the months of maximum tuna influenced the catches. There was a sured the transparency of the water each catches, varied from 0.54 to 0.59 mg/I clear relationship, however, between day, and he compared these values at the surface. the velocity of the tidal currents and the graphically with the daily catch of the Chlorophyll production was gen- presence of tuna. Good catches coin- trap in numbers of tuna. erally greater in the cold months than cided with tides of large amplitude, The temperature during the most the warm ones, with a large maximum during which the coastal currents were productive months, May to July in 1961 in October and lesser ones in January stronger and farther from shore. and 1962, ranged from 18.0°C to and April. The dissolved oxygen content var- 21.4°C at the surface and 16.5°Cto 18° Zooplankton was predominant in ied from 5.9 to 7.9 ccll at the surface C at a depth of 30 m. During the "ar- the warm months, although undergo- from 5.7 to 7.9 ccll at 15 m, and fro~ rival" run in May and June 1968, the ing many variations during the year, 5.5 to 7.7 ccll at 30 m. highest catches occurred with mean due to the influences of Atlantic wa- Aloncle (1964, 1969) developed a surface temperatures of 17.2°C to ters. hypothesis on the migrations and 18.9°C and temperatures of 16.6°C to Rodriguez-Roda (1963) concluded spawning of bluefin tuna, and the in- 17.6°C at 30 m. The best catches dur- that the Barbate area, in regard to its fluences of water temperature upon

90 them, in the waters between the south- servations which were made concur- ditions of wind and current, however, ern Iberian coasts and the Canary Is- rently with investigations, but have not and it is presumed that they must spend lands. This hypothesis was derived from been synthesized or analyzed, and data much of the migrating period at deeper studies of the tunas and their fisheries in atlases or survey reports. levels. A male with milt was taken by off the Atlantic coast of Morocco, and longline at an estimated depth of 55 m a hydrographic survey of the above b. GulfofMexico on the eastern side of the Straits just The best documented spawning of waters. In early June 1964, tuna were north of Bimini (Mather and Bartlett bluefm in the western Atlantic takes found between Lanzerote Island (Ca- 1962). The water temperature at the place in the Gulf of Mexico in from naries) and the African coast in water location was 26.7°C at the surface and late April to early July (Section VD3). with a temperature of 20.06°C and sa- 25.7°C at 55 m. The salinity in the The heaviest concentrations of larvae linity of 36.40 0100 at the surface, and upper 50 m layer in this region ranges evidently occur in the deep (more than 18.37°C and 36.56 0/00 at a depth of from 35.5 0/00 to 37 0/00, with an 200 m) area between latitudes 23°N 50 m. Aloncle believed that these tuna average of about 36.2 0/00, from April 0 were pushed northward with the sea- and 30 N and longitudes 84°W and through June 1977. The average phos- 94°W (Figure 68) (Juarez I974b, sonal warming of the water, and kept phate and oxygen levels in this period Montolio and Juarez 1977). During away from the Moroccan coast by iso- were about 0.1 and 4.65 ppm, respec- therms of temperatures greater than April, May and June the surface tem- tively. 21°C. In the course of this movement, perature of these waters increases from between 22°C and 24°C to a little over he believed that they spawned in the d. East and North oCthe Bahamas area between Lanzerote, Conception 27°C (Galtsoff 1954). The temperature In the waters east of the Bahamas Bank and the Moroccan coast. in the upper layer is fairly constant down to 30 m. The salinity in the upper the research vessel Crawford caught e. Other Eastern Atlantic 50 m layer is typically 36.00 0100. In bluefin with maturity indices from 28 Areas contrast, the salinity of this layer over to 126 (mostly 60-90) at severalloca- The only other parts of the eastern the Campeche and Florida Banks, tions in May 1961 (Figure 70, Table Atlantic where bluefin tuna are believed where few larvae have been collected, 25). The surface water temperatures to spawn are in the vicinity of the A:mres is 36.25 0/00, possibly because of up- ranged from 23.6°C to 26.5°C, but most (Ferreira 1932) and in equatorial wa- welling. of the fish were taken in waters of ters south of Sierra Leone (Richards 25°C. At 55 m the temperature range 1969, Richards and Simmons 1971, c. Straits of Florida was 22.4°C to 25.3°C, but most of the unpublished data reports for Geronimo The Straits of Florida at the Mi- fish were taken where the temperature cruises 3, 4 and 5). ami-Bimini line present an unusual situ- was about 24°C. In May and June, the months in ation in that adult bluefm are found in A little north of the Bahamas the which bluefin reportedly spawn around numbers, and almost exclusively, on Cra~ord caught eight fish with matu- the Azores, the surface temperature in the eastern (Bahamas) side (Section rity indices of 21 to 98 (Table 25) in the area varies between about 17.0°C IVC2), but the abundance of larvae is water with surface temperature between and about 19.7°C, while the salinity minimal on the eastern side and maxi- 24.2°C and 25.6°C and temperature at mum near the Florida side (Section remains at about 36.1 0100. 55 m between 20.8°C and 24.1°C. In the area bounded by latitudes VD3). Most of the fish examined at Zahrov (1965) reported that spawning 7°N and 80S, and longitudes 13oW and Bimini were spent, with a very few ripe fish caught north of the Bahamas (Fig- 15°W, three larval T. thynnus thynnus ones among them (Rivas 1954). Evi- ure 70) at the end of May and the were collected in March 1963, in wa- dently most of the spawning occurs beginning of June were in water with ters with surface temperatures exceed- south ofthis line. surface temperature of 25°C to 26.4°C. ing 27°C and surface salinities of from The surface water temperature across the Straits of Florida between e. Northeastern United States 36.4 0100 to 38.8 0100 (Richards 1969). These temperatures are much higher Miami and the Florida Keys and the The bluefin showing signs of than those in other reported spawning Bahamas (25°N to 26°N and 79°W to spawning taken by the M/V De/aware areas of the species in the eastern At- 80°W) is fairly uniform in the deeper about 500 km off southern New Jersey lantic and the Mediterranean. central area. On the edges of the Strait and the Delmarva Peninsula during where the bottom rises sharply tem- cruise 57-5 (Section VD3) were gener- 4. Western Atlantic peratures are cooler (Sverdrup et al. ally in cooler waters than were any of 1942). The surface temperature in the the previous fish. These catches were a. Introduction deep water is about 26°C to 26.5°C in made in waters of surface temperatures In comparison with what is avail- April, increasing to about 27°C in May between 18.3°C and 25.soC. The most able for the eastern Atlantic and the and about 28°C in June (Pyle 1962). successful catches were in water with a Mediterranean, very little has been pub- Nearly all of the catches ofbluefin temperature around 20°C or 21°C. Fish- lished on the relationships between the tuna in the Straits of Florida have been ing depths were estimated to be 52 m to spawning of blue fin tuna in the western taken by rod and reel from schools 57 m and most of the fish were taken Atlantic and environmental conditions. traveling close to the surface (Rivas where the water temperature at this Therefore our discussion of this corre- 1978). The fish are seen near the sur- depth ranged from 15.5°C to 21.1 °C. lation depends almost entirely on ob- face in this area only under certain con-

91 F. Feeding Activity During the authors have reported observations of of the fish in the school at the same Spawning Season food in the stomachs of maturing blue- time. This causes an enormous bright Different opinions have been ex- fin caught off eastern Sicily (Genovese flash under the surface, with a very pressed in regard to the feeding activity 1960, Genovese and Alonzo 1961 Li spectacular effect. The school, which of bluefm tuna during the spawning Greci 1961). ' usuall y trave Is at from 2 to 7 knots (3.7 season. Many of the studies used indi- The considerable longline catches to 1~ k1~lhr), leaves a rather milky trail viduals caught in traps. It has been of bluefin tuna in the central Mediter- behmd It, due to the emission of sexual argued that the lack offood in the stom- ranean during the spawning seasons of products. achs of "arrival" fish might have been 1973 and 1974 (Fisheries Agency of caused by digestion while the fish were Japan 1975, 1976) prove that signifi- H. Maturity and Fecundity The ages at which bluefin tuna awaiting removal from the trap, or by cant numbers of these fish feed during spawn, and the variation in the fecun- regurgitation resulting from their the spawning season. As Sara (1973) dity offemales with their size and age, struggles during this removal. Food is noted, the trophic (feeding) tendency are two elements of the biology of the frequently found in the stomachs of may on occasion overcome the tenden- species which are especially important "return" fish, however, even though cies which are usually dominant dur- for the management of its fisheries. they undergo the same treatment. ing the spawning period, including the F. de Buen (1925) and Sella tendency to reduce, and fmally stop 1. Age and Size at First (1929a) were of the opinion that the ~eeding as the volume of the gonad~ Maturity: blu~fm continued to feed during their Increases. Research on bluefm tuna in the penod of maturation and spawning, but eastern Atlantic and Mediterranean in- G. The Spawning Act at a reduced rate. De Buen believed dicated that they first spawned at ages The only published accounts of that they ate food which they happened 2-4 (lengths of about 75-125 cm the actual spawning of bluefin tuna to encounter, and could catch without weights of about 12-40 kg). Sell~ which we have encountered described undue effort, but seldom exerted them- (~929a, 1929b) reported that the spe- occurrences in the central Mediter- selves in the pursuit of difficult prey. cies us~ally spawned first at age-3, or ranean. Some of these activities oc- Rodriguez- Roda (1963, 1964a, at a weight of about 15 kg. He added curred while the fish were being held in 1969) found that stomachs oftuna taken that a few age-2 fish which had at- traps, but others, probably more im- in the Spanish "arrival" traps were usu- tained weights of 12 kg through rapid portant because the fish were under no ally empty. Some contained a few growth might also spawn. constraint, took place in the open sea. swimming crabs, Polybius henslowi Frade and Mana<;as (1933) found Sella (1911) and Heldt (1932) de- Leach, which they had presumably con- that young bluefin 1 m long taken in scribed the spawning actions of fish in sumed before entering the trap. Small the "arrival" (May-June) fishery off traps off Sicily and Tunisia on the basis f~h which had been caught in traps southern Portugal developed differently of accounts which they considered reli- With the tunas were occasionally found according to their sex: the males were able. Sara (1964) personally observed in their stomachs. He emphasized the in. active or completed spermatogen- the reproductive acts of tunas in the limitations of his fmdings because of eSIS, whereas the females were in a vicinity of traps off Sicily. Arena (1964) the possible losses of stomach contents very retarded ovogenesis. Arena (1964)· likewise witnessed the spawning of of trapped fish mentioned above. and Sara (1973) have observed that bluefin tuna in the open sea off Sicily. Sara's (1964, 1973) studies of bluefin tuna school by size even dur- These accounts show that spawn- stomach contents of "arrival" fish taken ing the spawning season, a~d that fering occurs at the instant when a pair of in the traps off western Sicily and ob- tilization is accomplished by paired fish turn on their sides and make con- servations of their behavior when con- emissions within these schools. There- tact, or appear to, with their ventral fmed in the traps with species on which fore the reported difference in the times surfaces. This refutes the previous sup- they normally fed, led him to believe of maturity of 3-year-old males and position (Tiews 1963) that tuna that maturing bluefm tuna abstained females implies that their spawning ef- spawned by saturating an area with from eating. He found increasing forts might be ineffective. Rodriguez- randomly discharged eggs and milt. amounts of food in the stomachs of Roda (1929a) concluded from his fe- Arena and Sara, however, reported post-spawning fish, however, as the cundity studies that females attained that small groups of tuna sometimes season advanced and their gonads be- their frrst maturity at a length of about engaged in communal mating. In a spec- came smaller. 97.5 cm, and males at about 105 cm tacular observation, Arena (1964) saw Arena (1964) found stomachs of corresponding to ages of3 years. Frad~ files of 10-12 giant fish overtake other "arrival" fish caught in the western Si- and Vilela (1962) concluded that first files of about the same number, with cilian traps to be empty, or nearly so. matur.ity usually occurred at age 3, but the fish of one file mating with those of Those of others caught off the eastern occasIOnally at ages 2 or 4. the other as they passed. part of the island, however contained Scaccini et al. 1975) reported the P. Arena (personal communica- considerable quantities off~od. A large smallest mature bluefin tuna observed tion) provided the followino- informa- quantity of swimming crabs, Polybius . 0 ?y any ofthem was an individual weigh- tlon on spawning, based on his more henslowiLeach, was found in the stom- Illg ,27 kg (4 years old) examined by ~ecent observations. The mating offish ach of the first group of bluefin tuna Sara at the Solanto trap in Sicily in IIIlarge schools may involve nearly all caught at Milazzo in 1961. Several other mid-June 1959.

92 Less infonnation is available on We believe that the mature mem- In the size range studied, the esti- the age of first spawning of western bers of the "small" bluefm group (less mated fecundity was thus roughly pro- Atlantic bluefin, but these fish have than 120 cm long) spawn in offshore portional to the weight of the fish, or apparently been less precocious than waters north of the Gulf Stream, along the third power of its length. their eastern Atlantic and Mediterra- with fish of the "medium" size group, Baglin (1976), studying six blue- nean counterparts. in May and June. As noted in Section fm tuna taken near Bimini and Cat Cay Westman and Neville (1942) ex- VD3, a few small bluefm and several in the northwestern Bahamas in May amined many small and medium sized medium sized ones taken by longline and June and ranging from 222.5 cm in bluefin tuna landed by the coastal sport in this area and season were examined. length and 188.4 kg in weight to 260.6 fishery at Freeport, Long Island, New The results of macroscopic examina- cm in length and 271.5 kg in weight, York. They reported that nearly all of tions of their gonads were as follows: found that their estimated fecundity in- the "school tuna" (fish averaging less Age III. Two fish were examined. Both creased from 16.7 x 106 for the smallest than 30 kg) were immature. They found were classified as immature. to 31.4 x 106 for the largest. The maxi- some evidence of approaching matu- Age 4. Three males and three females mum, however, was 33.0 x 106 for an rity in a few tuna of the 3-year-old age were examined. One fish of each sex individual 240.8 cm long and weigh- group, and signs of maturity in a larger showed defmite signs of maturity. ing 247.4 kg. Where F is the estimated percentage ofthe4-year-olds. They con- Age 5. One male was examined. Some fecundity, L is the length of the fish in sidered all of the fish of both sexes milt was squeezed from its testes. cm, W is its live weight in kg, and WI is which were 5 years old (about 130 cm Age 6. Twelve fish (six of each sex) the dry weight in g of all of the eggs long and weighing about 40 kg) or 143.5-157 cm long and probably of from both of its ovaries, Baglin calcu- older to be adults, but found no indica- this age were examined. Two of the lated that: tions of eggs or sperm in their gonads. females were classified as spent. The F = 65.4214 U35326 The present authors have con- other ten fish appeared to be ap- ducted macroscopic examinations of proaching spawning condition. F = 6,245,010 + 95,132.3 W the gonads of numerous small bluefm We conclude tentatively from all tuna caught in traps or by sport fishing of these data that the first spawning of F=3,051,104+ 18,916.4 WI' in southern New England coastal wa- bluefin tuna in the eastern Atlantic oc- He concluded that fecundity increased ters and by purse seines in coastal wa- curs at age 3, in exceptional cases, and with size of fish in the length range ters between southern New Jersey and more frequently at age 4. By age 6 all, from 222.5 cm and to 260.6 cm, and New England in the summers of 1950- or nearly all, of the fish are spawners. that, therefore, larger fish contribute 1975. We concur with Westman and Probably the first spawning of western more to the reproductive potential. Neville's conclUsions. We found signs Atlantic bluefin tuna occurs most fre- No significant difference in the of maturity in less than I% of the 3- quently at age 5, but more research is slopes or adjusted means was found by year old fish but in a considerably larger required to establish this. Baglin in a covariance analysis between percentage of the tuna of age group 4. the fecundity-length and the fecundity- Nearly all age 3 fish, like all the 0, I, 2. Fecundity weight relationships found in his study and 2 year-old individuals examined, Rodriguez-Roda (1967a) found of western Atlantic bluefm tuna and had very small gonads which were al- that the estimated fecundity of bluefin those found by Rodriguez-Roda most uniformly slender throughout their tuna caught near Cadiz, Spain, in May (1967a) for eastern Atlantic individu- length, like very flat shoestrings. The and June generally increased with size als. Baglin noted, however, that the 6 gonads of the older fish which were offish, from 5.2 x 10 for an individual samples were small, and that more ex- considered to show signs of maturity 130.5 cm long and weighing 54 kg to tensive studies might reveal significant 6 were distinctly enlarged for at least part 32.2 X 10 for one 230 cm long and differences. of their length. The testes ofa few age weighing 235 kg The minima and The studies of Rodriguez-Roda 6 4 males taken in Cape Cod Bay, Mas- maxima, however, were 5.0 x 10 for a (1967a) and Baglin (1976) indicate sachusetts, in early July 1953, contained fish 160 cm long and weighing 96 kg, clearly that the fecundity of Atlantic 6 milt. Those of a 4-year-old specimen, and 45.9 x 10 forone214 cm long and bluefin tuna increases with size offish, 110 cm long and weighing 25 kg, weighing 191 kg. He calculated the in both the eastern and western parts of weighed 27.5 g and contained milt. A following relationships between F, the the Ocean. Baglin's study shows that photomicrograph (970x) taken by R. F. fecundity or number of maturing eggs, this relationship extends to the very Vaccaro, an Associate Scientist of and (1) L, the length of the fish in cm; large size of 260 em. Pending actual Woods Hole Oceanographic Institution, (2) and (3) PI' the weight of the fish in determinations of the fecundity of larger kg; and (4) P , the weight of the ovaries showed that this milt contained fully 2 fish, there is no reason to suppose that developed spenn. The gonads of most in kg: the fecundity does not also increase of the 5-year-old tuna (about 133 cm (1) F = 2.29245 U with size of fish for the relatively few long and weighing about 45 kg) were (2) F = 53,451 PI 1159489 larger individuals which are captured. generally better developed, and most Baglin and Rivas (l977) estimated the of these fish had probably spawned. (3) F = -1,220,717 + 138,068 PI fecundity of 17-year-old Atlantic blue- (4) F = 553 P 1.337073 6 2 fin as 44.6 x 10 eggs.

93 3. Maximum Size at which tainties over identifications, there is no spawning of bluefin tuna inthe Mediter- Bluefin Tuna Spawn doubt that young stages of blue fin have ranean is most intense in its south-cen- The only authors who have dis- been collected in great numbers in the tral part, but also extends into the west- cussed the largest size or age at which south central Mediterranean. It is un- em Mediterranean and the Adriatic Sea.. bluefm tuna spawn, to our knowledge, fortunate, as noted by Heldt (1930) and As Scaccini et al. (1975) concluded, are Scaccini et al. (1975). They state Dieuzeide (1951), that Sella did not additional research will probably show that the species spawns "up to the maxi- describe the "thousands" of early stages that bluefin spawn in other parts of the mum weight and the maximum age" of bluefm which he (1929a) reported Mediterranean. Some spawning must and cite Sara's observation of bluefm that he had collected. His 1924 pub- also occur in the Black Sea. The ab- tuna estimated to be about 18 years old lication, however, convinced Richards sence of a commercial fishery for the and weighing up to 600 kg, caught in (1976) of the accuracy of his identi- species there, however, and the rela- the trap at Favignana (Aegades Islands, fications. Scaccini (1961, 1968) and tively small catches taken in its ap- just west of the western end of Sicily) Scaccini et al. (1975), to whom Sella's proaches, the Bosphorus and the Sea of in June 1974, as the largest individuals material was available, also agreed with Marmara, suggest that the reproduc- in spawning condition which had been these identifications. The most numer- tion there is not comparable, quantita- examined by any of them. Since the ous collections have been made in the tively, to that in the central Mediterra- number of recorded catches of bluefm Strait of Messina and in waters north nean. tuna weighing over 600 kg is negli- and west of Sicily (Sanzo 1932, Sella gible, it is most unlikely that any sig- 1924, 1929a; Sparta 1933, Scaccini 2. Eastern Atlantic nificant number of these fish attain a 1968, Piccinetti and Piccinetti Manfrin The situation in the eastern Atlan- tic is dramatically different from that in size at which they cease to spawn. 1970, Scaccini et al. 1975). The de- the Mediterranean and Black Seas. De- tailed study of Duclerc et al. (1973) I. Discussion and Conclusions spite extensive research efforts over showed that larval bluefin also occurred A discussion and a presentation of many decades, no identifiable early around the Balearic Islands. Dieuzeide our tentative conclusions seem appro- stages of blue fin have been collected in (1951) described three larval bluefm priate, since much of the information the Ibero-Moroccan Bay, which has collected off Algeria, and Piccinetti in this section is inconclusive and, in been regarded as the prime spawning (1973) and Piccinetti et al. (197 6b) pre- many instances, even contradictory. ground in the region, or in the more sented preliminary reports on occur- recently suggested areas of reproduc- rences of early stages in the Adriatic 1. Mediterranean and Black tion off Morocco and in the Bay of Seas Sea. Biscay. The only identified early stages The Mediterranean and Black Seas Several authors (V odyanitskii from the eastern Atlantic were collected have traditionally been regarded as 1936, Vodyanitskii and Kazanova near the Equator between longitudes prime spawning grounds for the blue- 1954, Oven 1959) have reported on 0° and 15°30'W (Richards 1969, fm tuna. Despite a preponderance of eggs and larvae of blue fin collected in Richards and Simmons 1971). This was scientific opinion against this concept the Black Sea, but have not produced a totally unexpected area on the basis which developed in the last quarter of detailed descriptions. The difficulties of existing knowledge of the distribu- the nineteenth century and the first quar- of identifying eggs and small larvae of tion of maturing bluefin. It certainly ter of the twentieth, it still appears to be bluefin, even after hatching the eggs merits further investigation to deter- valid. The information now available, and rearing the larvae, have been fully mine the seasonal and areal extent of however, indicates that the principal explained by Duclerc et al. (1973) and the occurrence, and also to make cer- reproduction of the eastern Atlantic and Scaccini et al. (1975). tain that the larvae are actually those of Mediterranean bluefin takes place in The regular occurrences of great T. thynnus thynnus rather than those of the south central Mediterranean, instead numbers of maturing bluefin along the T maccoyii, which also occurs in the of occurring in the Black Sea as coasts of western Sardinia, Tunisia and South Atlantic. Aristotle and his followers supposed. Tripolitania suggest that spawning oc- Regular seasonal occurrences of Small juvenile bluefm were first curs in those areas as well. Although very numerous maturing and spent blue- reported from the Mediterranean by the traps on the eastern (Ionian Sea) fin in the Ibero-Moroccan Bay have d'Amico (1816). The eggs and larvae coast of Sicily were known as "return" been abundantly documented. Small were first described briefly by Sanzo in traps, some maturing individuals were numbers of maturing or ripe bluefm in his 1910b publication, and more com- caught in them, along with the more the Bay of Biscay have been reported pletely in his 1929 and 1932 works. numerous spent fish (Sella 1929a, occasionally (Creac'h 1952, Le Gall Some authors have stated that the char- Scordia 1938). Scordia's extensive stud- 1952) and detailed studies of the go- acters presented by Sanzo do not dif- ies (summarized in her 1938 and 1942 nads of a few individuals have just ferentiate the eggs and very small lar- publications) indicated that large num- become available (Cort etal. 1976, Cort vae of blue fin from those of other tuna- bers of blue fin tuna passed through the 1977). The occurrence' of small num- like fishes, especially A uxis. Strait of Messina from the Tyrrhenian bers of mature bluefin at the Azores Ehrenbaum's tentative identifications Sea to the Ionian Sea, spawned there, has been reported (Ferreira 1932), but oflarval T. thynnus thynnus have been and then returned through the Strait to no details on their gonad condition were questioned by Sella (1929a) and the Tyrrhenian. It appears that the presented. Richards (1976). Despite these uncer-

94 3. Western North Atlantic northern edge of the Gulf Stream. or Other collections of larvae al.: The western North Atlantic is the the Gulf Stream front, north oflatitude though less importaiIt than those from only part of that ocean from which 37°N and east of longitude 70° W. the Gulf of Mexico and the central extensive collections of early stages of Mediterranean, indicate that bluefin T. thynnus thynnus have been obtained. 4. Overall Situation spawn around the Balearic Islands in The most important occurrence docu- On the most positive evidence the Black Sea, in the Straits of Flo;ida available, the occurrence of larvae and mented up to now has been in the Gulf and, probably, north of the Bahamas. very small juveniles, one can only con- of Mexico. Bluefin larvae and small Studies of the maturity of gonads juveniles have been collected over ~Iude that the most important spawn- suggest spawning over more extensive 109 areas of are in much of the deep (more than 300 m) T. thynnus thynnus areas .. These would include major part of the Gulf, especially in the area the south central Mediterranean Sea spawnmg along the coasts of Tunisia and the Gulf of Mexico. This in itself is north of latitude 23°N (Juarez 1972 and Tripolitania, and in the !bero-Mo- an interesting parallel, as the Gulf of 1974b;Richards 1976, 1977;Montoli~ roccan Bay (by the fish which do not Mexico and the Caribbean Sea are of- and Juarez 1977, T.e. Potthoff, per- enter t~e !"1editerranean to spawn). ten referred to as the" American Medi- son~1 communication). Important col- ~p~wnIOg m the Bay of Biscay is also lections have also been made in the terranean." mdlcated but this is probably less im- Straits of Florida, particularly at the .. The major spawning occurs ear- portant. Gonad studies in the western Dry Tortugus and off Miami (Potthoff her 10 the western Atlantic (probably Atlantic suggest, extensive additional and Richards 1970. Richards 1976, T.e. about May 15-June 15) than in the spawning areas off Cuba, the Baha- Potthoff. personal communications). Mediterranean (about June 15-July 15). mas, and the southeastern United States Scattered individuals have been col- The smaller bluefin spawn later along the Gulf Stream front north and lected off the east coast of the United than the larger ones in the Mediterra- east of Cape Hatteras. States up to latitude 38°45'N. These nean, and probably do in the western Juarez (l974b) and Montolio and Atlantic also. Studies of spawning in collections show that the Gulf of J.wirez(1977) provided quantitative es- Mexico is the most important bluefin both areas ~ave centered on the larger timates of the numbers of bluefm lar- fish. Some lOformation is available on tuna spawning ground yet discovered vae in extensive areas of the Gulf of the spawning of the smaller individuals in the ~tlantic, ~d that spawning also Mexico. Richards (1976) estimated the occurs m the Straits of Florida and prob- in the M~diterranean, where they mix number of fish in the spawning stock ably for ail unknown distance farther to a cons~derable extent with the larger from the estimated number of larvae north. ones durmg the spawning season. The (Juarez 1974b). His figure was in rea- The condition of gonads of cap- two g~oups evidently reproduce sepa- sonable agreement with those calcu- tured fish suggests that spawning may rately mthe western Atlantic and much lated by other methods. also take place in the northwestern Car- less is known about the sp~wning of No quantitative estimates of the ibbean, the Windward Passage, the Old the smaller fish (all of the "medium" abundance of blue fin tuna larvae in the size group, and the mature members of Bahama and Santaren Channels. and a ~ed.iterr?nean have been published. C. large area east and north of the Baha- the "small" group) there. Plccmettl ~personal communication), mas. Virtually all ofthe mature bluefm The only occurrence of early stages however, mformed the senior author ofbluefm in the eastern North Atlantic, taken in these southerly parts of the that the relative abundance of larvae in western North Atlantic and adjacent or the South Atlantic of which we have the Gulf of Mexico, as indicated by waters for which we have size data knowledge is the collection of a very Montolio and Juarez (1977), was much few larvae near the Equator and longi- ":ere large .(0~erI85 cm long) indi- less than that which he and his col- Viduals, welghmg over 125 kg. Exami- tude 7°W. Much more information will leagues had found in parts ofthe Medi- nations of gonads suggest that at least be needed to determine the significance terranean. some smaller bluefm spawn near the of this unexpected finding.

95 VI. MIGRATIONS AND STOCK IDENTIFICATION

A. INTRODUCTION B. METHODS AND MATERIALS, c. Methods Used Mainly for Studying Migrations Identification of Atlantic blue- AND DEFINITIONS Most of the methods listed be- fin tuna stocks is regarded as one of low were developed to study migra- the most important prerequisites to 1. Methods and Materials tions, but tagging is equally useful the efficient management of its fish- a. Deductive Methods for identifying stocks: eries. The studies of stock identifica- Deductions in regard to migration and migrations are so closely (1) Visual tracking from aircraft. [Vi- tions and the identity of stocks have related as to be almost inseparable. sual observations from vessels or been based on observations or infor- Some methods, such as the visual or shore come under item a(4).] mation of the following types: electronic tracking of fish, and the (2) Tagging; analysis of the seasons and localities (I) The times of appearances and dis- (3) Tracking with sonar. of catches, relate primarily to migra- appearances of the fish in fishing tions. Others, such as biometric and areas and the observed move- (4) Tracking with sonic tags. biochemical studies, are more directly ments of the fisheries for it. concerned with stock identification. (2) The size or age composition of d. Development of Bluefin Tagging is one of the most positive the catches. Tuna Tagging Tagging is the only positive methods of studying both problems. (3) The sex ratio ofthe catches. In difficult cases, however, it is nec- method of determining that an indi- essary to use all available means to (4) The observed behavior of the fish vidual fish has gone from one place ,-- achieve either objective. This is es- in specific areas and seasons. to another. The desirability of tag- - ging Atlantic bluefin tuna was rec- pecially true of the bluefin tuna, (5) The apparent preferences of the ognized long ago (Sella 1912b), but whose long, rapid and variable mi- fish for environmental conditions, the technical difficulties were such grations make their migratory pat- and their seasonal changes. terns and populations especially dif- that it was not accomplished on a (6) Deductions as to the localities ficult to identify. continuing basis until 1954 (Mather where specially constructed i Until 1954, when sustained tag- 1960, 1963). Sella (1927) tagged 2~ hooks and lures found in bluefin ging of the Atlantic bluefm was initi- bluefin tuna weighing from 4 to 20' tuna caught in traps had origi- ated, scientists were limited to de- kg off Gallipoli (southern Italy) in nated. ductive, or indirect, methods of study- 1912 with bands around the caudal peduncle, but no returns resulted. HIS ing its migrations. Likewise, until the b. Methods Used Mainly for development of biochemical meth- (1927, 1929a) deductions of migra~ Identifying Stocks tions from hooks and lures found in ods at about the same time, they de- Just as many of the above meth- pended mainly on biometric studies tuna caught in traps, however, ods have been used to identify stocks aroused new interest in the problem. to identify its populations. Even with as well as to study migrations, the the aid of these and other advanced Methods of marking were discussed following ones, which have been used extensively at the "Conference of ex- techniques, the migratory patterns of primarily for stock identification, bluefm tuna are not completely un- perts-" (Anonymous 1932b), and have also been applied to the study the tagging of bluefin tuna was derstood and the stocks have not been of migrations: positively identified. strongly recommended. Large and (1) Anatomical comparisons. In this section we will consider small bluefin tuna were tagged off the migrations and stocks (without a (2) Biometric comparisons of mor- Portugal in the years 1931-1935 and priori implication that they are sepa- phological characters. 1960 (Frade and Dentinho 1935, rate) in the Mediterranean-eastern Heldt 1938, Vilela 1960). Some large (3) Comparisons of biochem ical individuals were also tagged off Tu- Atlantic area and in the western At- properties. lantic. Finally, we will consider the nisia and Morocco (Heldt 1943). In implications of trans-equatorial and (4) Comparisons of areas and sea- addition Heldt (1932) distributed transatlantic migrations and present sons of spawning. marked hooks to tuna fishermen at our conclusions in regard to the iden- (5) Comparisons of growth rates. Groix, France, on the Bay of Biscay tity of stocks. in 1927, 1928 and 1929. Many of the hooks and lures retrieved by Sella (1929a) from tuna which had been caught in Mediterranean tuna traps

96 were of the type ordinarily used in Cooperative Game Fish Tagging Pro- for the Facilitation of Tuna Research that bay. English sport fishermen, co- gram of the Woods Hole Oceano- (1972), Mather and Mason (1973, operating with F. S. Russell (1934a), graphic Institution, which has been 1976), Mason (1975), and Mason et left marked hooks in a number of conducted jointly with the National at. (1977). giant bluefm tuna in the North Sea in Marine Fisheries Service since 1974, 1933. Since no returns resulted from developed from these beginnings. all of these efforts, interest in the Subsequently agencies in other At- 2. Definitions matter subsided again. lantic and Mediterranean nations have Direct migration-This term is used The first successful tagging· of marked bluefin tuna and other large to designate the movement of a Atlantic bluefm tuna was achieved pelagic species with interesting and fish which presumably could not by Westman and Neville (I 942), who important results. have been repeating an annual marked 23 small bluefin tuna with migratory pattern when recap- celluloid disc tags off New York Har- e. Summary of Dluefin Tuna tured. It does not imply that the Tagging Programs bor during the 1941 fishing season. fish has travelled on a straight A summary of the more impor- They obtained two returns in the same course from one point to another. tant programs, with the major areas locality and season, after periods of and dates of operation and major lit- Trap fisheries-Special terms of the less than 75 days at large. Interest in erature references for each, follows: trap fisheries have been defined such matters of course ceased with in Section IIB4. the outbreak of World War II. Canada - Fisheries Research Board of Canada (now Environment Cooperating sport fishermen 3. Hypothetical Migration Model Canada). used numbered hooks furnished by Subject to some variations be- Schuck and Mather to mark giant S1. Andrews Biological Laboratory tween successive ages and overlaps bluefin tuna off the Bahamas in 1950 -N orthwestern Atlantic- I 963- between age groups, and some re- and 1951, and off Rhode Island in present, Beckett (1970), Burnett gional differences, we believe that 1952 (Mather 1963). Rivas (1954) et al. (1977). the basic migratory behavior of the also used the numbered hook method France - Institut Scientifique et bluefin, through its life in the Atlan- to mark giant tuna off the Bahamas Technique des Peches Maritimes- tic, may be summarized by age groups in 1952 and applied strap tags to the Bay of Biscay and Portugal-I 968- as follows: opercles of some of these fish, like- present, Aloncle (1973). Very Small Fish (Less Than 2.5 kg, wise utilizing the cooperation of rod and Age 0) - Development from and reel anglers. The only result from Italy - Centro Sperimentale delIa egg to active predator is ex- all these efforts was the return, about Pesca- Tyrrhenian Sea- I 962- tremely rapid. Hatching occurs fifteen years after its recovery, of a present, Arena and Sara (J 967), within two days. The larvae be- numbered hook from a fish recap- Arena and Li Greci (1970). come active swimmers in 15 days, tured from Wedgeport, Nova Scotia. Morocco - Institut des Peches and a length of 30 cm may be The release data for this hook, which Maritimes du Maroc-Atlantic attained within three months. The had been sold by a tackle dealer in coast of Morocco-I 972- I 973, first important movement of the eastern Long Island, New York, had Lamboeuf (1975). newborn fish is one of concen- not been reported, and our efforts to tration. They migrate from ex- retrieve this information were unsuc- Norway - Fiskeridirektoratets tensive spawning areas to lim- cessful. The fish probably had been Havforskningsinstitutt- West ited nursery (feeding) grounds. released, or broken free, off eastern coast of Norway-1957-I962, Growth during their first winter Long Island, but of course this is Hamre (1965). is much slower than it was dur- uncertain. Spain - Instituto de Investigaciones ing the warm season. Interest in tuna tagging was re- Pesqueras - Cadiz area, Spain- vived when the California Depart- 1960-1967, Rodriguez-Roda Small Fish (2.5-32.0 kg, Ages 1-4, ment ofFish and Game developed (1963, I964c, 1969a). Immature) - These fish make the dorsal loop tag and used it suc- annually repeated two-phase mi- United States of America - Woods cessfully on small Pacific tunas (Wil- grations between limited warm Hole Oceanographic Institution son 1953). Mather, with the coopera- season coastal nursery areas and and National Marine Fisheries tion of a few interested sport fisher- little known, but presumably Service - Northwestern Atlan- men, proved the feasibility of mark- more extensive, cold season win- tic and adjacent waters-1954- ing small Atlantic bluefin with the tering areas. The warm season present and I974-present, respec- dorsal loop tag in Massachusetts wa- occurrence is typically in the sur- tively, Mather (1960, 1962, 1969, ters during the 1954 fishing season. face layers, with heavy feeding 1974a), Mather et al. (1967, He concurrently developed the dart and rapid linear growth, but no I974b), Mason et al. (1977). tag, with which even very large fish decrease in the length-weight ra- could be marked rapidly once they The results of tuna tagging have tio. The winter sojourn, on the were brought alongside the boat been summarized and briefly de- other hand, occurs at deeper lev- (Mather 1960, 1963). The successful scribed by the FAO Panel of Experts els, and growth virtually ceases.

97 Consequently, feeding and gen- growth are presumed to be re- Sara (1964, his Figure 5) showed eral activity are presumed to be duced during their wintering pe- the approximate locations of the greatly reduced. The migratory riod in deep waters. Movements significant traps still in use in the behavior of mature individuals within some of these seasonal early 1960s, indicating, for each, the in this group often resembles that habitats have been observed, as fishing period and the direction from of the medium fish. well as the migrations between which the fish entered the trap. The data for those in the Ibero-Moroccan Medium Fish (32-122 kg, Ages 5-8, them. Bay and the extreme western Medi- Mature) - These fish make an- We shall discuss the migratory terranean (Figure 45) strongly sug- nually repeated three-phase mi- patterns of the different size groups gested eastward movements from the grations between warm season of bluefin tuna in terms of this sim- Atlantic into the Mediterranean ("ar- feeding areas, deep water win- plified model. rival") in May and June, and move- tering areas, and late spring ments in the opposite direction ("re- spawning areas. The warm sea- C. STUDIES OF MIGRATIONS turn") in July and August. The arrays son distribution is more exten- AND STOCK IDENTITY of "arrival" traps on the sides of the sive than that of the small fish, Bay terminated at Tarifa (north coast) and not as limited to coastal wa- and Cape Spartel (east coast), show- ters. This occurrence is again fre- 1. Mediterranean and Eastern ing that the "arrival" run extended at quently in the surface layers, but Atlantic least up to the very threshold of the not as predominantly so as that a. Introduction Strait of Gibraltar. of the small fish. Feeding is The earliest speculations and hy- Data for the "return" traps sug- heavy. Seasonal linear growth has potheses aboutthe migrations of blue- gested that some west-bound tuna fol- not been determined, but is pre- fin tuna, and in fact nearly all of lowed both coasts of the Mediterra- sumab]y rapid. The length-weight those before ] 920, were concerned nean as they approached the Strait. ratio decreases considerably dur- with the Mediterranean and eastern ]n the Ibero-Moroccan Bay, however, ing this period. The cold season North Atlantic areas. In fact, the study they occurred in much greater distribution is much wider than ofthese migrations undoubtedly de- strength along its northern (Iberian) that of the small fish, extending veloped from observations made dur- coast, in contrast to the complete ab- far into oceanic waters. These fish ing fishing operations in the Medi- sence of a "return" trap fishery along then remain in the subsurface lay- terranean and its approaches during its eastern (Moroccan) coast. ers and it is assumed, but has not the pre-Christian era. Traps similar The other important group of been demonstrated, that their to those still in use apparently ex- traps shown by Sara (I964) was in feeding, activity and growth are isted then, but movable nets, whose the central Mediterranean. Most of reduced. In late ,spring and early successful operation required the these fished the "arrival" run only. summer, many of these fish con- assistance of watchers (thynnoscopi) The indications from the dates and centrate in spawning areas which situated at coastal vantage points, directions in which the fish entered are little known. After spawning were probably more numerous the traps were as follows. they return to the warm water (Parona ]919, Thomazi 1947). Both Off Tunisia, the "arrival" tuna season feeding areas. methods depended on the movements apparently travelled eastward from Large or Giant Fish (Over 122 kg, of schools of fish along the coasts, Bizerte to the Cape Bon peninsula, Age 9 or Older, Mature)- The which occurred mainly during the which they rounded, then moved fish make three-phase migrations runs of maturing (now known as "ar- southward to Ras Kapudia. "Arrival" basically similar to those of the rival") tuna in May and June, and bluefin also evidently moved east- medium size group, but their dis- post-spawning (now known as "re- ward along the Libyan coast, from tribution and migrations are much turn") fish in July and August. There- Zuara near the Tunisian border to more extensive. Their spawning fore, before recapitulating the devel- Cape Misurata (longitude] 5°E). and migratory periods, as well as opment of hypotheses on the migra- The situation around Sardinia, the areas concerned, while dif- tions and populations of tuna in this Sicily, and Italy differs because of fering somewhat from those of region, we will summarize some of the disjointed configuration of the the medium group, overlap or co- their local movements which have coasts. The "arrival" fish tended to incide with them to a consider- been indicated over the ages by the move in southerly directions along able degree. The season a] linear operations of the traps which have the western shores of Sardinia, and growth of these fish is not known, harvested these periodic passages. also along the Calabrian coast in the but their length-weight ratio de- Basic data which will be considered Gulf of Sant' Eufemia. With local creases greatly during the feed- include the location of the traps, the exceptions at its two extremities, "ar- ing season, and increases corre- direction from which fish must ap- rival" fish travelled westward along spondingly during spawning and proach them, and the periods when the north coast of Sicily, following their post-spawning migrations. they catch tuna. The relative impor- the western sides of bays and the As with the smaller groups, their tance of their catches will be dis- eastern sides of promontories along feeding, general activity and cussed in special cases. the way. This westward movement is

98 directly opposite to the usual "ar- ter. Scordia (1938) and others (Ninni Numerous biometric compari- rival" pattern. 1922, Genovese 1957) thought that sons of morphometric and meristic The "return" situation is much there were two or more stocks of characters of bluefin tuna from vari- simpler. Tuna apparently swam bluefin within the Mediterranean, ous areas were carried out to identify southward along the southern half of each native to its particular basin. populations or races (Frade 1931, the east coast of Sicily, and west- Some authors even questioned Arico and Genovese 1953, Nede lec ward along the western half of its whether bluefin tuna actually oc- 1954, Genovese 1957, 1958). More southern coast. curred in the Atlantic (except in the recently, some genetic and biochemi- The above discussion is obvi- Ibero Moroccan Bay) in significant cal research has been undertaken for ously simplified, and is only intended numbers, or whether the bluefin re- the same purpose (Keyvanfar 1962, to show trends in the movements of ported from the Atlantic were of the Lee 1965, 1968). the tunas. There have been many same species as those in the Mediter- Despite all of these efforts, un- varying opinions on how the tuna ranean. certainties about the migration pat- approach the coasts and enter the traps These theories were predominant terns and the identity of the stocks in (Scaccini and Pacagnella 1965). We in the late 1800s and early 1900s, the eastern Atlantic and the Mediter- do not mean to imply that the entire until Sella (1926a, 1926b, 1927, ranean still exist. mass of fish in a given area follows 1929a, 1929b, 1930, 1932a, 1932b) the route described, but only that hypothesized several migrations from b. Migrations Between the Mediterranean and the many fish in the respective areas tend various Atlantic areas and from the Eastern Atlantic to travel in the stated directions. Sea of Marmara into the Mediterra- Unit stock or two stocks? - The Most of the early theories on the nean, as well as between the differ- question of whether the bluefin tuna migrations were based mainly on in- ent basins of that sea. He deduced constitute a single stock which mi- formation ofthe type which has been these migrations by determining the grates from the Atlantic into the summarized above. It should be localities where hooks and lures Mediterranean to spawn and then out noted, however, that the European found in bluefin, which had broken again, or comprise two stocks - one fisheries have a very ancient history, lines or leaders and subsequently been Atlantic and one Mediterranean - whereas most of those in Africa origi- caught in traps, were in general use. has been debated for decades. This nated in modern times. In that period, tuna fishermen used discussion led to such terms as the The theories on migrations of hooks and lures which were hand- "migratory" or "sedentary" tuna, (re- bluefin, developed largely from stud- made locally. Distinctive designs and ferring to the supposed habits of the ies of the trap catches, and later from methods of attachment to lines or fish) and the "unitists" or "dualists" consideration of environmental fac- leaders made hooks and lures from (referring to the theories on the num- tors as well, varied from Aristotle's different localities easily recogniz- ber of stocks). (circa 325 B.C.) view that the bluefin able. Thus it might be assumed that a Ancient trap fisheries in the was an Atlantic species which occu- fish found carrying a hook or lure Mediterranean Sea and its approaches pied the Mediterranean only on its typical of a given area had come from were based on the spawning runs of way to and from its supposed spawn- that area. In some cases, this prob- the larger bluefin: an eastward "ar- ing grounds in the Black Sea, to the ability was greatly increased by many rival" run, mostly of fat fish with concepts of Pavesi (1889), Sanzo findings, indicating similar migra- ripening gonads, in May and June (1910a), Roule (1914a), F. de Buen tions. This somewhat uncertain and a westward "return" run, mostly (1925), and Scordia (1938) that the method was followed by the more of lean spent fish, in July and Au- Mediterranean and Atlantic bluefin positive ones of sonar tracking gust. These runs were the basis of the constituted entirely separate popula- (Lozano Cabo 1959a, 1959b) and tag- Aristotelian theory, that the bluefin tions. Pavesi (1889) thought that the ging (Rodrfguez-Roda 1964c, 1969a; was essentially an Atlantic species, Mediterranean bluefin was an abys- Hamre 1965, Arena and Li Greci but passed through the Mediterranean sal animal, rising from the depths of 1970, Aloncle 1972, Lambouef in May and June to spawn in the that sea and moving to nearby sur- 1975). Studies of the effects of Black Sea, and returned to the Atlan- face waters only to spawn. Bounhiol environmental conditions on the oc- tic in July and August. This theory (1911) shared in the concept of a currences and behavior of tunas, par- has been accepted, wholly or in part, strictly Mediterranean bluefin stock ticularly during the spawning sea- by nearly all of the trap fishermen to but believed that its apparent migra- son, and analyses of the time, loca- this day, and also by many scientists. tions were actually the result of a tion, quantity and size composition Objectors (Pavesi 1887, 1889; tendency to swim against the wind- of catches, continued to provide de- de Braganya 1899, Sanzo 1910a, driven currents. Roule (1914a) felt ductive indications in regard to mi- Roule 1914a, 1914b, 1917, 1924; F. that the bluefin was a pelagic crea- grations concurrently (J. Le Gall de Buen 1925, 1931; O. de Buen ture which migrated only within the 1929,J.Y. LeGa1l1974, Hamre 1958, 1924, Scordia 1938) noted that blue- basin of the Mediterranean in which 1962, 1965; Lozano Cabo 1958, fin spawned in the Mediterranean and it lived. He believed that its spawn- Rodrfguez-Roda 1963, 1964a, 1969b, that individuals of all sizes were ing migrations were controlled by the 1970a, 1970b; Aloncle 1964, Arena present in it throughout the year. They temperature and salinity of the wa- 1964, Sara 1964, 1973; Tiews 1964). also maintained that the lag which

99 would have occurred between catches that there were relatively few large Barbate and Cadiz, Spain, and in "arrival" traps located in westerly bluefin in the Mediterranean except Larache, Morocco, in June and July areas and those in easterly areas, if during the spawning migrations and 1957, he obtained data which he con- all were fishing a single group offish that the arrival fishery actually did sidered sufficient to provide interest- moving eastward, did not exist. Roule begin later in the season in propor- ing conclusions on the biology ofthe and F. de Buen used the relatively tion to how far east the traps were species. poor bluefin catches in the Sea of located. Lozano Cabo (1958) had1ius- Alboran (just east of Gibraltar) as After this long period of indirect pected that bluefin, at least during another argument against a large scale studies, Sella's (1927, 1929a) find- their spawning migration, might be spawning migration of bluefin from ing of25 Atlantic hooks and lures in negatively rheotactic (tending to the Atlantic into and out ofthe Medi- tuna caught in Mediterranean traps swim with the currents). The detec- terranean. Both of these scientists revived the "migratory" or "unit tion of schools confirmed this. The cited the sensitivity of the bluefin stock" theory. The items recovered greatest number of "arrival" schools tuna to environmental conditions as included 13 from Tarifa, seven cer- were found in the middle of the Strait, evidence that they could not pass tainly and two probably from the Bay where the current always favored through the relatively cold (R. de of Biscay, two from the Azores, and their eastward passage. Many schools Buen 1927) waters of the Strait of one from south ofIreland. These star- were also found on the northern side, Gibraltar, especially during the tling revelations did not pass where the current was usually favor- spawning season. Roule (19 I 7) pro- unchallenged in this period when the able, but they were very rare on the posed the "ha10thermic" theory, "sedentary tuna" theory was deeply Moroccan side, where the currents maintaining that the bluefin were rooted in the minds of nearly all the tended to vary with the tides. The "stenotherms" and "stenohalines", scientists concerned with the prob- depth at which the schools traveled and sought the warmest and most lem. F. de Buen (193 I) and Scordia was difficult to determine, but ap- saline waters during the spawning (1934) questioned Sella's deductions, peared to be somewhat less than 60 season. F. de Buen (1925) opted for on the grounds that fishermen from m. the "thermic" theory, considering the localities where the hooks and The migration route of arrival at water temperature to be the domi- lures were made might actually have the Strait when departing from the nant factor controlling the tunas' used them while travelling in other Atlantic followed the Spanish coast. movements. Both agreed, as did most areas. Although they admitted that a Some schools were located between students ofthe subject in the Mediter- few such migrations might occur, Cape Spartel and Cape Malabata (on ranean and adjacent Atlantic waters, they maintained that they probably the southwestern side of the Strait), that the sensitivity of the bluefin tuna were not related to the spawning but none were detected south of Cape to the environment increased during cycle, and were relatively insignifi- Spartel during numerous cruises be- the period of maturation. cant numerically. Sella (I 929a) had tween Tangier and Larache. Perhaps Scordia (1938) also believed in already pointed out, in support of his the tuna which came from the Afri- the "sedentary" tuna theory and felt hypothesis, that the findings of the can coast partially crossed the Strait that few, if any, bluefin tuna entered hooks varied according to the inten- from off Cape Spartel toward Tarifa, the Mediterranean from the Atlantic. sity of fishing in the area of their and joined those coming from the Like Roule (I914a, 1914b, 1917) and origin. When the fishery off Tarifa Spanish coast, or followed routes F. de Buen (1925), she stressed the was important, numerous hooks of similar to theirs through the Strait. increased sensitivity of the maturing the very distinctive type used there The schools which had tended to con- tuna to its environment. were recovered in the Mediterranean. centrate in the center of the Strait Sella (1929a) showed, however, After the fishery off Tarifa had de- while traversing it appeared to dis- that bluefin tuna could withstand ex- clined drastically, and the one in the perse as they entered the Mediterra- treme changes in temperature and Bay of Biscay had increased greatly, nean at the Ceuta-Algeciras line. salinity during their feeding period. hooks of the former area were no In general, the migrating tunas He maintained that even during the longer found, but hooks of the Biscay appeared to prefer temperatures of spawning period they sought specific type appeared in numbers. Sella also 18°C to 21DC, but deviations from conditions which varied with size of noted that, considering the enormous the preferred temperature were more fish, rather than maxima as proposed odds against recovering a lost hook frequent in the Strait than at the traps. by Roule (19 I7). He further argued in a tuna, the numbers of findings Lozano Cabo attributed this to the that the "thermic" or "halothermic" indicating these migrations were too overcoming of temperature sensitiv- barrier of F. de Buen (1925) and large to be attributable to casual fish- ity by the reproductive urge. Nearly Rou1e (1917) did not constitute proof ing by transients. all previous scientists (Roule 19I4a, that bluefm could not pass through Detailed information on the Sella 1929a, Scordia 1938) had main- the Strait of Gibraltar, but would be movements of bluefin tuna in the tained that the sensitivity of the blue- an explanation of such a situation, if Strait of Gibraltar obtained by echo fin to temperature and salinity was its existence were substantiated. sounder was reported by Lozano greatly increased during the spawn- Sella noted, as Sara (I 964, 1973) Cabo(1959a, 1959b). In 2,000 miles ing period in contrast to the "erratic" and Scaccini et al. (1975) did later, of cruising in the Strait, and as far as (feeding) period. In any case, Lozano

100 Table 27. Release and recapture data for bluefm tuna tagged in the Gulf of Cadiz, Spain and off Sicily with size at recapture and months* at liberty.

Return Release Release Release Recapture Recapture Recapture Length Weight Months Number Area Location Date Area Location Date (em) (kg) at Liberty

1 Sancti-Petri 36° 22' N 06° 16' W V-1960 Portugal 37° 00' N 07° 36' W V-1960 170 110 0.0 2 Barbate 36° 09' N 05° 56' W V-1960 Spain 36° 09' N 05° 20' W VII-1960 173 90 2.1 3 Barbate 36° 09' N 05° 56' W VII-1960 Spain 37° 07' N 07° 07' W VIIl-1960 174 70 0.4 4 Barbate 36° 09' N 05° 56' W V-1960 France 43° 30' N 03° 56' E VIIl-1960 136 41 2.8 5 Barbate 36° 09' N 05° 56' W VII-1960 Portugal 36° 50' N 07° 54' W V-1961 190 120 10.0 6 Barbate 36° 09' N 05° 56' W VII-1960 Morocco 35° 12' N 06° 10' W VI-1961 100 10.4 7 Barbate 36° 09' N 05° 56' W VI-1961 Spain 35° 52' N 05° 15' W VII-1961 195 83 0.6 8 Barbate 36° 09' N 05° 56' W VII-1961 Portugal 37° 00' N 07° 36' W VII-1961 90 0.1 9 Barbate 36° 09' N 05° 56' W VII-1961 Spain 37° 07' N 07° 07' W VII-1961 0.2 0 10 Barbate 36° 09' N 05° 56' W V-1962 Portugal 37° 00' N 07° 36' W V-1962 133 44 0.1 11 Barbate 36° 09' N 05° 56' W VII-1960 Morocco 35° 12' N 06° 10' W V-1962 199 136 22.1 12 Barbate 36° 09' N 05° 56' W VII-1960 Morocco 35° 12' N 06° 10' W VI-1962 185 162 22.5 13 Barbate 36° 09' S 05° 56' W VIIl-1962 Portugal 37° 00' N 07° 36' W VIIl-1962 70 0.4 14 Barbate 36° 09' N 05° 56' W VIIl-1962 Morocco 31° 30' N 09° 50' W XII-1962 175 3.2 15 Barbate 36° 09' N 05° 56' W VII-1965 Portugal 37° 00' N 07° 36' W VII-1965 . 220 270 0.2 16 Barbate 36° 09' N 05° 56' W VIIl-1967 Spain 37° 30' NOlo 00' W VIIl-1967 165 120 0.8 17** Barbate 36° 09' N 05° 56' W Libya 32° 58' N 13° 12' E V-1965 18** Barbate 36° 09' N 05° 56' W Libya 32° 58' N 13° 12' E V-1965 19 Punta Raisi 38° 08' N 13° 22' E V-1968 Spain 40° 00' N 00° 00' X-1969 45 16.6

*0.0 indicates less than 1.5 days. ** These tags were not returned. The recoveries were reported without the tag numbers. ever, was during the "return" run, when they are thought to be travelling westward. The recaptures were all in July or August, during the "return" run. Times at large varied from 19 to 23 days, and the weights of the fish were 41,83,90 and 120 kg (medium size range). These returns demonstrate conclusively that some bluefin enter the Mediterranean from the Atlantic. They also suggest that some 40" of these fish return to the Atlantic since the traps at La Linea and Ceuta: at the extreme western end of the Mediterranean, are designed to fish LEGEND the "return" (westward) run only. o RELEASE LOCALITY • A[CAPTuItf LOCAUTY The recovery of two Spanish tags - LESS TN". iO MONTHS AT LlIERTY ---IiIOAE THANfOIIIONTMSATLIKRTY from bluefin tuna caught in a trap o ~:u.:,~=~::NT INDIVIDuAl.1~tf'gl.' near Tripoli, Libya, was reported, but the tags have not been returned, nor 30° .' NOTE; {IN£$AM USED aNLr TO JOIN ReLEASES have their numbers been ascertained AND RETIPINS WHICH "1IC 1/101I£ TNAN ~ ItM ••• t:I 0 UARr AND ARE DJAfiRAMIiAr/C AND AI'i£ Nor (Rodriguez-Roda 1969a). INTENDED TO II£PRES£Nr MI611"TION /H}{JT£S. The Atlantic recaptures (15) were much more numerous than those o in the Mediterranean (4), but the probability of recapture of a tagged bluefin seems to have been much greater Figure 71. Geographic distribution of bluefin release and recapture in the Ibero-Moroccan Bay than in data shown in Table 27. the western Mediterranean. The fisheries in the former area took many more bluefin in the period 1960-1967 Cabo has apparently provided first- the Atlantic into the Mediterranean. than those in the latter. Much more hand evidence against the existence He marked 312 bluefin tuna, ranging tagging is needed to evaluate the mi- of the thermal or halothermic barrier from 60 to 220 em in length, from grations between the Atlantic and the to maturing bluefin at the Strait pos- catches in traps near Cadiz, Spain, in Mediterranean quantitatively. tulated by Roule (1914a), F. de Buen 1960-1968. Four of these fish were Much meristic and morphomet- (193 1) and others. recaptured in the Mediterranean and ric data on bluefin tuna from various The sizes of schools were also 15 in Atlantic waters off southern areas of the eastern Atlantic and the difficult to determine. Lozano Cabo Spain and Portugal and western Mo- Mediterranean are available, and sev- estimated that one of the largest rocco (Table 27, Figure 71). eral comparisons of the data for fish schools, observed on June 21, 1957, The Mediterranean returns are from different localities have been between Algeciras and Tarifa, Spain, of special interest, in view of the 3 made (Tiews 1963). Sella (1929a, occupied about 7,200,000 m • If the long debate as to whether or not im- 1930) noted that he had made several fish were 20 m apart in all dimen- portant numbers of bluefin tuna mi- observations on tuna from Spain, sions, their number would have been grated through the Strait of Gibraltar. Calabria (Italy) and Tripoli (Libya), 1,922. If the spacing were reduced to Two of the fish were recaptured at without finding differences sufficient 10 m, the number would be 11,163. La Linea and Ceuta, Spanish ports to justify any racial demarcation. He Lozano Cabo estimated the av- on the north and south sides of the did not, however, publish these data. erage speed of the schools at less Mediterranean outlet of the Strait Frade (1931) concluded that there than 7 knots (13 km/hr). He pointed respectively, and about 40 nauticai were significant differences between out that, although the schools ob- miles (64 km) from the release point. the tuna which he had examined on served in the Strait were numerous The other two, recaptured off the Portuguese coast and those which and large, it should be recalled that Cartagena, Spain, and Palavas, Heldt (1927b ) had measured in Tu- 1957 was a very good tuna year. France, had penetrated much more nisia. Nedelec (1954) compared mor- Some uncertainties may exist in deeply into the Mediterranean, 270 phological data from bluefin tuna cap- regard to the actual origin of Sella's and 675 nautical miles (431 and 1,080 tured in the North Sea, off southern (1927, 1929a) hooks and the identity km) respectively, from the release Portugal and off Tunisia. He con- of Lozano Cabo's (1959b) sonar tar- point. Three of the releases were in cluded that the North Sea samples gets, but Rodrfguez-Roda (1963, May and June, during the "arrival" were close to those from Portugal, 1964c, 1969a) provided indisputable run when the fish are supposed to be but that both differed considerably proof ofbluefm tuna migrations from travelling eastward. The fourth, how-

102 from those from Tunisia in many presence in the Gulf of Lion or indeed, even now (Sara ]973). characters. Arico and Genovese (Mediterranean) of certain individu- Both authors indica'ted, however, that (1953) and Genovese (]957, ]958) als which belong to a race or to a these smaller reproducers spawned compared morphological data for population different from that ob- later than the larger ones. spawning and feeding tunas taken off served in the Bay of Biscay. Sara (1964, ]973) has proposed northeastern Sicily with similar data These biometric and biochemi- a hypothesis which reconciles many for b]uefin taken off Tunisia and cal studies provided interesting of the seemingly contradictory facts southern Portugal and in the North information, but, in our opinion, they in regard to the relations~ips between Sea. They concluded that the two were inconclusive in determining eastern Atlantic and Mediterranean Sicilian samples were from a single whether the bluefin in the Mediterra- bluefin tuna. He believed that a num- Tyrrhenian stock which was distinct nean and eastern Atlantic constituted ber, determined by the environmen- from the fish from the other three a single or separate stocks, or to what tal conditions existing then and in areas and also from smaller samples degree mixing occurred. the preceding few weeks, of large taken off the Mediterranean coast of ]n summarizing his extensive (over 100 kg) bluefin tuna gathered France, and off Algeria. studies of the fisheries and migra- in the Ibero-Moroccan Bay in late Tiews (] 963) summarized, com- tions and other aspects of the biology April and early May, "hesitating" pared and discussed these data and of the species, Sella (] 929a, 1930) (Lenier 1959) there. Then a portion studies. He found that only the dif- proposed the following four phase of these, the number again depen- ferences in head length, pectoral fin migratory cycle for bluefin tuna: dent on environmental conditions, length and number of finlets support a. Gathering of bluefin in May-June entered the Mediterranean to spawn, the case for the existence of separate in re]atively limited spawning ar- and subsequently returned to the At- stocks on the European side of the eas in the southern part of its lantic. Atlantic. In view of the long and rapid range (Mediterranean, Ibero-Mo- Lozano Cabo (] 958) and Aloncle migrations of blue fin demonstrated roccan Bay) (] 964) showed that the average sizes by tagging experiments, however, he of the bluefin taken in the Atlantic b. Post-spawning dispersion, mainly did not believe that the above differ- traps, both in Morocco and along the northward, with the maximum ences would stand up under critical south coasts of Portugal and Spain, extension of their habitat occur- inspection. He predicted that further varied inversely with the distance of ring in the warmest part of the studies would prove the existence of the trap from the Strait of Gibraltar. summer and autumn. a single bluefm population in the east- The largest bluefin (by average ern North Atlantic. c. New reduction in habitat with the weight) have been taken by the traps Genetic and biochemical char- coming of winter. This distribu- of Tarifa and Cape Spartel, at the acteristics of bluefin tuna from the tion was not well known, because very entrance to the Mediterranean. eastern Atlantic and the Mediterra- the fish were farther below the Actually, more small fish were taken nean have also been investigated and surface, but was presumed to be in the more westerly and southerly compared. Keyvanfar (] 962) studied considerably reduced, with ma- traps. This was a good indication that the serology and immunology of jor withdrawal from the more the larger bluefin were more apt to bluefin tuna from the Atlantic and northerly area. enter the Mediterranean than the Mediterranean coasts of France. ]n- d. In March-April, immediately pre- smaller ones, just as Sara (1973) hy- dividual differences in immunology ceding the reproductive period, pothesized. between Mediterranean samples were the tuna made another northward Sara (] 973) stated, moreover, found but the samples were too few migration which was much more that daily catch records collected con- in number, particularly those from limited than that in summer-au- tinuously during the fishing seasons the Atlantic, to furnish any inter- tumn. They appeared en masse for several years showed that the first pretation on migatory tendencies. Lee off the north coasts of the Medj- catches of the Cape Spartel trap, at (1965) provided further information terranean and the Spanish coast . the entrance ofthe Strait, consistently on the serology and immunology of of the Bay of Biscay. preceded the first of the traps off the bluefin from the French Mediter- western Sicily by from seven to nine The subsequent development of ranean coast and (] 968) comparisons days. This 900 nautical mile (1,675 fisheries covering nearly all suitable of the immunology of bluefin tuna km) itinerary would require average waters of the Atlantic, and modem from the eastern Atlantic (30 speci- speeds between 4.2 and 5.4 knots research, including tagging and track- mens) and the Mediterranean (72 (7.7-] 0.0 km/hr). This range does not ing with sonar, have shown how ac- specimens). Lee found individual dif- differ greatly from the migrating curate Sella's concept was. The only ferences even within the samples speeds 'observed by Lozano Cabo dubious point is his fourth phase, the from the Atlantic and those from the (I959b), less than seven knots (13.0 pre-spawning northward migration. Mediterranean. She also found that km/hr), and by Rivas (1955, ]976), This probably consists of immature the percentage of individuals with no four knots (7.4 km/hr), or from the fish and the younger mature ones, antigens and those with one or sev- average speed of a giant bluefm which concerning whose spawning habits era] differed in the two lots. She con- migrated from the Bahamas to Nor- little was known then (Sella 1929a), cluded that one might consider the way in 50 days (Mather ]969), 3.5

103 knots (6.5 kmlhr). These facts refute turn" trap fisheries along its African first year of life, when they weigh the argument that no lag between the coast. about I kg. This ties in with the dis- catches in the respective localities Sara (1973) believed that the appearance of age 0 bluefin weigh- existed, or that it was so short that smaller bluefin (less than 100-150 ing about I kg from the Mediterra- impossible speeds would have been kg) did not participate in this Atlan- nean coast of Spain in October, and required for a tuna to have accom- tic-Mediterranean migratory pattern. the regu lar appearance of age 0 blue- plished the implied migration (Pavesi He felt, as did Sella (1929a), that the fin weighing about 1.5 kg off the 1887, 1889, Roule 1925) This infor- immature individuals were relatively Atlantic Moroccan coast in the sec- mation, combined with Sella's sedentary. He concluded that the in- ond half of November (Section (1929a) findings of Atlantic hooks dividuals in this size range made ryCS). The massive catches of age 0 and lures in tuna caught in the Medi- longer migrations after reaching ma- bluefin in the fall by the "return" terranean and the tag returns show- turity but that those in the Mediterra- traps and purse seiners at the western ing similar migrations by Rodriguez- nean spawned there and those in the end of the Mediterranean (Rodriguez- Roda (1969a), strongly supports the Atlantic reproduced in that ocean. At Roda 1964b, 1969d; Crespo and Rey old concept that numerous large blue- some period in their development as 1976) also suggest such a migration. fin migrate from the Atlantic into the their weight approaches 150 kg, In 1963, captures around Ceuta in- Mediterranean in May and June. The groups of these fish tend to join the creased sharply in mid-September departure of large bluefin from the groups of larger ones in their Atlan- and remained high until late Octo- Mediterranean in the "return" period, tic-Mediterranean migrations. Sara ber, when they declined. July and August, has been indicated (1973) speculated that this change in by rather small catches in the "re- life style is related to some change in c. Migrations and Stocks Within the Mediterranean turn" traps near the eastern end of the the physiology of the animal, most Much has been written about the Strait (see Section IVC6a). The mod- probably the attainment of the full migrations and stocks of blue fin tuna est size of these catches in compari- development of the swim bladder. in the Mediterranean Sea, but the tag- son with those of the Ibero-Moroc- The sizes of the four fish tagged ging results required to reach defini- can Bay traps may be explained by by Rodriguez-Roda (1969a) near tive conclusions are still lacking. De- Sara's (1973) hypothesis in regard to Cadiz and recaptured in the western ductive studies have lead to widely the depths at which the bluefin travel Mediterranean do not fuBy support diverging opinions, but a reasonable in the respective migratory periods. Sara's view in regard to the sizes of working hypothesis has emerged. He maintained that the "arrival" fish fish which usually follow this route. Since many of the pertinent stud- swam in the surface layers, follow- One of them weighed 120 kg, but the ies have already been discussed in ing the inflowing Atlantic current. weights of the other three ranged from parts a and b ofthis section, they will This is in accord with the fmdings of 41 to 90 kg. Only one of these smaller be recapitulated briefly here, stress- Lozano Cabo (1959b) during his so- fish, however, could have accom- ing the aspects which are relevant to nar survey of the Strait. Sara (1973) plished this migration during the "ar- migrations within the Mediterranean. assumed that, on the other hand, the rival" period which Sara (1973) was According to Aristotle's (circa 325 "return" fish swam at deeper levels, discussing. The results indicate that B.C.) theory, the bluefin was essen- following the outflowing Mediter- casual migrations through the Strait tially an Atlantic fish, but spawned ranean current. He cited a new fish- by bluefin of various sizes may oc- in the Black Sea. Therefore it made ing technique used in the Sicilian cur at any time, but that the mass the circuit of the Mediterranean by Channel as evidence of this (see Sec- periodic movements are carried out passing through it once, en route to tion VIe). Sara believed that this ten- mainly by large individuals. the spawning ground, and again to dency to follow the deep current per- One fact not explained by Sara's return to the ocean. sisted until the gonads had shrunk (1973) theory is the continued Little new information was and the feeding urge became pre- productivity of the fisheries for small added until Cetti (1777) made two dominant. This might occur more bluefin off the Atlantic coast ofMo- very important discoveries. One was readily after the fish had emerged rocco and in the Bay of Biscay (Sec- that bluefin spawned near Sardinia. from the Strait into the Atlantic, tion IYC5). Since there is no hard He surmised correctly, moreover, that where the velocity of the Mediterra- evidence of extensive spawning of more of them spawned in the central nean current diminishes rapidly. The bluefin tuna in the Eastern Atlantic Mediterranean than in the Black Sea. Mediterranean "return" trap at La (Section YD2), important recruitment His other major finding was that me- Linea, on the European side of the to these fisheries from the Mediterra- dium sized bluefin occurred in the Strait, usually caught more large blue- nean seems logical. F. de Buen (1925) Gulf of Sardinia throughout the year. fin than those on the African side. hypothesized a migration of small He named these fish "golfitani", a This is in accord with the tendency bluefin from the Mediterranean to of the "return" tuna to follow the the Atlantic in the autumn of their term which is still in common use. He adhered to Aristotle's basic con- European coast of the rbero-Moroc- second year of life when they can Bay closely, as evidenced by the weighed 4-5 kg. We believe that it is cept, however, and described several distinct routes by which he believed formerly large "return" catches taken more probable that this migration oc- that the larger bluefin reached the there, in contrast to the lack of "re- curs mainly in the autumn of their

104 central Mediterranean. This last find- Ninni believed that the major gard to water temperature, but ing was criticized (Pavesi 1887), but eastward migration of bluefin tuna showed no correlation in regard to recent evidence (Sara 1973) indicates must have departed from the winter- salinity. that it was surprisingly accurate. ing area between Sardinia and Tuni- Sella (1927) disputed Roule's Pavesi (1887, 1889), who was sia, passing along the northeastern (1917, 1924, 1926) hypothesis that the first to seriously challenge the coast of Tunis then along or offshore the tuna which occurred off the south- migratory theory, believed that the from the Tripolitanian coast toward ern coast of France during the re- Mediterranean (and eastern Atlantic) Bengasi. There Ninni's personal ob- mainder of the year spawned in May bluefm spent most of the year in abys- servations ended, but he felt that the and June near the traps off Sardinia, sal waters near their spawning bluefin avoided the Nile outflow and Sicily and Tunisia. He showed that grounds. His theory restricted their turned toward Crete. Ninni thought the tuna caught off the southern coast migrations to a vertical ascent to su- that there was a wintering area around of France averaged only about 20 kg, perficial water and a short horizontal Crete, and possibly another between whereas those caught in the traps av- migration to a nearby spawning Crete and Alexandria, Egypt. eraged from 70 kg to 130 kg. The ground in spring, and short horizon- Ninni hypothesized that when the differences between Roule's and tal return and a vertical descent into fish left the Cretan wintering area Sella's opinions in regard to the sen- the abyss after spawning. they split into two groups. The smaller sitivity of the bluefin to the tem- Sanzo (1910a) agreed with group went up the western Aegean, perature and salinity of the water, Pavesi (1887) in regard to the com- passing between Euboea and the and the effects of these factors on its plete separation of the Atlantic and mainland of Greece and entering the distribution and migrations, have Mediterranean bluefin stocks. He had Gulf of Volos. The larger group fol- been discussed in Section VE2. doubts, however, in regard to Pavesi's lowed the Asiatic coast to the Scordia (1938) maintained that hypothetical bathymetric migrations. Dardanelles and into the Sea of the bluefin tuna which she studied He recommended investigating the Marmara and the Bosphorus, always off eastern Sicily and the west coast darkness or lightness of the colora- leaving the islands on their left. They of Calabria (south~rn Italy) were ofa tion and other characteristics of the passed through the Bosphorus and distinct and separate stock which she tuna when they first arrived at the "lost themselves" in the Black Sea. called the Tyrrheno-Ionian stock. She traps to determine whether they had The passage into the Black Sea be- observed that these tuna remained come from the abyssal depths or from gan March 15 and lasted into Au- mainly in the deep waters of the lower the surface layers. He believed that gust, after which the "return" began, (southern) Tyrrhenian in autumn and spawning was independent of the but not all of the bluefin went back winter, sometimes rising to the sur- coastal movements of the tuna, and into the Aegean. A large proportion face near Messina in the fall to feed. that other causes of their comings of them wintered in the Sea of They surfaced in the spring with the and goings in the Mediterranean Marmara. Ninni's hypotheses do not warm ing ofthe waters to 18°C. When should be sought. lead to an annually repeated migra- increased warming reduced the den- Bounhiol (1911a, 1911b) also tory cycle; in successive years the sity in situ, from between 1.02700 believed thatthe Mediterranean blue- same fish might winter once between and 1.02800 to about 1.02500, the fin tuna stock was separate from that Sardinia and Tunisia, once near Crete, tuna moved from the Tyrrhenian of the Atlantic. He introduced a new and once in the Sea of Marmara. Such through the Strait of Messina into the concept, however, that the bluefin in shifts of habitat (or migratory pat- Ionian Sea, where the density was the Mediterranean always moved tern) are unusual. higher. This occurred toward the end against the wind-driven surface cur- Roule (19l4a, 1914b, 1917, of May and in the first half of June. rents - the "hydrodynamic" theory. 1924) believed that the bluefin were During June the continued warming This theory has received scant sup- pelagic or bathypelagic rather than reduced the density in the Ionian Sea. port. abyssal, but he felt that their migra- The tuna then returned to the deep Ninni (1922) discussed hypo- tions were restricted to the particular waters of the Tyrrhenian where the thetical populations and migrations basins of the Mediterranean which density was suitable for them. They of bluefin tuna in the Mediterranean they occupied. He (1924) studied went a few at a time, with the large in considerable detail. He believed temperature and salinity observations fish departing first, followed by that the Tyrrhenian bluefin were in- made during the season of spawning smaller ones up to September. These dependent of the Adriatic ones and assembly (May-June) in 1923 be- movements, which constituted the that both were independent of those tween southern France and Tunisia. "arrival" and "return" runs, were of the Aegean Sea, and that the last He found that the line of maximum based on the sensitive reactions of were at least partly independent of thermal increment ran directly from the fish. At the beginning of their those of the Sea of Marmara. Ninni southern France to Tunisia, fitting period of sexual maturity they un- assumed each group had its own well his (1917) hypothesis that when the derwent a reversal of their thermo- defined wintering area. He shared the bluefin were absent from the former tactic reaction. During the winter they opinion of Pavesi (1887) that the area, they were in the latter to spawn. chose a water temperature of about bluefin tuna wintered in deep waters. He found that these observations sup- 13.5-14.5°C, but with the approach ported his halothermic theory in re- of the spawning period, they became

105 thermophiles and sought surface wa- of the Italian boot on the north coast recaptures occurred after periods at ters of at least 18°C. The migrations (longitude 18°E) and nearly to Cape liberty of 65 days or less and within were probably provoked by the Misurata on the south coast (longi- distances of 150 km from the release "transgressions" of Atlantic water, tude 15°E) are indicated. points. One had passed through the which controlled their period and vol- Recoveries of single hooks or Strait of Messina into the Ionian Sea, ume, and were independent of gonad lures of central Mediterranean origin but the others had remained in the condition (Scordia 1932). suggested that bluefin moved freely southeastern comer of the Tyrrhenian The biometric studies of Arico between the various fishing centers: Sea. The unconfirmed recovery from and Genovese (1953) and Genovese Sardinia to Tunisia, Messina to a small tuna reportedly occurred (1957, 1958) supported Scordia's Sardinia, and Palermo, Sicily, to the within the general release area after a hypothesis of a distinct and separate Aegades Islands. More numerous re- time at large of about 18 months. Tyrrhenian-Ionian stock of bluefin ported findings showed movements The adult tuna had made a longer tuna. from the Strait of Messina to the "re- migration, from off Punta Raisi near Sella (1929a) maintained that the turn" traps along the southern part of Palermo at the end of May 1968, to Mediterranean bluefin could not be the east coast of Sicily, which cap- off Castellon, Spain, in mid-October separated into autochthonous stocks tured fish travelling southward along 1969 (Figure 71). Its weight was es- corresponding to the various basins, the coast. The only movements to timated as 28-30 kg when released, as proposed by Roule (1917) and other regions were a westward one and reported as 45 kg when recap- Ninni (1922). In addition to his from Messina to Arzeu, Algeria, and tured 17 months later. Atlantic-Mediterranean results, a longer migration to the east and The returns from small fish sug- Sella's (1927, 1929a) hook recover- north, from Sicily or Tunisia to the gest that their movements are quite ies indicated that bluefm tuna were upper Adriatic near Trieste, Italy. limited, but the times at liberty were constantly moving from one place to More dramatic findings resulted not sufficient, except in the case of another within the Mediterranean (see from six recoveries of very distinc- the one unconfirmed recapture, to Heldt 1930a, his unlabeled figure). tive and easily recognized lures used establish this as a definite tendency. These findings will be considered in only in the vicinity of Istanbul, Tur- The migration from Sicily to Spain terms of three general areas of ori- key. Two of these recoveries indi- by the larger fish, which was prob- gin: the western Mediterranean, cen- cated migrations to eastern Tunisia ably age 4 when released and age 5 tral Mediterranean, and the and southwestern Sardinia. Sella when recaptured, supports Sella's Bosphorus (Istanbul, Turkey). Hook (1929a) considered the finding offour (1929a) view that the mature bluefin items of Atlantic origin which were lures, each in a different individual travel freely about the Mediterranean, retrieved in the Mediterranean will caught in the same season and in the and refutes the concept of a distinct be considered with those of the west- only trap operating in the area around Tyrrhenian stock (Ninni 1922, ern Mediterranean, since the fish in Bengazi, Libya, as proof of the ar- Scordia 1938, Arico and Genovese which they were found could only rival of several schools coming di- 1953, Genovese 1957, 1958). Obvi- have entered the Mediterranean rectly from the Sea of Marmara and ously, much more tagging in various through the Strait of Gibraltar. the Bosphorus. Despite these impres- parts of the Mediterranean is needed Hook recoveries indicated extensive findings, the tendency to split to solve the complex problems ofthe sive eastward migrations within the the Mediterranean bluefin into sepa- migrations and stock structures in that Mediterranean. Numbers in paren- rate stocks continued for another 30 sea. theses following deduced migrations years. Sara (1964, 1973) studied the show the number of such migrations The taggings of blue fin in the behavior of bluefin tuna in the revealed, if more than one. Items from Mediterranean have not been suffi- Mediterranean extensively. He be- Malaga were recovered at Arzeu, Al- ciently numerous to answer the ques- lieved that age 0 bluefin made only geria, and near Tripoli, Libya. One tions which have been raised by de- very limited local movernents in the from Arzeu was found off southwest- ductive research. Arena and his col- area where they were spawned. As ern Sardinia. Another, from leagues marked 288 bluefin tuna off they grew larger, they migrated far- Philippeville, Algeria, was retrieved Sicily and the Aeolian Islands in the ther, but always within the same ba- at Sidi Daoud, Tunisia. More numer- years 1963-1968 (Arena and Sara sin, until they attained a weight of ous and extensive eastward migra- 1967, Arena and Li Greci 1970, about 100 kg and joined in the Atlan- tions were deduced from recoveries Arena 1971). Most of these were very tic-Mediterranean migration. The re- of fish with Atlantic hooks, whose small individuals (age 0, lengths 28- sults of tagging in the Mediterranean Mediterranean movements must be 42 em), but eight were adults weigh- cast doubt on the hypothesis of a considered to have begun at Gibraltar. ing 28 to 60 kg (ages 4-5). Returns separate Tyrrhenian-Ionian stock These retrievals occurred off Sardinia from four small fish and one adult (Scordia 1938, Arico and Genovese (10 + 1 probable), Sicily (5), have been recorded. The recapture of 1953, Genovese 1957,1958). Gallipoli, Italy southeast of Taranto another small fish was reported but Sara (\ 973) described the mi- (1», Tunisia (4 + I probable) and the tag was not returned. gratory and distributional patterns of Tripolitania (3). Thus movements The returns for small fish were bluefin in the Mediterranean in terms from Gibraltar as far east as the heel from releases in October 1967. The of the size groups. He used size

106 groupings recommended at the "Re- practiced in waters from south to limits of each basin. Apparently it union sur Ie Developpement et la southwest of the western end of Sic- was their contemporaneous presence Coordination de Programmes de ily. Dead bait was thrown into the in several localities, and their habit Recherches sur Ie Thon en water (chumming) to attract the tuna of remaining off this coast or that Mediterranee, Palermo 22-24/5/ to the surface. There they fed on small one, that, years ago, led to the con- 1967" (Anonymous 1968). These size live fish which had previously been cept of various populations differing ranges, which are quite similar to drawn to the boat by powerful lights. at the racial level. In the spawning those we have used, were as follows: The tuna were then vulnerable to cap- period, they approach the coasts, ag- large spawning tuna of over 150 kg, ture by seining. These catches took gregating with the schools of large place from late July until mid Sep- Atlantic tuna with which they can medium spawning and feeding tuna tember. mix only during the limited period of of 15 to 60-70 kg, Some large tuna remain in the reproduction. very small tuna and small tuna of up Mediterranean through the fall and Sara (1973) considers the small to 15 kg which have not yet at- winter in areas of rich and available and very small tuna next. In the tained their first maturity. food, such as the islands of the Tuscan months from August through all of Sara believed that most of the Archipelago, the area between the November, almost all of the Medi- large spawners which were observed Aeolian Islands and the Strait of terranean Basin is occupied by great from the end of April through all of Messina, the Dardanelles, and Port schools of young of the year. Re- • August, were of the same stock, of de Bouc in the Gulf of Lion. The maining for a few months along any which a portion, greater or smaller in numbers of these fish are in- coast, one can see them grow day by relation to certain oceanographic con- consequential in comparison with the day until in November they attain ditions, entered the Mediterranean to great mass of migrating fish which about 2 kg. After this, probably more spawn and, having accomplished this, occur in the period of reproduction. because of bad weather than because returned to the Atlantic to reconsti- The schools of large "Atlantic" oftheir departure, they are rarely cap- tute their biological reserves (Sec- tuna remain separate, according to tured. With the return of good tion VIClb). The numbers of tuna size offish, during the period ofmatu- weather, they are found again in the "hesitating" in the Ibero-Moroccan ration. During the time of actual late winter months in almost the same Bay and the volume of water enter- spawning, however, they mix tem- places where they had been seen ear- ing the Mediterranean determine how porarily with each other, and with lier, but now weigh 4-5 kg. The young many of these tuna enter in a given younger Mediterranean fish of ages tuna stay in the same areas, making year. These "arrival" tuna swim in 4-7. The latter at other times remain small movements in response to the surface layers, following the altogether aloof from the larger fish, meteoro-hydrological conditions and branches of the Atlantic currents or and, even during the reproductive in search of food. They remain sed- its counter currents. These usually processes, occupy other layers and entary until they attain their first follow routes quite similar to the areas when constrained together with sexual maturity, when they begin much-criticized ones proposed by them. their first migrations about the Medi- Cetti (1777). Displacements of these Medium and small fish weigh- terranean. branches of the currents by the winds, ing from 20 to 50 kg, with fringes of Sara's (1973) concept of the mi- toward or away from the traps, has a larger and smaller individuals, are gratory and distributional patterns of critical effect on their catches. seen and captured along the coasts of bluefin tuna in the MediteJTanean is These currents were illustrated the Mediterranean countries through- very similar to Sella's (1929a) in re- by Sara (1964, his Figure 1). The out the year (Sara 1973). These fish gard to the large blue fin, which both main current generally followed the school very strictly according to size. consider to be essentially migratory, African coast, bringing the tuna They are seen closer to the coast in and the immature fish, which both within range of the traps of Tunisia late summer and autumn, often on consider to be relatively sedentary. and Tripolitania. A west-flowing the surface in constant and furious They differ somewhat concerning the counter current brought the "arrival" pursuit of prey. They are present all behavior of the intermediate (me- tuna into the traps along the north year in certain locations near the coast dium) fish. Sella (\ 929a) felt that coast of Sicily from the east, rather where they can be observed and these were constantly moving, and than from the usual westerly direc- fished, even in bad weather, and the could not be separated into groups in tion. currents and geomorphology of the the various basins, whereas Sara According to Sara (1973), the bottom are favorable, as at the Straits (1973) believed that their aggrega- "return" tuna swim in deeper layers, of Bonifacio, in the Adriatic, at the tions tended to remain stationary for following the westward flow of the Aeolian Islands, at the Strait of considerable periods, and migrated Mediterranean water. This current Messina, at the Kerkennahs, and at only within the basin which they oc- flows southward and westward along the Dardanelles. cupied. Both scientists agreed that the east and south costs of Sicily, These fish have a different mi- knowledge of the spawning behavior where "return" traps were set until gratory pattern from the large ones of these intermediate bluefin was in- recent years. Sara (1973) found evi- and make limited spawning and tro- adequate. dence ofthis in the new night fishery phic (feeding) migrations, within the

107 The few details available on the parts of the bluefin tuna's range (Sec- into Portuguese waters. These fish trap fisheries of Tripolitania, and the tion VIClb). were 170 cm and 133 em long, re- ephemeral one in Cyrenaica These apparently inconsistent spectively. Seven of the 13 recap- (Bengasi) may provide clues in re- findings might be reconciled if it tures from the 172 fish released dur- gard to this important subject. Both could be shown that the larger fish in ing the "return" run occurred after Sella (1929a) and Sani (1973) cited the Sea of Marmara entered the Black from three to 23 days at large. One the later fishing of the Libyan traps, Sea to spawn, whereas the smaller recapture, as noted in part b of this compared to those in Tunisia, as evi- mature individuals reproduced offthe section, had "backed" to the east- dence of the eastward "arrival" run African coast. ward, well into the Mediterranean. of the bluefin from the Atlantic. Sella Another probable spawning area Another, recaptured where it had been (1929a) noted, however, that the fish for the intermediate bluefin is in the released three days previously, pro- taken in Tripolitanian and Cyrenaican Adriatic Sea, where these fish are vided no information. The remaining traps were medium and small. In a much more abundant than giants five made rather rapid migrations of later work, Sella (1932a) stated that (Section IVC6, Section VOl). This 90 to 100 nautical miles (167-185 the fish taken by the EI Mongar trap would be more in keeping with Sara's km) in from four to 11 days, travel- near Bengasi, Cyrenaica, although (1973) concept of limited spawning ling in the expected direction into, or mature, were too small to justify its migrations, within basins, for the approaching, the waters south ofPor- classification as an arrival trap. smaller mature fish. tugal. Three of these fish weighed Anonymous (1929b) described the The configuration of the Medi- from 70 to 90 kg, one weighed 270 fish which it caught in 1928 as very terranean and its approaches is such kg, and the weight of the remaining small ("picolissimi"). These data in- that many important problems could fish was not reported. These short dicate that the Libyan traps may have be solved quickly and definitively by term recoveries suggested that fish been harvesting the intermediate tagging, or by tracking with sonic tagged during the "arrival" period (Mediterranean) mature fish rather equipment. were more apt to deviate from their than the large (Atlantic) migratory expected migratory pattern than those d. Migrations and Stocks in spawning group. marked in the "return" period. This the Eastern Atlantic Another unsolved question con- is rather surprising, since the "ar- cerns the migration between the i. Large and Medium Fish rival" fish are believed to be concen- Mediterranean and the Black Sea. In addition to the four fish re- trating to spawn, whereas the "re- Hovasse (1927), Akyiiz and Artiiz captured in the Mediterranean (Sec- turn" fish are thought to be dispers- (1957) and IyigOngor (1957) all cited tion VICI b), 15 ofthe 312 fish tagged ing to feed. passages of maturing fish through the in the years 1960-1967 near Cadiz The approximate times at large- Bosporus into the Black Sea, and of have been recaptured in Atlantic wa- for the remaining six recaptures of spent fish in the opposite direction ters (Rodriguez-Roda 1969a). These fish marked in the "return" period (Section VDI). They differed, how- recaptures provided information on were 4 months for one fish, 10 months ever, in regard to the dates of these several migrations within the area of for three fish and 22 months for the runs. Hovasse (1927) and Iyigiingor the Ibero-Moroccan Bay trap fisher- other two fish. The longest Atlantic (1957) set the northward migration ies, and one to a more distant locality migration revealed by this set of re- in March and April, and the begin- (Figure 71). leases near Cadiz, about 370 nautical ning of the southward one in July. Since the periodic migratory pas- miles (685 km), was from off Barbate, Akyiiz and ArtOz (1957) postulated a sages through the trap fisheries ex- Spain, in August to off the Moroccan longer northward passage, starting in tend over only about four months, coast between Essaouira and Agadir April, peaking in July, and extending short-term tag returns are required to four months later (Figure 71). This into September, and a "return" run study them in detail. All of the six movement supported Aloncle's occurring from late October into No- recoveries from 140 fish tagged dur- (1964) hypothesis of seasonal migra- vember. ing the "arrival" period occurred tions of bluefin tuna between waters Sella (1929a), on the other hand, within 85 days of the releases. As off southern Morocco and the Ibero- cited what he considered to be clear noted in part b of this section, three Moroccan Bay. This fish, however, evidence of a massive migration of of these recoveries took place in the weighed 175 kg, considerably more tuna from the vicinity of Istanbul to Mediterranean, representing a con- than the group which Aloncle was spawning grounds off Cyrenaica. tinuation of the expected easterly discussing. Four lures, of special types used only movement. One of the other recover- All of the long-term (10 months in the Bosporus and its approaches, ies was irrelevant, since the fish was or 22 months at large) recaptures of were retrieved from the few hundred recaptured almost immediately by the fish marked during the "return" run tuna caught during the 1929 season trap from which it had been released. were in traps fishing the "arrival" in the EI Mongar trap, the only one The other two recoveries, however, passage. Three recaptures occurred set in Cyrenaica. Such a migration indicated rather rapid "backward" near Larache, Morocco, about 40 to would be consistent with SelIa's (westward) migrations of 79 miles 60 nautical miles (74-112 km) south (I 929a) hypothesis of spring spawn- (146 km) in one day and 100 miles of the release point, one off Portugal ing concentrations in the southern (185 km) in two days, respectively, and another at Sancti Petri, about 100

108 nautical miles (185 km) and about 20 250 cm long) bluefin tuna in August the Norwegian coast ceased and most miles (37 Ian) west of the release and September 1957-1962 near of these fish followed the southward point, respectively. These long-term Bergen, Norway. Six of these fish migratory route previously used by recoveries suggested that the Moroc- have been recaptured near Cadiz, medium-sized fish (Hamre 1965). can and Iberian trap fisheries in the Spain, and 26 in Scandinavian wa- Tiews (1964) and Hamre (1965) Atlantic harvested the same stock. ters (Figure 72 ) (Hamre 1965 and agreed, on the basis of the locations Comparison of the return rates personal communication). Four of the and periods of fishing and the sizes and times at liberty for fish tagged Spanish recaptures occurred after less of fish taken, that the large bluefin from the "return" run (7.6%, five re- than 10 months at liberty ("direct" which had arrived in July and trav- captures after 302-683 days at lib- migrations). The other two took place elled northward along the Norwegian erty) with those for fish marked dur- 23 and 45 months after release, coast from Bergen eventually left that ing the "arrival" run (4.3%, no re- respectively. If we exclude nine of coast and migrated southward into captures after more than 85 days at the local returns which were recov- the North Sea. There they were vul- liberty) suggests that fish tagged from ered in the season of their release, nerable to the German and Danish the "return" run were more viable and thus had no opportunity to emi- fisheries (Section IVC5 b and c). than those released from the "arrival" grate, 26% of the returns were from When these large fish reversed their run. Spain, as against 74% from local migration route in 1963, predomi- Giant and medium-sized bluefin waters. Bluefin were tagged off Nor- nantly following the Norwegian coast occurred in Scandinavian and North way in each of the years 1957-1962, southward rather than northward, the Sea waters during the summer and but the tags used in 1957 were evi- North Sea fisheries disappeared fall. It was generally believed that dently defective and produced no re- (Hamre 1971, Tiews 1975). these came, at least in part, from the turns at all, and only 13 fish were The local tag returns (Hamre "return" run which was fished by the marked in 1962. One more of the 1965, personal communication) con- traps off southern Spain and Portu- fish tagged off Norway in each ofthe firmed migratory patterns (Figure 73 gal in July and August (Sella 1929a, other years was subsequently recap- ) in Norwegian waters which Hamre Sara 1964). Le Gall (1929) projected tured off Spain. These results sug- (1962) had also deduced from stud- a northward migration route west of gest strongly that substantial num- ies of the size composition of catches. Ireland and north of Scotland into bers of the bluefin tuna which oc- The bluefin tuna reached the coast at the North Sea and the Scandinavian curred off Norway in summer and about 62°N latitude. The larger indi- waters, on the basis of observations early fall also occurred off southern viduals, which arrived in July, mi- of tuna from fishing boats along the Spain in spring and early summer, grated northward and the smaller way. Sella (1929a) identified a hook presumably there to spawn. Studies ones, which arrived in August, mi- found in a bluefin tuna caught in of the size composition of the land- grated southward. One of the latter Oslo Fjord, Norway, as of the type ings in Norway and southern Spain which had been tagged near Bergen used in the Bay of Biscay. This find- (Hamre et a!. 1968), however, indi- was recaptured off the island of ing supported the concept of a north- cated that the fisheries in these two Anholt in the Kattegat. In addition to ward migration of bluefin tuna from areas did not harvest the same stock the nine returns in the release season, Iberian waters to those off in every year. In 1955 through 1960, nine tags were recovered after about Scandinavia. Le Gall (1929) also the size composition of the Norwe- one year at liberty, three after about noted indications of a southward m i- gian and Spanish catches were quite two years, as well as single ones from gration passing north and west of the similar, but in 1961 through 1964, fish which had been at large for about British Isles in the fall. Le Gall (1927, they were quite different. In 1965 three, five, six, seven and eight years. 1929) noted that the presence of blue- they were similar again. Hamre et a!. In recent years, most ofthe bluefin in the North Sea was controlled (1968) attributed these changes to a fin tuna in Norwegian waters, all of by influxes of Atlantic or Atlantic subdivision of the northeast Atlantic which have been very large, have slope waters with salinities of about tuna population into two contingents left there early in the fall. Prior to 35 0/00. These waters entered the with different migratory habits in 1963, when medium fish were abun- North Sea from the north. Records of 1961 through 1964. dant there, many of these fish did not bluefin in the English Channel were Although it has not been dem- depart until late autumn. The ensu- scarce, although fish occurred fre- onstrated by tag returns, Hamre ing migration of the large bluefin quently off its western entrance, and agreed with Le Gall (1927, 1929) apparently takes them north and west off the western end of Cornwall. Le that the bluefin entered the North Sea of the British Isles to their wintering Gall (1927) noted that these fish were and Scandinavian waters from west area. This probably lies between lati- in the feeding phase, and speculated and north of the British Isles, rather tudes 25°N and 400N and between that they had spawned in the Ibero- than through the English Channel the African and European coasts and Moroccan Bay. (Figure 73). longitude 35°W (Shingu et al. 1975, The accuracy of this assumption After the disappearance of me- Fisheries Agency of Japan 1976). The was proved by the tagging experi- dium-sized bluefin from the Norwe- size distribution of the fish in the ments of Hamre (1965). Hamre gian fishery in 1963, the northward area is not known. Aloncle (1964), tagged 242 medium and large (150- migration of the giant bluefin along however, reported that small to me-

109 dium fish occurred between the Ca- grounds. Most of the large !ish and while en route to the Bay of Biscay nary Islands and Morocco in winter. some of the older mediums partici- (Aloncle ]964). Others may spawn Many medium and some large pate in the "arrival" run, assembling after arriving there (Cort 1977), thus bluefin are captured in the Bay of in the Ibera-Moroccan Bay in May actually spawning in their feeding Biscay from mid-July to mid-August, and June. One contingent of them, area. or early September (Creac'h 1952, mainly the individuals weighing less Most of the large "return" fish Le Gall 1954, Bard et al. 1973, Dao than 150 kg, presumably spawns migrate from the Ibero-Moroccan and Bessineton 1974, Cort 1975, there, along with a portion of the Bay around the British Isles to their 1977). Some of the smaller fish may larger fish. Apparently many of the summer feeding areain Norwegian spawn on their arrival in the Bay latter, however, enter the Mediterra- waters. Many of the smaller ones, (Cort 1977), but this is primarily a nean, spawn there in June or early including most of those wh~ch have feeding concentration. Where these July, and make a "return" run into spawned in that Bay, proceed to the blue fin go after they leave the Bay of the Atlantic in July and August. Most Bay of Biscay, but others may join Biscay is uncertain. Cort (1976) con- of the larger fish which have re- the concentration off the central Mo- jectured that those in age groups 6 to mained in the Ibero-Moroccan Bay roccan coast. This gathering is occa- 9 continued their northward migra- also join this "return" run. sioned when the impingement on the tion to Norwegian waters, whereas Some of the smaller individuals north em coast of Morocco of a tongue those in age groups 4 and 5 followed may spawn off the Moroccan coast of warm (over 21 °C) tropical water a different, probably more southerly, route. The migration of age groups 6-9 to Scandinavian waters may well have taken place in years prior to 1963, but fish of these ages have not been important in the Norwegian catches since then (Hamre 1971). The European landings of medium bluefm in the Bay of Biscay lIIII'60--JlIII '61 have increased markedly since 1973, perhaps in consequence of substantial fishing effort by Japanese longline vessels in the area (Cort and Cendrero 1975, Cort 1976, Fisheries Agency of Japan 1976, Shingu and Hisada 1976). It is unfortunate that adequate size composition data for Bay ofBis- cay landings in the 1960s are not available. It would have been of interest to note whether the departure of the medium fish from the Norwe- gian fishery in 1963 through failure of recruitment (Hamre 1971) was re- flected by any increase in their availability in the Bay of Biscay. The medium and large bluefin which leave the Bay of Biscay in August or early September presum- ..- ably reach the wintering area described above in late fall or early LEGEND ° "ELEASE LOCALITY winter, but their whereabouts in the • RECAPTURE LOCALITY - • - HOOK RECOVERY meantime is unknown. Possibly some -- LESS THAN 10 MONTHS AT LIBER - - - MORE THAN to MONTHS AT LIBERTY ofthemjoin the concentration off the R&\~~~4DATE (SI RE~.."~~6DATE (SI central Moroccan coast, along with t NUMBER OF FISH IF MORE THAN ONE others which may have gone there directly after spawning in the Ibero- Moroccan Bay (Aloncle 1964). In April the medium and large bluefin begin to migrate from their Figure 72. Geographic distribution of blue fin tag release and recapture data from wintering area to their spawning Norwegian tagging studies and hook recovery data in thc eastern Atlantic.

110 from offshore inhibits the further tured in the Bay of Biscay in June- Local returns showed two south- progress of some groups of small and August 1973. These important results westward movements from the medium tuna travelling northward indicate that both the minor fall fish- Larache-Casablanca area toward Cap from the wintering area. These fish ery off the west coast of Portugal and Blanc in August-September 1972 and eventually find themselves in the the much more important one which two northward migrations from off cooler upwelling waters off the cen- takes place in the Bay of Biscay dur- Agadir to off Essaouira in Novem- tral Moroccan coast, but completely ing the warm season draw recruits ber-December 1972. surrounded by tropical water. Most from off the Atlantic coast of Mo- Lamboeuf (1975), considering of them stay in this cool water rather rocco. These few returns suggest that these results and observations of the than continuing northward through fish recruit to the former fishery at movement of the fishery and the sizes the warmer water (Aloncle 1964). age 1 and to the latter at age 2. These of fish caught, formulated the fol- The return to summer feeding ages of recruitment are in accord with lowing hypothesis: areas completes the migratory cycle the age groups which have been pre- Bluefin spawned off Morocco by of the medium and large bluefin of dominant in the landings of the re- the adult "arrival" tuna in spring or the eastern Atlantic. The hypotheti- spective fisheries. The tendency for early summer remain offshore in fa- cal three phase migration is compli- the maximum catches of vorable waters (18°C-22°C). They cated by the entrapment of some me- "cachorretas" (age I bluefin) in the occasionally approach the coast when dium fish off central Morocco, and Portuguese trap fishery to have oc- hydrological conditions allow this. the entry oflarger fish into the Medi- curred in late August suggests that Having attained I year of age and 50 terranean to spawn. the indicated migration from offMo- to 60 cm in length, they frequent the rocco in summer to off western Por- coast from June through August, ii. Small Fish tugal in the fall may sometimes have moving from north to south during Thirty-four small bluefin tuna passed along the south coast of Por- this period. They then disappear, hav- have been tagged in the Bay of Biscay tugal en route. ing been driven offshore by the cold and off Portugal since 1960 (A loncle waters in the Safi-Essaouira region, 1973). Three of these were recaptured locally, and two off the northeastern United States. One of the local returns was from a small bluefin tagged off Cape St. Vincent (southwestern comer of Portugal) in early June and recaptured in the Bay of Biscay 83 days later (Figure 74). This migration supports Aloncle' s (1964) hypothesis that small bluefin migrate seasonally from the Ibero- Moroccan Bay in spring to the Bay of Biscay in summer. The transatlantic returns will be discussed in part 3 of this section. The results of tagging off the Atlantic coast of Morocco (Lamboeuf 1975) also support Aloncle's (1964) NORWAY theory. During 1972 and 1973, 63 bluefin, 41-73 em long, were tagged arid released there: 15 in June, one in July, 25 in August and 2 I in Novem- ber. Eleven returns resulted, includ- ..': ing five from Moroccan waters and ~. six from other areas (Figure 74). During 1973 two fish, of which one had been marked in June and the other in August (at ages of approxi- NORlll SEA mately I 1 and 14 months, respectively), were recaptured off the southwestern coast of Portugal in October and September, respectively. Four O· 10· others, of which three were tagged in August I972 (at ages of about 13 Figure 73. Possible paths ofbluefm tuna entering the North Sea and Scandinavian months) and one in November 1972, waters from west and north of the British Isles, rather than through the English (age about 17 months) were recap- Channel.

III interrupted by local hydrological conditions, and the mature individuals are incl ined toward the three-part m i- gratory pattern proposed for the older age groups. iii. Very Small Fish Eastern Atlantic· bluefin (apply- ing this term to individuals which are recruited to stocks in the eastern At- lantic asjuveniles) are hatched mainly 40" in the Mediterranean Sea and/or the Ibero-Moroccan Bay. Those born in Xl '72--'IlI'73 the former area, however, would have to pass through the latter to reach LEGEND their nursery areas. Supplementary o RD.EQf LOCAliTY • Rl!:c;APTU"! LOCALITY hatching may extend to the area be- - LESI THAN to MONM AT LIBERTY --- MOllE. 'HAN to MONTH! AT LI8[ItTY tween the Canary Islands and Mo- "'\f~~,~T((S) .• ~.::TEtS) • HUMin Of FISH, IF MORE THAlli Oh( rocco, and also into the Bay of Biscay . The principal hatching occurs from

NorE-o LIAi£$ JOININ6 /rELEASES AND 1t£1VJIWS about the middle of June to about the AII£ DIAfiRAMMATIC AND AItE Nor INTENDED TO REPRESENT MIGIfA'tO!t ROIITCS. middle of July, with reproduction by the smaller individuals occurring up to the end of July or later. By mid- o November, when they are about 40 cm long, the bulk of the new-born Figure 74. Geographic distribution of bluefin tag release and recapture data from tuna have converged from their vari- Moroccan and Bay of Biscay tagging studies, ous birth places to concentrate off the Atlantic coast of Morocco, where they complete their first year of life in the following June or July. only to reappear in the Bay of Agadir zone between the Canary Islands and in November and December. These Morocco, but the total winter habitat 2. Western Atlantic bluefin which have attained a mean is probably much larger, with the fish a. Introduction length of 67· cm· then undertake a spreading over greater areas as they longer migration, passing along the attain older ages. Tag returns, data on the fisher- Portuguese coast and penetrating Age 3 and 4, and older, bluefin ies, and knowledge of oceanographic deeply into the Bay of Biscay, move northward again in the spring; conditions must be used in combina- In certain years, as in 1973, when probably the majority of them even- tion to establish hypothetical migra- the cold waters of the central sector tually enter the Bay of Biscay. Many tion patterns for bluefin tuna. Since extended far offshore, the tuna may of the older individuals in this group 1954, about 2,760 giant, 490 me- have migrated earlier in the season, are mature. Some ofthese may spawn dium, and 14,630 small bluefm have bypassing the Agadir area. during this northward migration, and been tagged in the western Atlantic and 63, 9, and 3,000 returns, respec- These results of tagging offPor- others may split off from it and spawn tugal and Morocco and Lamboeufs with the larger fish in the Ibero-Mo- tively, have resulted. These returns (1975) hypothesis explain Furnestin roccan Bay. During late summer and have not only provided important in- and Dardignac's (1962) observation fall, considerable aggregations of formation on movements within the that young bluefin become scarce small and medium bluefin occur off area, but have also revealed surpris- along the Moroccan coast in Novem- the central Moroccan coast, as noted ing migrations to distant regions. ber, when they have attained a length previously. Some of these fish may Extensive data on the coastal and oce- of 64 cm, and confirm Aloncle's have been trapped there by a warm anic fisheries are available (see Sec- (1964) hypothetical migration of water mass during their northward tions IYC2 and Iye3) to comple- young bluefin from Moroccan wa- movement and others may have mi- ~ent the pattern discl~sed by tag- ters to the Bay of Biscay, grated there after spawning in the gmg. Also, comprehenSive works on After feeding in the Bay of Ibero-Moroccan Bay. Most of the the oceanography of the Atlantic, Biscay through the remainder of the small blue fin which have spawned with detai Is of its circulatory system, warm season, the age 2 fish depart, there, however, probably proceed to have been published (Sverdrup et al. along with fish a year or two older, the Bay of Biscay, entering it during 1942). Those concerning the Gulf mainly in October. Their next desti- the last half of July or early August. Stream system (Fuglister and nation is their wintering area, which Thus the hypothetical two-part mi- Worthington 1951 , Yon Arx et al. is little known. There is a wintering gratory pattern of this group may be 1955) are of special interest in relation to the distribution and migra- ] 12 tions of blue fin tuna in the north At- in regard to body condition. The fish and IVC3). The records of occur- lantic (SelIa 1931, Rivas 1955, Squire taken off New England in the begin- rences during the cold season (No- 1963). Since the economic impor- ning of the season were similar in vember-April), when their where- tance of the species in the western body proportions to those taken in abouts had previously been virtually Atlantic has been slight until recent the Straits of Florida. As the season unknown, were especially valuable. years, the history of research on its advanced, however, the fish off New This information has been used in migrations there is brief in compari- England fed heavily and gained conjunction with tagging results in son with that in the eastern Atlantic weight rapidly. Therefore the fish developing new hypotheses on the and the Mediterranean. taken there in August, September and migrations of the species (Mather October became progressively 1969, 1974, Mather et al. 1974). b. Large Fish heavier in proportion to their length Continuous tagging of western Few deductions about the mi- than those taken in the Straits of Atlantic bluefin began in 1954. Since gration of large bluefin tuna in the Florida. The ratios of their girth and then, about 1,100 giant fish have been western Atlantic have been published. depth to their length consequently marked off the northwestern Baha- The summer and early faIl occur- also became greater than the corre- mas (Straits of Florida) and 15 of rences of blue fin tuna off northeast- sponding ratios for fish taken in the these fish have been recaptured over ern North America (off the United southern area. a very extensive area - four off States coast from New Jersey to Rivas (1955), in a similar study, northeastern North America, two off Maine, and off Nova Scotia and New compared the morphological charac- eastern South America, and nine off Brunswick in Canada) have long been teristics of samples of blue fin tuna of Norway (Table 28) (Mather 1962, known (Farrington 1939). A periodic similar sizes taken in the Straits of 1969; FAO 1972, Mason et al. northward migration of "giant" blue- Florida in May 1952-1954 (19 speci- 1977).Cooperating sport fishermen fin through the Straits of Florida mens) and at Wedgeport, Nova provided the effective tagging in this (mainly along the northwestern edge Scotia, in October 1952 and August effort. A few fish have been marked of the Great Bahamas Bank near Cat 1953 (nine specimens). He found no during exploratory fishing cruises in Cay and Bimini) was discovered by significant differences between these this general area, but none of the tags sport fishermen in the 1930s and it samples, except those attributable to have been returned. was soon concluded that these fish the normal seasonal change in body The fourretums offNorth America were among those which subse- condition experienced by bluefin were from off Maryland to off the Nova quently occurred off northeastern tuna. These fish lost considerable Scotian banks (Figure 76); only one North America in summer and early weight during the spawning process was from an area known as a tuna fall (Farrington 1939, Mowbray and related migrations, then fed so fishing ground. This return was from 1949). heavily during the summer and early a giant released in early June 1973, At the Oceanic Fisheries Con- fall that their length-weight ratio was in the Bimini-Cat Cay area (north- ference held at the Bermuda Biologi- at a minimum in September-Octo- western Bahamas) and recaptured cal Station for Research, May 28-31, ber. The lean condition of the fish about 18 nautical miles (33 km) 1951, (transcript of tape recordings taken in the early part of each season northeast of Gloucester, Massa- available at Woods Hole Oceano- at Wedgeport was consistent with chusetts, a well-known center for graphic Institution) Schuck and their having come from the Straits of small boat tuna fishing, in early July Mather presented their views on sev- Florida. In addition, Rivas showed 1974. Since it had been at liberty for eral aspects of the biology of blue fin that the times of arrival of giant blue- 13 months, this was not a "direct" tuna in the western North Atlantic. fin tuna off Cape Cod, Massachu- migration. If it is regarded as a sec- They described the behavior of the setts, and Wedgeport were consistent ond retracing of an annual migratory giant bluefin tuna in the Straits of with the time of departure and esti- cycle, however, the fish would have Florida as observed during flights mated average speed (3.5 knots, or passed through the Straits of Florida made with L. R. Rivas in U.S. Coast 6.5 km/hr) and direction of travel of again in Mayor June 1974, and its Guard aircraft. These observations the individuals passing the Bahamas. ensuing migration would have fitted confirmed that the visible schools Thus he presented a case, which he the proposed pattern. The other three were virtually all travelIing north- considered strong, but not conclu- recaptures were incidental or acci- ward, as reported by the sport fisher- sive, for a northward migration of dental catches by vessels fishing for men. Schuck and Mather also showed giant bluefin from the Straits of other species. While they could be that the times of the passage of the Florida in May-June to New England interpreted as representing incom- giant tuna through the Straits of and Nova Scotia waters in summer plete migrations toward the New En- Florida and their arrival in New En- or early fall. gland or Canadian feeding areas, gland waters were consistent with a Exploratory and commercial there is an element of doubt in each migration between the two areas. Fi- long line fishing has provided impor- case. One return was from a fish re- nally, they presented preliminary re- tant information on the temporal and captured about 48 nautical miles (89 sults of biometric studies which areal distribution of bluefin in the km) east-southeast of Ocean City, showed that the fish taken in the oceanic waters of the western Atlan- Maryland, in April 1973, 23 months Straits of Florida were similar to those tic since 1956 (see Sections IVC2 after it had been released off the taken in New England waters, except

) 13 northwestern Bahamas in May 1971. This migration of at least 6,600 nau- Cape Hatteras in May and June. In The inshore location of its recapture tical miles (12,250 km) is the longest July, the longline catches of large suggests that it might have eventu- ever recorded for an Atlantic bluefin. fish diminishes. The capture off ally entered New England or Cana- These surprising recoveries pro- Recife of a giant bluefin which had dian coastal waters. Its recapture date, vided the first clues to the relation- been tagged off the Bahamas in- April 4, however, indicates that, if it ships between the bluefin tuna stocks creases the probability that a group had come from the Straits of Florida, of the North and South Atlantic. of large fish does actually migrate it must have left there in March, well Catch records of the Japanese from off the Bahamas in May-June ahead of the usual May-June pas- longline fishery (Fisheries Agency to off Cape Hatteras by early July, sage. The other two recaptures oc- of Japan 1965, 1966, 1967a, 1967b, thence to various summering areas curred .in offshore waters, from 40 to 1968,1969,1970,1971, 1972, 1973) farther nOlth (Figure 75), and south- 65 nautical miles (74 to 120 km) out- show that, in some years, an area of ward in the fall to wintering areas side the 2,000 m contour. One fish, intensive bluefin fishing develops in around the Antilles and off South which was recaptured 135 nautical March and April off easternmost Bra- America. It had been generally be- miles (250 km) southeast of Nan- zil, moves northwestward toward the lieved (Wise and Davis 1973) that tucket Island, Massachusetts, in June Bahamas and then northward to off bluefin tuna concentrations northof 1970 had been released four years previously, in May 1966, in the Cat Cay-Bimini area. The fourth tuna had been released in the same locality in early June 1970, and was recaptured Table 28. Releases and returns for giant bluefin tuna (over 120 kg) tagged off the just 30 days later 100 nautical miles Bahamas by year of release, months at large, and area* of recapture. Also shown (185 km) southeast of Sable Island, is the estimated percentage of German North Sea bluefin tuna catches in late off Nova Scotia. Thus it had trav- season (September 15 - October 31) recruited from the western Atlantic (Tiews elled at least 1,500 nautical miles 1964). (2,800 km) in a maximum ono days, requiring a minimum average speed Year Releases Returns by Month at Large % of 2.1 knots (3.9 km perhr). It is 0-5.9 6-17.9 18-29.9 30-41.9 42-53.9 78 - 89.9 uncertain whether these fish, had their journeys not been terminated, would have proceeded to the feeding 1954 21 0 0 0 0 0 0 8 grounds off the American coasts, 1955 14 0 0 0 0 0 0 4 completing the hypothetical migra- 1956 41 0 0 0 0 0 0 6 tion, or continued across the ocean to 1957 0 0 0 0 0 0 0 0 Norwegian waters, as so many other 0 bluefin released off the Bahamas have 1958 0 0 0 0 0 0 7 done. It is widely believed, however, 1959 25 0 0 0 0 0 0 0 that these animals have a strong ten- 1960 13 0 0 2N 0 0 0 II dency to foIlow favoring currents 1961 34 2N 0 0 0 0 0 33 when migrating (Sella 1929a, Rivas 1962 45 IN 0 0 0 0 0 2 1955, Lozano Cabo 1958, 1959b; Sani 1964, 1973; Rodewald 1967). 1963 147 0 0 I B 0 0 0 Since both of these fish were recap- 1964 41 0 0 0 0 0 0 tured far north of the Gulf Stream, 1965 54 0 0 0 0 0 0 which would have favored a migra- 1966 105 0 0 0 0 IA 0 tion to Norway, it seems more probable that they would have proceeded 1967 82 IN 0 0 0 0 0 to the nearby American feeding 1968 57 0 0 0 0 0 0 grounds than that they would have 1969 50 0 0 0 0 IB IN wandered out into the less produc- 1970 182 IA 0 0 0 0 tive waters of the open ocean. 1971 49 0 0 IA 0 0 Two giant bluefin tagged off the northwestern Bahamas have been re- 1972 . 32 0 IN 0 0 0 captured in the South Atlantic (Table 1973 47 0 lA, 1 N 0 0 28, Figure 75) (Mather 1974). One 1974 31 0 0 0 fish was marked in May 1963 and 1975 18 0 0 recaptured southeast of Recife, Bra- zil, in March 1965. The other fish, 1976 5 0 released in June 1969, was recap- Areas: A = Northeastern North America, B = Brazil and Argentina, N = tured off Argentina in February 1973. Norway.

114 ·" '. ~...\; .. , LEGEND

~ 0 AE1.EA8E LOCALITY • fW!CAPTI.IE LOCAUTY - LESS TtWf 10 MONnlS AT L1.wrt ---MCRE lHAH to UON11fSAT UIlEMY IlEL£ASE Dl\tEls) RECAPTIIIE Dl\1aS1 (21 VI '&4 VII· VIII '66 t IUIIEIl at' I'ISH '" _ 11WI OM£ m.UWI./IJIIIIIII.,r _ NW • ..,tl~ •••• "",.~ ..~:~:_~--j::--~.,,\~ •• ;,0 ••••• ..-' •••• w: \. " =:.., * ',' .':......

40·

TA(l MTUlNI $tIOWINI WQT'EAST ATlANTIC CMmlINOS IIY SlMLL lIl.U91N TUNA

(II VII'&<1-. VII ·YIII '59 (MI VlI·,\IIU'.e-. I/lHI '. "I VIII'U-. VII-VIII'67 (lll VII-VIII'" ··y,:,x'67 VlII'e··VII' •• l!t VII-VIII·•• ··vnHx·1t VII'• ., --1I '.1 YlI',7-VlI'U ','. VII '16-VIH''I'O (21VlI'n'-VII'''' i~··':. VII '71-VII'79 VII'1$--VMI'19 Ylll' 'PI - VIII '." :;.

Figure 75. Geographic distribution of bluetin tag release and recapture data illustrating transatlantic and transequatorial migrations.

latitude 20oSconsisted mainly of At- had been tagged off the Bahamas in- The nine recoveries in Norwe- lantic bluefm tuna T thynnus thynnus, dicates that the already tremendous gian waters from the releases in the and that those south of 200S con- migratory circuit suggested above for Straits of Florida will be discussed in sisted mainly of southern bluefin Atlantic bluefin occasionally extends part 3 of this section. tuna, T. maccoyii. The recapture off much farther south, well into the habi- Giant bluefm tuna have also been Argentina of a giant bluefin which tat of tlle southern bluetin. tagged successfully during the sum-

]]5 Table 29. Releases and returns for giant bluefm tuna (over 120 kg) tuna tagged in Gulf of St. Lawrence had been at St. Margaret's Bay, Nova Scotia, by year of release, months at large and arca* of liherty for 49, 60 and 63 months. recapture. These six migrations were therefore "indirect". The recaptures off New Year Releases Returns by Months at Large Total England occurred in June (1 recap- 0-5.9 6-17.9 18-29.9 30-41.942-53.9 54-65.9 ture) and August (3 recaptures); the one at Wedgeport occurred in Sep- tember. Those in the Gulf of St. 1963 18 0 0 0 0 0 0 0 Lawrence occurred in July (1 recap- 1964 6 0 0 0 0 0 0 0 ture), August (2 recaptures), Septem- 1965 52 2L IL 0 0 0 0 3L ber (3 recaptures) and October (1 recapture). The two local recaptures 1966 71 0 2N 0 0 0 0 2N after a winter at liberty took place in 1967 193 5L,IW 0 IN 0 0 0 7LWN August and October. 1968 0 0 0 0 0 0 0 0 Sport fishermen cooperating 1969 15 IL 0 0 0 0 IG 2LG with United States and Canadian pro- 1970 3 0 0 0 0 0 0 0 grams have tagged 962 giant bluefm in eastern Newfoundland waters, and 1971 45 0 0 0 IN IG IG 3NG of these nine tags have been returned 1972 12 0 0 0 0 0 0 (Table 31). Four of these were re- 1973 0 0 0 0 0 0 covered locally, but five were re- 1974 8 0 0 0 0 turned from other areas (Figure 77). The longest migrations recorded were 1975 148 3G IL 4GL from Notre Dame Bay, Newfound- 1976 12 IG IG land, in August 1970 and 1971, to Cape Cod Bay, Massachusetts, in July *Areas: L = Local, G = Gulf of St. Lawrence, N = New England, W = 1974, and October 1973, respectively. Wedgeport, Nova Scotia These two fish had moved nearly 1,000 nautical miles (1,850 krn). Two

mer off northeastern North America. 100· 95· 90· 85· SO· 75· 70· 50· 50· Since 1961, 583 giant bluefin tuna LEGEND have been tagged and released from o RELEASE LOCALITY • RECAPTURE LOCALITY traps in St. Margaret's Bay near o RHURN NUMBER Halifax, Nova Scotia, (Beckett 1970, 45· Caddy and Burnett 1975, Burnett o~ * ~~:~~f* :~~~=• :3l: '66 Ct3511 •. ) :m '70 194k9- 1977), and 22 of these tags have been 2 1lI "0 120._ •.1 :m 'ro 179_•. 3 % '7' net kgI JE 'n !'Io.,. returned (Table 29, Figure 78). Ten •• :m: '7~ (Zl6111) lID:'7. a6lr.9 40· 5 Jt '7' '.82',.) m '15 25011.9. of the recaptures were local (in St. 6 JI1 ·7~(2951l1.) III '77 2tiOCIll. * WEIGHTS a.AE fOR WH

116 Table 30. Release and recovery data for bluefin tuna tagged in S1. Margaret's Bay, Nova Scotia and recovered elsewhere, with size at recapture and months at liberty.

Return Release Recapture Number Location Date Location Date Weight Liberty

S1. Margaret's Bay VIII -1966 Cape Cod, Massachusetts VIII-I 967 - 11.3 44° 37' N 64° 00' W 2 S1. Margaret's Bay VII -I 966 Cape Cod, Massachusetts VIII-I 967 - 13.5 44° 37' N 64° 00' W 3 St. Margaret's Bay VII-1967 Wedgeport, Nova Scotia IX-1967 - 1.6 44° 37' N 64° 00' W 4 S1. Margaret's Bay VII-1967 Cape Cod, Massachusetts VI-1969 - 23.3 44° 37' N 64° 00' W 5 S1.Margaret's Bay VIII-1969 Prince Edward Island, Canada VII-l 974 278 60.0 44° 37' N 64° 02' W 46° 40' N 63° 50' W 6 S1. Margaret's Bay IX -1971 Cape Elizabeth, Maine VIII-l 974 - 34.7 44° 37' N 64° 03' W 43 30' N 70° 06' W 7 St. Margaret's Bay VII -I 971 Chaleur Bay, New Brunswick VIII-I 975 412 49.8 44° 39' N 63° 59' W 48° 08' N 64° 56' W 8 St. Margaret's Bay VI-1975 Prince Edward Island, Canada IX-1975 388 2.4 44° 37' N 64° 02' W 47° 06' N 63° 55' W 9 S1. Margaret's Bay VI-197 5 Prince Edward Island, Canada IX-I 975 301 2.7 44° 30' N 63° 56' W 46° 29' N 62° 01' W 10 St. Margaret's Bay VI-1975 Prince Edward Island, Canada IX-1975 374 2.8 44° 36'N 64° 03' W 46° 31' N 62° 07' W 11 St. Margaret's Bay VII -1971 Prince Edward Island, Canada X-1976 427 62.8 44° 38' N 63° 59' W 46° 28' N 62° 44' W 12 St. Margaret's Bay VI-1976 Chaleur Bay, New Brunswick VIII-l 976 395 2.1 44° 38' N 64° 00' W 48° 09' N 64° 54' W

others travelled from Notre Dame western Florida (Figure 79). All the Nova Scotia to New England and Bay to St. Margaret's Bay, Nova giant bluefin marked in New England from Newfoundland to Nova Scotia Scotia, one in 47 months and the and Canadian waters were tagged or New England have occurred within other in 59 months. One tuna moved during the summer-fall feeding sea- a single season. from Notre Dame Bay in August 1972 son (July-October), and all but two The two returns from outside Ca- to the southern extremity of the Grand of the recaptures occurn:d in the same nadian and New England coastal wa- Banks in December 1973. The times general area and season. This group ters provide more significant indica- at liberty for the recaptured fish var- of recaptures shows that large blue- tions of migratory patterns. The De- ied from a few days to nearly six fin move freely within the waters be- cember recapture, at the southern end years. tween Cape Cod and Newfoundland, of the Grand Banks, of a giant blue- Cooperating sport fishermen also and return to them year after year. fin which had been tagged in New- mQrked 117 giant tunas in New En- Evidently fish off northern New foundland coastal waters 16 months gland waters, and 17 returns have England and off Canada are of a previously may show the initiation resulted (Table 32). All but one re- single stock, or of stocks which are of a southerly migratory route even capture were local, after periods of only partially separated. The only though it was not a direct migration. from a few days to about three years. "direct" migrations, however, have The migration from New England The exception was a fish released been one from St. Margaret's Bay to coastal waters in July to the Gulf of July 22, 1974, in Massachusetts Bay Wedgeport and four from that Bay Mexico in the following May pro- off Boston and recaptured May 13, into the Gulf of St. Lawrence. None vides the first definite and "direct" 1975, in the Gulf of Mexico off south- of the recorded movements from connection between the giant bluefin -

117 Table 31. Releases and returns for giant (over 120 kg,) blucfin tuna tagged in last southward migration. Since less Newfoundland waters, by year of release, months at large, and area· of recapture. than I percent of the returns from bluefin tagged in New England wa- Year Releases Returns by Months at Large Total ters have been from outside the west- 0-5.9 6-17.9 18-29.9 30-41.9 42-53.9 >54 ern North Atlantic, it is highly probable that this fmal migration was from 1962 6 0 0 0 0 0 0 0 the New England or Canadian feed- 1963 3 0 0 0 0 0 0 0 ing grounds. The main significance 1964 41 0 0 0 0 0 0 0 of this return is the establishment of 1965 49 0 0 0 0 0 0 0 a connection between the nursery area 1966 49 0 0 0 0 0 0 0 south of Cape Cod and the spawning grounds in the south. Moreover, it 0 0 0 0 0 0 1967 6 0 most probably also represents the sea- 1968 217 1L 0 0 IL 0 0 2L sonal migration of large bluefin from 1969 195 0 0 0 0 0 IN IN the northwestern Atlantic feeding 1970 96 IL 0 0 0 IM,IN 0 3LMN area to their· spawning areas. This is the third important link 1971 94 0 0 1M 0 0 0 1M between the spawning area in the Gulf 1972 112 0 1G 0 0 0 IG of Mexico and the summer feeding 1973 4 0 0 0 0 0 grounds off the northeastern United 1974 14 0 0 0 0 States, As noted previously in this section, a large bluefin made a "di- 1975 0 0 0 0 rect" migration from waters north of 1976 0 0 0 Cape Cod into the Gulf of Mexico, Unknown 1 1L where it was recaptured during the • Areas: L = Local, M = MassallUsetts, N = Nova Scotia, G = Grand Banks spawning season. Another fish made an "indirect" migration, which might well have originated in the Gulf of Mexico, from the Straits of Florida, where post-spawning bluefin are prevalent, to New England waters. which feed in New England and Ca- age 11, or slightly less when recap- Thus tag returns have produced nadian waters in summer and early tured. Although this fish was in the considerable information on move- fall and those which spawn in the small size group when tagged, it must ments of large bluefin within the Gulf of Mexico in spring (Section have been a giant when it made its western North Atlantic, and from it VD3). As noted previously in this section, an "indirect" northward migration from the Straits of Florida to Massachusetts coastal waters has also 50· .••.. been recorded. "\ Another important tag return, \ \ I which was not from the above re- - lease groups, connects the feeding ,\ 'l__YIII'72--m'73 , '« y area off New England and Canada ",",' 'x.... ,. ~ 69--E ?J /' ~ with the spawning area for giants in .,;;.;' " '. '\'-••..~ 69--E? ~ •••../ / I the Gulf of Mexico. This fish, which '. :;:/ - -1im"771:Y7~- _-: .::::; .....,/ I .~:.:~;..~:.:\.~."::.:m'7'O-D. '74 •••••.••..- ./ • was tagged when it was in the small size group, was released August 4, 40' :~'::":':::;:) E!:'69--=7'79

1966, 38 nautical miles (70 Ian) south .:.:~~:: ',,! LEGEND by west of Martha's Vineyard, Mas- .: . o RELEASE LOCALITY sachusetts, and was recaptured April • RECAPTURE LOCALITY . : ",·Jr" - LESS THAN 40 1I0NTHS AT LIBERTY ",.;;:::.\ 18, 1976, in the north central Gulf of --- MORE THAN~OMONTHS AT LIBERTY ,"::.:;;: RELEASE DATE RECAPTURE DATE Mexico, 135 nautical miles (250 km) ~.:.:. E'64 -- JlIIt '65 south by east of the Mississippi River NOrc: LINES JOINING HeLEASES ANDHETUI1NS entrance (Figure 79). Its length when AHE DIAGHAMMATIC AND AHE NOT INTENDED released was about 56 cm and after 30' TO HEPHESENT MIGHATION HOUTES. nearly 10 years at liberty, the longest 80' 40· such period of which we have knowledge for a tagged Atlantic bluefin tuna, it was reported as 218 cm. Thus Figure 77. Geographic distribution of bluefin tag release and recapture data from the fish was age 1+ when tagged, and Newfoundland tagging studies.

Il8 75 70 65 80 50 45 longline catches and the observed re- ) ( \ lationships of the bluefm's distribu- ,r' tion and migratory habits to the ocean '...;'} currents in completing a hypotheti- "."' -,, cal model for the migrations of large ,---••.. _, western Atlantic bluefin. " ' .•..•.\ I The limits of the western Atlan- GRAND / tic area in which large bluefin spawn BANKS " ( have not been established, but the 411 I ••• I spawning grounds may include most '•••...... _./ of the deep (over 200 m) waters between latitudes 18°N and 33°N, and longitude 17°W and the coast (see 40 Section VD3). The only thoroughly documented LEGENO migration of large bluefm within this

o RHUS! ~ALlTY supposed spawning area is their • AEC,t,PTUAI; LOCALITY - U" 'HAN 10MON'"' AT LIBERTY - - MOR[ THAN 10 MONTHS AT L1I1£ATY' northward passage through the Straits CIRClED NUMKRI MPAIHNT IHDtVIDUAL O 'IIH nn •••!O 10 ", 1••• r: of Florida in May and June. This /tOTE: I.INn JDIIIIN5 IIELfASES 14110IIETIJ/INS AIf£ DIAfJIIAl/IIA'TIC AND AilE NfJr INTCND,/J movement may be traced visually TO IICPR£$E/ir 1111;/;""011 II't1UTO from boats or aircraft for about 65 nautical miles (120 km) along the northwestern edge of the Great Figure 78. Geographicdistributionofbluefm tag release and recapturedata from Bahama Bank from Orange Cay to Great Isaac (Figure 29) when condi- Nova Scotian tagging studies. tions are favorable (Farrington 1939, personal observations from u.S. Coast Guard Aircraft by 1. R. Rivas, into the eastern North Atlantic and Florida and summernursery and feed- H. A. Schuck and F. J. Mather in the South Atlantic. Although con- ing areas off northwestern North May-June 195I, Rivas 1955, Mather nections have been established be- America, a complete migratory pat- 1964b). A continuation of this mi- tween spring spawning areas in the tern has not emerged. We shall use gration along the 40 nautical mile Gulf of Mexico and the Straits of the temporal and areal distribution of (74 km) western edge of the Little Bahama Bank has also been observed (personal observations by the senior author at Memory Rock and Table 32. Releases and returns for giant (>122 kg) bluefin tuna, Thunnus Matanilla Shoal, June 1966, catches Ihynnus, tagged in New England coastal waters by years of release and time at off West End, Grand Bahama, per- large. sonal communications). The senior author also sighted and baited schools Year Releases Returns by Month at Large Total % of giant bluefin which were traveling 0-5.9 6 - 17.9 18 - 29.9 30 - 41.9 northward on the surface at the western end of the Northwest Providence 1966 2 0 0 0 0 0 Channel, between the Great and Little 1967 0 0 0 0 0 Bahama Banks, in May-June 1968. This unusual observation was a good 1968 6 0 0 1 0 1 16.7 indication of the continuity of this 1969 I 0 0 0 0 0 migratory route. 1970 4 0 0 0 0 0 Other migrations within the 1971 10 0 0 I 0 I 10.0 spawning areas may be deduced from the times and locations of catches, 1972 17 I I 0 2 4 23.5 sightings and/or the destruction of 1973 15a 5 I I 0 7 46.6 equipment of anglers fishing for 1974 9b 2 2 0 4 44.4 billfishes and other less powerful 1975 19 0 0 0 game, as well as occasional appear- 1976 34 0 0 ances of schools of bluefin. The Windward Passage appears "Includes6 releases of, and 4 1973 and I 1975 returns from fish tagged while to be a focal point in the migrations free swimming. of giant bluefin into the spawning bIncludes3 releases of, and 3 returns from, fish tagged while free swimming. area. Large fish, including some with

119 95· 85· 75° 45· fin through the Straits of Florida in 50· May and June seems obvious. It is LEGEND also indicated by occasional catches o RELEASE LOCALITY of deep swimming bluefin off Ha- • RECAPTURE LOCAL! TV 45· o RETURN NUMBER vana (Rivas 1955) and by the sightings of schools off Cay Sal, at . the southwestern corner of the Cay 40· Sal Bank (P. Pierce, T. Sanchez, personal communications). There are also strong indications 35· ~~'I:'~DA~E * D~fEAPT~~IE* that many bluefin follow the north t m'S6 (74-Btcml IIl'75 200kV 2 lIIl'74 1283IKjI Jr'7S 2S0ka,2~D"" 3 D'66 (53-59cm)IIl'?6 2'I8cm coast of Cuba westward from the 4 ]II'n miTT 26.3cm ~ _'78 JZ'n Windward Passage, through the Old 30° 6 ]II'T5 m'7S 280cm 7 :mI'71 m:'7e 340kQ,262cm Bahama and the Santaren Channels 8 D'n 3['78 365kV,27'cm 9 D'17 (273kO) n'19 "3ka.24~cm to the "tuna alley" in the Cat Cay 10 D'78 1204'.1 m'79 226'.,2S2cm U I5r'79 2~4kQ.2'6cm 25° area. We have received reports of sightings of schools moving through the Old Bahama Channel from per- 20· sons who operated aircraft there, but were unable to obtain precise details.

15° During cruise 62 of R/V Crawford in April-June 1961, which had been planned to study these migrations, additional evidence of such a migra- Figure 79. Geographic distribution ofbluefm tag release and recapture data from tion was obtained. Giant bluefin were northeastern North America tagging studics with recovery sites in thc Gulf of taken by longline in the Windward Mexico and Caribbean Sea Passage (sample 10, Table 25, Fig- ure 70), near Cay S. Domingo off the eastern end of the Old Bahama maturing ovaries (Table 25), have of large bluefin have been observed Channel, and at the edge of the Great been caught there by longline in April occasionally during this same season Bahama Bank on the eastern side of 1955, April 1960, and May 1951 in several consecutive years on the the Santaren Channel (sample 15, (Bullis and Mather 1956, Anonymous surface between Cozumel Island and Table 25, Figure 70) (Anonymous 1960, 1962). There are three major the Yucatan Peninsula. Many of these 1962, unpublished data). Sample 14 routes along which tuna might mi- fish have been hooked, but very few was taken about 60 nautical miles grate from the Windward Passage landed, by billfish anglers (personal (110 km) northwest of the western through the spawning areas and north- communications). Similar occur- end of the Old Bahama Channel and ward toward their summer feeding rences off the Mississippi River delta about 110 nautical miles (204km) grounds (Figure 31). have been reportcd (Nakamura and south by east of the center of the Cat The best documented of these Rivas 1972). The catch rate distribu- Cay sport fishery for giant tuna. The routes, although it is the longest, is tion charts of Wise and Davis (1973) capture of eight giant bluefin and the through the northwestern Caribbean, (Figure 32) and Le Gall (1974) indi- loss of many hooks, leaders and the Gulf of Mexico, and the Straits of cate that the winter conccntration branch lines, all at the inshore end of Florida. This pattern is indicated by around the Greater Antilles and in thc line, indicated a heavy concen- the distribution of 10ngline catches the southeastern Gulf of Mexico tration of the fish close to the steep of bluefin during cruise 30 of M/V moves westward and northward in drop-off at the edge of the bank at "Oregon" in the spring of 1955 (Bullis the spring, occupying the northern this station. Radio telephone reports and Mather 1956). Bluefin were taken Gulf as well as waters north of Cuba, from participants in a tuna tourna- in the Windward Passage, at stations Hispaniola and Puerto Rico. The ment at Cat Cay bewailed a prolonged south of the eastern end of Cuba and abundance of bluefin tuna larvae in dearth of fish. Two days later, they near the Cayman Islands and the Gulf of Mexico in April, May reported one of thc best catches in Cozumel Island in the northwestern and June also implies the prcsence of many years. The distribution of these corner of the Caribbean, but not one large numbers of adults (Richards four catches and the subsequent catch was taken at several stations in the 1976, Montolio and Juarez 1977). off Cat Cay strongly suggests that Caribbean east of the Windward Pas- The connection between the disap- contingents of bluefin migrate from sage. A migration between eastern pearance of this concentration of the Windward Passage through the Cuba and Jamaica was also indicated adults from the Gulf by the end of Old Bahama and Santaren Channels by the existence of a Cuban-based June (Shingu et ai. 1975) and the and continue northward through the spring longline fishery for giant blue- northward migration of large num- Straits of Florida. Because of the rup- fm in this area (Ubeda 1974). Schools bers (Tyler et ai. 1979) of giant blue- ture of diplomatic relations between

120 the United States and Cuba it was islands, this migrationmerges, at least early July (personal communica- impossible to verify this migration partially, with the one moving north- tions). We believe that the majority route completely by fishing in the ward from the Straits of Florida. The of these fish eventually enter the Gulf Old Bahama Channel itself. migration through Atlantic waters of Maine. Larger contingents prob- The third and most direct pos- east of the Bahamas has not been ably follow the easterly current far- sible route from the Windward Pas- observed visually, to our knowledge, ther and tend to enter the Gulf of sage to the northern feeding grounds and sightings oflarge bluefin between Maine more directly, presumably is through the Crooked Island Pas- the Bahamas and Cape Hatteras have through the Great South Channel in sage (Figure 31). Bluefin tuna are been extremely rare. In fact, the oc- many instances. Giant tuna usually abundant east and north of the Baha- currence of surface schools of giant arrive off northern Massachusetts in mas in spring (Shingu et al. 1975) bluefin travelling steadily in one di- June, and off southern Maine and and some of them probably spawn in rection off the northwestern Baha- southwestern Nova Scotia in July. these waters (Table 25, Figure 70). mas is a strictly local phenomenon They often arrive in the Halifax area, It also appears that these fish move which is unique in the western Atlan- however, in June. The latter may havt> northward in May and June (Shingu tic. It is quite similar to the periodic left the Gulf Stream at about the same et aI. 1975), as do those in the Straits runs of bluefin on which the traps at time as those which entered the Gulf of Florida. Several exploratory many localities in the Ibero-Moroc- of Maine, but followed a more direct longline sets were made in the can Bay and the Mediterranean de- course to this area. Large aggrega- Crooked Island Passage and west of pended, particularly the "return" run tions which have remained in the east- Great Inagua island from research of spent fish in July and August. erly current even longer may eventu- vessels of the Woods Hole Oceano- In addition to the lack of sight ally enter the Gulf of St. Lawrence graphic Institution in May and June records, no tag returns revealing the and Newfoundland waters in the lat- of 1958 and 1961 (Mather 1959, movements of giant tuna between the ter half of July. The times of arrival Anonymous 1969). No bluefin tuna Bahamas and Cape Hatteras have in American waters are from Section were caught on any of these sets, nor been obtained to date. Exploratory IVC2. In some years, considerable did we note any of the gear damage longline fishing results (Anonymous numbers of bluefin persist in fol- which these fish often cause when 1962, Zharov 1965) indicate that lowing the Stream much farther and they have been hooked and subse- these fish are much more available in eventually reach Norwegian waters quently escaped. This, of course, did waters east of the Gulf Stream than in August, September or October not prove that no bluefin follow this in those west of it, just as they are in (Figure 75). route, but, in our opinion, the fishing the northern Straits of Florida. Be- These transatlantic migrations results and other data indicate that cause of the tendency of bluefin tuna are discussed in the following Sec- they follow the other two routes in and other large pelagic fishes to travel tion C3. The local movements within much greater numbers. in favoring currents when migrating the feeding area between Cape Cod After the giant bluefin have for great distances (Sara 1973), we and Newfoundland have been de- spawned in these southern areas, they assume, in the absence of more pre- scribed previously in our discussion migrate northward to feeding grounds cise data, that many large bluefin of tagging results. off northeastern North America and, swim in the Gulf Stream northward The southward migration of large in some years, large contingents of to the vicinity of Cape Hatteras. Af- bluefin in late fall from their warm them go on to feeding areas off Nor- ter the Stream has passed the Cape season feeding areas to their south- way. and turned eastward, aggregations of ern wintering areas (Figure 14) The evidence for these migra- fish leave it successively, according around the Greater Antilles and off tions has been discussed in preced- to our hypothesis. We speculate fur- Brazil is one whose details are un- ing paragraphs. Daily records of ther that the distance that a given known. Most of the large bluefin catches at Cat Cay for numerous pre- group has travelled in the east-flow- leave their coastal feeding areas be- and post-World War II years (per- ing current may be an important fac- tween late September and early No- sonal communications) show that the tor in determining where it enters the vember (Section IVC2). As previ- passage through the Straits of Florida coastal waters. The first fish to leave ously stated, tag returns (Figure 79) occurs in strength, as indicated by the Stream after it passes Cape show a "direct" migration by a giant availability to surface fishing from Hatteras may approach the coast any- fish from the southwestern Gulf of early May to about June 20. where from off the Chesapeake Bay Maine in July 1974 to the western As noted previously, longline entrance to Cape Cod. This is indi- Gulf of Mexico in May 1975 and a catch records (Anonymous 1962, cated by a tag recovery off the Chesa- long term "indirect" migration from LeGan 1974, Shingu et al. 1975) in- peake Capes (Figure 76), catches in the nursery area for young bluefin dicate that a parallel but much more traps off northern (peninsular) Vir- off southern New England in August dispersed migration takes place in ginia, New Jersey, and Long Island, I966 to the north central Gulf of about the same period along the oce- and occasional sightings by fisher- Mexico in April 1976. These two anic edges of the Bahamas, and for men off southern New England of returns show movements from the considerable distances east and north giants travelling eastward, singly or feeding area to the spawning grounds, of them. After passing north of these in small schools, in late June and but do not tell us where the fish spent

]2] the winters. Two other returns, which nally westward over a rather broad Hispaniola. The other centers around may be more pertinent, were from front. The proposed migrations from the "bulge" (the easternmost part) of releases off the northwestern Baha- the wintering areas through the spring Brazil. It extends northeastward mas in May 1963 and June 1969 and spawning areas to the summer feed- nearly halfway to the nearest parts of recaptures off Recife, Brazil, in ing grounds generally follow the re- Africa, northward to latitude 15°N, March 1965 and off Buenos Aires, mainder of this gyre. Sella (1929 a, eastward to longitude 400W and Argentina, in February 1973, respec- 1929b) was most likely the first to southward, near the Brazilian coast, tively (Figure 75). These two migra- discuss the probable influence of the to latitude 100S. Tag returns (Figure tions were definitely to wintering Gulf Stream system on the distribu- 75) show that giant bluefin do, at grounds (in the northwest Atlantic tion of bluefin tuna in the Atlantic least occasionally, migrate from the frame of reference) and one even ex- Ocean. We consider the southward western North Atlantic into the South tends the probable wintering area far migration of large bluefin tuna as Atlantic. south of what was inferred from dis- one of the most challenging prob- The distributions of monthly tributional data. The information lems which remain to be solved. catch rates for individual years (Le available leads to the assumption that The wintering grounds of the Gall 1974) and of average monthly each of these fish had migrated south- large bluefin which feed in north- catch rates for groups of years ward from the northern feeding western Atlantic coastal waters in the (Shiohama et al. 1965, Shingu et al. grounds in the fall preceding the win- warm season have not yet been 1975) permit more detailed estimates ter in which it was recaptured. Since clearly defined. The giant tuna are of seasonal distributions and migra- they had been at liberty for periods less concentrated, and presumably tions. of 21 and 45 months respectively, less active, during the cold season Examination of the catch rates however, they might possibly have than in their spawning and feeding in the Antilles area on this basis led entered a different migratory pattern periods. They are dispersed over great us to believe that the winter distribu- of which we have no knowledge. In areas, and are almost always too far tion centered on these islands actu- any case, these returns do not pro- below the surface to be seen, or to be ally covered all of the Gulf of Mexico vide information as to the routes caught by surface gears. Moreover, and the Caribbean Sea, and the adja- which they followed in their final the opportunities for bluefin from dif- cent Atlantic waters up to latitude migrations. ferent spawning and feeding areas to 25 ON and eastward to longitude 600E. The recapture in December 1973 mix with each other may be at their Data for United States exploratory at the "tail" of the Grand Banks of a maximum during this period. Except and commercial fishing in this area giant which had been released in for a very few tag returns, the major (Wathne 1959, H. R. Bullis, Jr., per- northeastern Newfoundland coastal sources of information on the distri- sonal communications, personal ob- waters in August 1972 might indi- bution and migrations of giant blue- servations of the senior author) indicate a starting point for southward fin during the (northern) cold season cate that nearly all the bluefin taken migrations, but, since this fish had are the records of oceanic longline in these waters have been giants. been at large for about 16 months, fisheries. As already stated (Section The Japanese longline coverage this was an "indirect", or presumed, IVC3, and in this section), extensive in this area during the cold season movement from coastal waters. catch and effort data for the Japanese has been light. The data indicate, Japanese longline catch rates in longline fishery are available, but however, that bluefin were scarce November 1965 (Le Gall 1974) were there is little published information during most of the fall, but become relatively high (one to three fish per on the sizes of the fish which it cap- more abundant in December, Janu- 1,000 hooks) in a narrow area be- tures. This deficiency increases the ary and February. Coverage in March tween longitudes 59°W and 600W uncertainties inhercnt in deducing mi- was minimal, but bluefin were taken and extending from 44°N to 32°N. gratory patterns from these data. In in nearly half of the areas fished. In Although data on the sizes of the fish addition, the temporal and areal cov- April, catch rates rose drastically in have not been published, this area erage of the vast potential range of the Atlantic waters of the area, evi- might well represent the first part of the giant bluefin is incomplete, even dently because of the arrival of a southward migration of large blue- if the data from all years combined spawning fish. fin from Canadian coastal waters to are considered collectively for each Catch rates of more than one fish their wintering areas. month. per 1,000 hooks were rare until April. Consideration of the North At- The contours of relative abun- They occurred in only four instances, lantic circulatory system (Sverdrup dance, as indicated by longline catch each of which was in a different lo- et al. 1942) and the tendency of blue- rates (Figure 32), show two areas of cality. fin tuna to follow currents, however, maximum abundance in the first quar- Wathne (1959) reviewed United leads us to suggest that many of the ter of the year (January-March). One States exploratory and commercial giants may follow a hypothetical mi- of these is centered on the Greater longline fishing in the Gulf of Mexico gratory pattern following the North Antilles and includes the southeast- and adjacent waters. The commer- Atlantic gyre around the Sargasso ern Gulf of Mexico, the northwest- cial fishery was directed toward yel- Sea, first eastward, roughly along lati- em Caribbean and Atlantic ,,"aters lowfin tuna, T. alhacares. Wathne tude 40oN, then southward and fi- north of central and eastern Cuba and noted that giant bluefin occurred in

122 the northern Gulf in January and Feb- The available information indi- caught off eastern Brazil and along ruary. cates that the bluefin taken in this this proposed migration route, more-. The available evidence indicates area were giants. Zharov (1965), re- over, are inClose agreement with the that the distribution of bluefm in this porting on exploratory and commer- corresponding figures for fish taken wintering area is rather sparse and cial catches taken in the period from in the Straits of Florida in May and patchy. This estimate may be biased, February through June 1963, off the June, prior to the recent increases in however, since most of the longline South American coast from II oS to the sizes of giants taken there and fishing effort in the area was prob- lIoN latitude, stated that the bluefin elsewhere (Rivas 1955, 1976; Mather ably directed toward yellowfin tuna ranged from 205 to 254 cm in length, 1963a, 1974; Mather et a1. 1974a). rather than bluefin. with an average of 224 cm, and from Other contingents probably fol- The situation off the "bulge" of 151 to 283 kg in weight, with an low more northerly branches of the easternmost Brazil and in the narrow average of 183 kg. Thus all of them North Equatorial Current from mid- "waist" of the Atlantic between there were in our "large" category. Shingu Atlantic wintering areas, where their and western Africa was more com- et aI. (1975) also reported that the relative abundance is lower than off plex. Concentrations of bluefin oc- bluefin taken by longline in the equa- the "bulge", and join this migration curred off the "bulge" in each quar- torial Atlantic off northeastern Bra- ofT northeastern South America. or ter of the year (Figure 32). Examina- zil were of large size. the Antilles. Still others may migrate tion of the monthly charts suggests The April catch rate distributions directly westward, or even southwest- that two separate concentrations de- (Le Gall 1974) show that the area of ward, from more northerly oceanic veloped there, and then dispersed, high apparent abundance had ex- winter habitats to the spawning during each year. panded northeastward into the Gulf grounds. Bluefin were thinly distributed of Guinea, and northwestward almost While many giant bluefin evi- across the "waist" in July and Au- to southeastern Florida. The latter dently make lengthy migrations be- gust. In September a concentration extension of high catch rates, in our tween their wintering and spawning (bounded approximatelyby the Equa- opinion, represents a major migra- areas, others, which have wintered tor and latitude 15°N and by longi- tion of giant bluefin from the winter- farther north and west, east of the tudes 25°W and 40°W) formed in ing area described above to the Bahamas, or in the American Medi- this area. The maximum catch rates spawning grounds in the "American terranean may reach their spawning exceeded one fish per 1,000 hooks. Mediterranean" and in Atlantic wa- grounds with relatively little move- In October and November this con- ters east of the Bahamas and Florida ment. In the extensive areas where centration moved slowly southward, (Section VD3). This route would fol- the proposed wintering and spawn- uiltil its southern edge was at about low the major branch of the North ing areas overlap, the fish might re- 15°S latitude. In December, bluefin Equatorial Current off the northwest- produce wherever they happen to be were still present in the area, but the ern coast of South America (Sverdrup when the spawning period occurs. catch rates were all below one fish et aI. 1942) for much of the 3,500 The distributions of the higher per 1,000 hooks. This concentration nautical mile (6,575 km) distance. spring longline catch rates (LeGall probably did not consist of recent As stated previously, large bluefin 1974) suggest that most of the giant migrants from the North Atlantic. The tend to travel with favorable currents bluefin which migrated northwest- giant bluefin do not usually leave when they are migrating for long dis- ward along the South American coast their feeding grounds there until late tances. The change in the areas of subsequently followed the Antilles September or October (see Sections high catch rates from March to April Current in the Atlantic east of the IVC2 and IVC5) and this concentra- indicates that this migration might Antilles and the Bahamas, instead of tion had already developed in tropi- have been completed in about a the North Equatorial and Florida Cur- cal waters in September. month. This would have required an rents which flow through the Carib- The distribution of bluefin in the average speed of about 5 knots (9 km bean, the Yucatan Channel, the Gulf "waist" was generally thin in Janu- per hour), with considerable help of Mexico and the Straits of Florida ary, with more fish off the "bulge" from favorable currents. This rate of (Sverdrup et a1. 1942). than elsewhere. In February, how- migration is not inconsistent with As noted previously, these catch ever, the catch rates in the latter area those cited previously in this section data may have been biased by spotty increased, and a new concentration for migrations between other areas, fishing effort in the Caribbean and had definitely formed by March. This or for estimates of observed migra- the Gulf, and its possible direction extended approximately from 200S tory speeds. toward yellowfin, rather than blue- to 5°N latitude, and from 25°W lon- This hypothetical migration has fin, tuna. Even allowing for these gitude to the South American coast. not been verified by tag returns, since factors, the spring catches of bluefm Catch rates in this area were espe- no bluefin have been tagged in the in the eastern and southern Carib- cially high in the years 1962 through South Atlantic. As noted previously, bean have been very scarce. In re- 1965, sometimes exceeding 20 fish however, two fish tagged off the Ba- cent years, on the other hand, effort per 1,000 hooks. Since then, fishing hamas have been recaptured off east- directed toward bluefin in the north- in the area has been infrequent, and ern Brazil, or south of there. The ern Gulf of Mexico during the spawn- catch rates have generally been low. sizes given by Zharov (1965) for fish ing season has produced consider"

123 Table 33. Releases and returns by months at large for bluefm tuna tagged in the northwestern Atlantic, north of 35°00'N latitude and outside the 100 fathom (183 m) contour (offshorc tagging ceased in 1968).

Year Releases Returns by Months at Large 0-5.9 6-17.9 18-29.9 30-41.9 42-53.9 54-65.9 66-77.9 78-89.9 90.0-101.9

1957 5 0 0 0 0 0 0 0 0 0 1958 0 0 0 0 0 0 0 0 0 0 1959 97 I 0 0 0 0 0 0 0 0 1960 204 0 0 0 1 0 0 0 0 1 1961 2 0 0 0 0 0 0 0 0 0 1962 1 0 0 0 0 0 0 0 0 0 1963 42 4 1 0 0 0 0 0 0 0 1964 25 1 0 0 0 0 0 0 0 0 1965 37 0 0 0 0 0 0 0 0 0 1966 67 0 0 0 0 0 0 0 0 0 1967 8 0 0 0 0 0 0 0 0 0 1968 4 0 0 0 0 0 0 0 0 0

able catches (Shingu et a1. 1975, it. In our opinion, however, this ex- were recovered during the normal Shingu and Hisada 1976). tremely long circuit, extending from tuna fishing season, June through Oc- If "equatorial" bluefin did leave latitudes 400N to 500N to latitude tober. Six of the recaptures near the the Atlantic proper in significant lOoS, or even to 40oS, is the outer United States coast, each of which numbers during their northward mi- perimeter of a very broad pattern. took place after less than four months gration, there is a good chance that Although many fish may follow at large, represented "direct" migra- they did so through the Windward something resembling this route, oth- tions. Most of these, and a seventh Passage instead of through the chan- ers which winter farther north make which could be regarded as repeat- nels between the Lesser Antilles. Evi- correspondingly shorter circuits. ing its migratory pattern after 13 dence that giant bluefin migrated Some individuals may not even reach months at large, suggested that me- from that Passage to the Straits of the latitudes of the Bahamas. dium-sized blue fin approached the Florida by two routes - one through coast off Maryland and New Jersey c. Medium Fish the northwestern Caribbean, the in late June or early July from the Direct information provided by Yucatan Channel, and the Gulf of east, and then worked northeastward tag returns from medium sized (32- Mexico, and the other through the toward Cape Cod as the summer ad- 122 kg) bluefin tuna, and deductions Old Bahama and Santaren Channels vanced. The seasonal progression of based on their occurrences in the (Figure 14) has been presented pre- the recoveries in coastal waters re- coastal and oceanic fisheries (Mather viously in this section. We have found sembled that for the larger of the 1964b) enable us to offer a prelimi- no indications, however, of the route "small" bluefin tagged in those wa- nary hypothesis on their migrations by which the b1uefin reached the ters. They also coincided with the in the western North Atlantic. These Windward Passage. movements of the medium group fish are the only ones, among the It will be impossible to even es- through the coastal fisheries (Mather three major size groups, which have timate the percentage of the fish from I964b). The other two returns repre- been extensively tagged in this re- the equatorial Atlantic which com- sented much longer times at liberty, gion but never recaptured elsewhere. plete their northward migration in 31 and 93 months, respectively. The The most important tagging in- Atlantic waters, and the percentage former was released in November formation resulted from 491 releases which pass through the "American 1960 off the east end of Georges Bank Mediten-anean" or the adjacent chan- in offshore waters, from which nine and recaptured in June 1963 at Veatch returns have resulted (FAO 1972) nels and straits, until significant num- Canyon, south of Nantucket Island. (Table 33). Seven of the recaptures bers of bluefin have been tagged in The recapture location coincides equatorial waters. occurred on the continental shelf from closely with the possible inshore mi- off Maryland to just north of Cape The return to their spawning ar- gration route of the five fish tagged Cod, one near Yarmouth, Nova eas completes the prodigious migra- at 400N latitude, 68°W longitude in Scotia, and finally one at the edge of tory cycle of the giant "western At- thc same month and eventually re- the continental shelf south of Cape lantic" bluefin, as we now envisage captured in coastal waters (Figure Cod (Figure 80). All of these tags

124 71·

LEGEND R£U:A1I: 1..OCA&.Jn 0 A£CAP1URE Loc:AUTY • LESS TtIAIllO IIIOIntlS Ilr I.lIlElllTT - IIlOIlI THAN ~ MlltITHS AT UIEATY--- RELEAIE I»oTf:ClI MCAPT_ 1»oTl!ISI III ~ •••••••• fNUMlllt rIFFlIIH I~ lIDRI nwl CME ~'L..:s JDIIIIIIIIItILI!AII!6 AItII IfE7II/fW MIl ar.tMW..,nc A1IiI A/I£ ~ INrntIDI RJ nc~M~' ",.,..,. It«na

.. e • r'" ..f/

~...../

'l;".~!

Figure 80. Geographic distribution ofbluefm tag release and recapture data from North Atlantic tagging studies, illustrating offshore-inshore movements and one transatlantic. migration.

80). The last fish of this group was Movements during the summer St. Margaret's Bay (near Halifax). The tagged at Atlantis Canyon (south of feeding season in coastal waters, as years of abundance at Wedgeport Cape Cod) in November 1960 and indicated by the seasonal progres- generally coincided with those in recaptured off Cape St. Mary's (near sion of the returns from offshore re- Cape Cod Bay, as did the ages of the Yarmouth), Nova Scotia, in August leases and also by the movement of fish taken. The medium fish were 1968. In its nearly eight years of free- the fisheries, is from southwest to often abundant in Cape Cod Bay dom, its weight had increased from northeast. This general pattern could through most of August, but did not 69 kg (estimated) to 185 kg, bringing be observed from off Maryland to usually occur in number.s off it into the "giant" category. This re- the southern part of the coast of Wedgeport until September. These turn was the first to show a migration Maine. Medium fish have also been facts suggest a continuation of the from New England to Canadian wa- abundant in Nova Scotian waters in northeastward movement from Cape ters. some years, off Wedgeport (near Cod to Nova Scotia. However, fish Yarmouth) and, more regulady, in were usually numerous in Cape Cod

125 Table 34. Releasesand retwns for bluefmtooa 50 - 150cm (mostly50 - 100cm) taggedon the continentalshelfbetween Cape Hatteras, North Carolina and Cape Ann, Ma.'lSachusetts,Jooe - October.by year of release, months at liberty, and recapture area.*

Year Releases Area'" Returns by Months at Large

0-5.9 6-17.9 18-29.9 30-41.9 42-53.9 54-6549 66-77.9 ??? Total 0/0

1954 169 1 1 0 0 0 0 0 0 1 0.6 2 0 0 0 0 0 2 0 2 1.2 1955 215 0 0 0 0 0 0 0 0 0 1956 58 0 0 0 0 0 0 0 0 0 1957 34 0 0 1 0 0 0 0 1 2.9 1958 38 0 0 0 0 0 0 0 0 0 1959 25 0 0 0 0 0 0 0 0 0 1960 15 1 0 0 1 0 0 0 0 1 6.7 1961 150 1 0 2 3 2 0 0 0 7 4.7 1962 77 1 0 4 0 0 0 0 0 4 5.2 1963 29 I 7 2 0 0 0 0 0 9 31.0 1964 483 I 100 36 0 0 0 0 0 136 28.2 1965 1938 I 182 60 37 0 1 0 0 280 14.4 2 0 14 5 I 0 0 0 20 1.0 1966 3959 I 529 569 50 8 4 0 2 1163 29.4 2 0 12 3 0 I 0 0 16 0.4 1967 628 I 97 59 IS I3 0 0 0 184 29.3 2 0 I I 0 0 0 0 2 0.3 1968 260 I 88 19 8 0 0 0 0 liS 44.2 1969 341 1 12 85 12 2 I 0 0 112 32.8 1970 460 1 50 118 9 7 1 0 0 185 40.2 1971 622 1 38 99 16 1 0 0 154 24.8 1972 195 1 9 53 5 0 0 67 34.4 1973 511 1 59 23 8 I 91 17.8 1974 1733 1 73 127 50 250 14.4 1975 309 1 23 26 49 15.9 1976 2308 1 142 142 6.0 *Areas: 1 = Northwestern Atlantic, 2 = Bay of Biscay

Bay in October. This movement, if it and provides valuable data on the lowing pattern for medium fish did occur, represented a range exten- relative abundance of tuna in thc area emerges. Aller leaving the coastal sion, rather than a migration, of the by seasons (Wise and Davis 1973), waters in mid autumn, fish of this entire mass of fish. Since 1964 but size composition data for the size concentrate in great numbers in catches of medium-sized tuna in all catches are limited, and have usually the canyons along the edge of the waters north and east of Cape Cod been presented in such large tempo- continental shelf, from the Hudson have been small or negligible. ral and areal strata as to be of little Canyon off New Yark Harbor to the Information on the fall and win- value for this purpose. northeastern end of Georges Bank. ter migrations of the medium-sized Offshore exploratory longline In winter, few were encountered in bluefin is limited to deductions from catches of bluefin north of latitude these canyons, and the oceanic ex- results of exploratory oceanic fish- 35°N have consisted mainly of me- ploratory catch rates in this season ing (Mather and Bartlett 1962,Mather dium fish. and dense seasonal con- have been relatively low. The data 1964b, Wilson and Bartlett 1967). centrations have been encountered indicate, however, that the bluefin Commercial longline fishing in the (Squire and Mather 1963). Consider- tend to accumulate in loose aggrega- area has been much more extensive ing these data collectively, the fol- tions along the Gulf Stream front,

126 from east of Maryland and south of the last individual, which has been fishing for "school" tuna, which has Cape Cod, to south of the Grand described previously in this section, extended later into the fall than usual, Banks. In May and early June the was the first to connect the only off western Long Island and north- fish tend to concentrate in the west- known nursery area for juveniles in ern New Jersey (Moss 1967). ern part of this area, at least. The the western Atlantic with the major Until recently, little has been eastern part has not been sampled in spawning ground of giants in the Gulf known about the migration of small these months. The highest catch rates of Mexico. The returns from the Bay bluefin from their coastal nursery occurred in the area bounded by 38°N of Biscay will be discussed in Sec- ground, from which they disappear and 400N latitude and 68°W and tion VIC3. in late September or October, to their 700W longitude, where some fish The local recaptures included wintering area, which was presumed which appeared to be in advanced 1,408 in the fishing season in which to be in offshore waters. An interest- stages of maturity were taken (Sec- the fish were released. The 1,536 lo- ing description of their behavior prior tion VD3). In June, this distribution cal recaptures in subsequent seasons, to this movement, however, has been spreads westward to the edge of the after up to six years at large, indicate received from R. Hillhouse (personal continental shelf, and thence to the that many of these young bluefin visit communication), an experienced air coast, completing the migratory cycle this nursery and feeding area for two spotter of tuna in the area. He has of this size group. Since the explor- or more consecutive seasons, some- observed "hesitating" behavior atory fishing may not have covered times returning even after they en- (Lenier 1959) of small bluefin off all of the eastward part of the winter tered the medium group (ages 5-8). southern New England in late Sep- and spring distributions, the migra- Less has been learned about the tember and early October. Hillhouse tory pattern may extend farther to the migratory pattern of this size group reported sighting schools of small east in those seasons. than might have been expected from bluefin traveling together in a very the large number of returns, because large circle, which other schools d. Small Fish so many of them were from the re- joined successively until a substan- Over 14,600 small and medium lease area. Therefore deductions from tial aggregation of fish had been built bluefin have been tagged in coastal the movements of the fish through up. Then they all left the area to- waters between Cape Hatteras, North the coastal fishery, and from the lim- gether. This behavior is identical to Carolina, and Cape Cod, Mas- ited information available on longline that observed by Sara (1973) off the sachusetts, in the period July 1954 catches in oceanic waters will be used Strait of Messina. through October 1976, and 2,992 re- to supplement the tagging results in The six winter recoveries off the turns have resulted (Table 34) describing its migrations. edge of the continental shelf east and (Burnett et al. 1977, Mason and The 2,944 local returns showthat southeast of Georges Bank, near lati- Baglin 1977). Most of these fish were the young blucfin have generally tudes 40-41°N and longitudes 65- in the small group, 50-120 cm long, tended to migrate from southwest 66°W (Figure 81), have provided the but a few were mediums, 120-160 (Virginia, Maryland and New Jer- most significant progress in migra- cm long. The majority of the fish sey) to northeast (southern New En- tory studies of small northwestern were released from purse seine gland) within this nursery and feed- Atlantic bluefin in recent years. Two catches, a procedure which may ining area during the fishing season ofthese indicated"direct" migrations. cur very high tagging mortality (Mather et al. 1974b). This is also These fish had been tagged in the (Beckett 1974). The return rates from indicated by the movement of the coastal feeding grounds off the north- hook and line releases were consid- fishery (Mather 1974b, Sakagawa eastern United States in August 1973 erably higher than those from seine 1975). and July 1975, and recaptured in the releases in nearly all years (unpub- Migrations to waters north of above wintering area after five to six lished data at Woods Hole Oceano- Cape Cod (into Cape Cod and Mas- months at large, in January 1974 and graphic Institution). Lenarz et al. sachusetts Bays) have been recorded January 1976, respectively. Three of (1973), utilizing the results of the for only a few of the larger (when the other recaptures occurred inJanu- double tagging experiments which recaptured) individuals. As noted in ary after about 17 months at large, have been carried out in this area Section IVC2, however, small and and one in February after 30 months. since 1971, estimated the instanta- medium-sized bluefin tuna have not The extent of this wintering area is neous rate of tag shedding, on an been caught in numbers in the Gulf not known. Catches of bluefin taken annual basis, to be 0.31. of Maine for many years. during extensive exploratory fishing The returns included 2,944 from In the later part of some seasons from the research vessel "Delaware" the release area, seven from oceanic (September-October), considerable in the slope water between the Gulf waters in the western North Atlantic, numbers of small blue[in have re- Stream and the continental shelf dur- one from the Gulf of Mexico, and 40 verscdthe usual .migratory pattern, ing winter and early spring (Wilson from the Bay of Biscay. Since times moving from off southern New En- and Bartlett 1967) consisted mainly at large ranged up to six years, and gland into the approaches of New of medium fish (size data obtained even 10 years in one case, several of York Harbor. In some years, such as by Woods Hole Oceanographic In- these fish were in the medium size 1966, this "reverse" migration has stitution personnel on board the group when recaptured, and one was been followed by exceptionally good "Delaware" and from J. 1. Squire, definitely a giant. The migration of

127 young bluefin tUna. Since it appears 70 III 60 50 45 that few wcstern Atlantic fish in the small size group (ages 1-4) have attained sexual maturity, this pattern is not as greatly complicated by spawning activity as is that for small bluefin in the eastern Atlantic, which evidently spawn at younger ages (Sec- tion VHl).

45 The summer and winter habitats of the young bluefin, however, tend to expand with age of fish. Age 1 bluefin have very rarely been re- LEGEND o RELEASE LOCALITY corded in the Gulf of Maine, but age • RECAPTURE LOCALITY 2, 3 and 4 fish have occurred in Cape o RETURN NUMBER Cod Bay, at the southwestern end of ~~n:'~~*~* the Gulf, in great numbers in some ~ =:;: ::~::l~ ~ :18:: .,. years. Age 3 and 4 fish have been 3 ma:: '73 ItS kot I '74 II! ~J II" 4 :Ill '15 (lZOCIIl) 1 '78 _ t:;:; caught in Nova Scotia waters. In win- 5 111II'74 55<•• I '76(":,'·) • lDI1. '74 IOOCIIl I '76 ~ IDelft ter and spring, fish of ages 3 and, 1 llIl '73 72<10 II '76 40', especially, 4 have been captured * WEICHTS ARE FOIlt WHOLE FISH. FIGURES •• PARENTHESES W£A£ ESTIMATED much farther offshore than the wintering area mentioned above, but usually in small numbers. Figure 81. Geographic distribution of bluefin tag release and recapture data from middle Atlantic tagging studies, illustrating inshore-offshore movements. e. Very Small Fish Less is known about the migrations of age 0 bluefin in the western Atlantic, since no areas where they concentrate regularly have been Jr., W. F. Rathjen and P. C. Wilson, was approaching "giant" sizc, and personal communications). The pres- might have bcen entering the migra- found there. Hatching occurs exten- ence of small bluefin in the area tory pattern proposed for giants ear- sively in the Gulf of Mexico in May bounded by latitudes 40° and 45°N lier in this scction. and June. It also must spread widely over waters adjaccnt to the Greater and longitudes 45° and 700W has Tagging has produced no infor- Antilles and the Bahamas and far to been documented, however, by mation on the late spring migration the east and north of th~se islands. Shingu and Hisada (1976). About 90 of small bluefin from this wintering percent of their sample of Japanese area into the coastal feeding grounds. The limits of these areas in which longline catches in this quadrilateral In the first half of June 1959 bluefin are born have not been de- in January-February 1975, consisted however, an experimental longlin; fined, but we estimate that they may of small (less than 32 kg) fish, about fishing operation conducted from the extend over most of the deep (>200 half of which were in their third year fishing vessel "Golden Eaglc", in co- m) waters between latitudes 18°N and of life. operation with the Bureau of Com- 33°N and between longitude 6rw While in this wintering area, the mercial Fisheries (Wilson and Bartlett and the coast and islands. Another .small bluefm remain at subsurface 1967), obtained high catch rates (up probable hatching area is north of the levels (perhaps about 50-100 m). to 170 fish per 1,000 hooks) of small Gulf Stream and east of New Jersey Their growth almost ceases during (estimated sizes provided by J. L. and Maryland. Age 0 bluefin from this period (Section mC3), and their Squire, Jr., personal communication) all these areas must converge by vari- feeding and other activities are prob- bluefin tuna in the vicinity of latitude ous routes on the nursery grouhd~ ably minimal. 39° 20'N, longitude 68° 15'W. Since between Capc Hatteras and Cape Cod, The remaining offshore migra- the first appearanccs of small blucfin since that is the only western Atlan- tion was by an individual which was in coastal waters in rcccnt years have tic area in which age 1 bluefin are released about 40 nautical miles (75 occurred bctwecn thc Chcsapcake known to occur regularly en masse. km) south by east of Martha's Vine- Bay entrancc and Long Island The only route by which it seems yard in August I 966, and recaptured (Sakagawa 1975, personal obscrva- obvious that such a migration occurs off the southern end of the Grand tions of the authors), their approach is from the Gulf of Mexico and adja- Banks (about 42° 30'N, 71 ° OO'E) in to the coast may have been quite simi- cent waters through the Straits of August 1972. In six years at liberty, lar to that indicated by tag returns for Florida to the northern nursery area. its length had increased from 58 cm medium bluefin (Figure 80). The timing of this migration is un- (estimated age I), to 180 cm, with a The return to the nursery area certain. reported weight of 120 kg. This fish completes thc migratory cycle of the

128 The meager information avail- individuals from the Straits of Florida (numbers in parentheses indicate able (Rivas 1954, Mather 1963a, to Norwegian waters (Table 28). number of migrations, if greater than Mather et al. 1974) indicates that the Two transequatorial migrations one): 1961 (2), 1962, 1967. The other passage of these young of the year have been recorded for giant bluefin five could have occurred in the fol- through the Straits peaks in late July which were tagged off the northwest- lowing years 1960-1962(2) (migra- and August. Since no age 0 fish have ern Bahamas and recaptured off the tions in 1962 are considered improb- been tagged in these waters, this mi- South Atlantic coasts of South able because of the fat condition of gration is strictly hypothetical. It does, America (Table 28). the fish when they were recaptured), however, fit the known facts of ex- Biometric comparisons of blue- 1969-1976, 1972-1973, and 1973- tensive spawning in the Gulf of fm tuna from various parts of the 1974. Unfortunately, no body condi- Mexico and the tendency of age 1 Atlantic and the Mediterranean have tion data have been reported for the bluefin to concentrate almost exclu- been made and biochemical charac- tagged fish recaptured since 1962. sively in the Cape Hatteras-Cape Cod teristics of bluefin tuna from various Likewise; the weekly distributions of area in the summer. Age 0 bluefm do parts of the Atlantic have been com- body condition data for the landings occasionally appear in numbers, for pared. in northwestern Europe since then a few weeks at a time, between late In the following parts of this sec- are not available. The tag return data, July and early November in some tion we will present the data for these however, suggest another pulse of part of this northern nursery area, but migrations (Figure 75) and some re- west to east migrations in the period there has been no way to determine lated factors, and consider their im- 1972-1976. This may account for the where these fish had been spawned. plications. Finally we will discuss the somewhat increased availability of Thirty age 0 bluefin (42-48 cm identity of the stocks in the Atlantic giant tuna off Norway since their vir- long) were marked during an unusu- Ocean. tual disappearance in 1973. ally strong concentration of young of The fish which made the direct the year off Brielle, New Jersey, in b. Trans-Atlantic Migrations migrations, between May and early October 1973. Four of these have i. Giant Fish October, must have spent much of been recaptured off New Jersey, one Nine giant bluefin which had this time in deep oceanic waters in August 1974, and the others in been tagged off the Bahamas have where food is relatively scarce. Nor- June or July 1975 (Mather and Ma- been recaptured in Norwegian wa- mally, large bluefin tuna are concen~ son 1976). These returns proved that ters. Four of these recaptures repre- trated in the coastal areas in the more bluefin which visited the nursery area sented "direct" migrations since the northerly part of their ranges in sum- at age 0 were actually recruited to the fish had been at liberty for less than mer and early fall, where they are group of small (ages 1-4) fish which four months. The other five indicated feeding heavily (Sections IVC2 and supported the fisheries there in ensu- longer periods at liberty, which were IVC4). mg seasons. approximately as follows: 15.3 The two "direct" transatlantic mi- The first sustained and regular months for two fish, 26.5 months for grants which were examined after re- concentration of, these very small two, and 86.6 months for the remain- capture were very lean, in contrast to bluefin known to us begins in late ing one. Thus when the fish in the the fat condition typical of large blue- June or early July between Cape second group ("indirect" migrants) fin which have spent the summer in Hatteras and Cape Cod, when the had crossed the Atlantic, or whether coastal waters (Rivas 1955, Mather fish are almost exactly one year old. they had done so more than once, is 1962, Tiews 1964). Such lean blue- The important question of how they uncertain. The release (May 9-June fin, called "long-tailed bluefin" (1. reach that area remains to be an- 15) and recapture (August 4-0ctober Hamre, personal communication) by swered. 6) dates show that the "direct" mi- the local fishermen, had previously grants had crossed the Atlantic dur- been observed among lat.e season ing the warm season. One of these catches off Norway and in the North 3. TRANS-ATLANTIC AND made the trip of at least 4,200 nauti- Sea, but there had been no explana- TRANS-EQUATORIAL cal miles (7,800 km) in a maximum tion for their unusual body condi- MIGRATIONS, AND of 50 days, at a rate of 84 nautical tion. ATLANTIC STOCKS miles (I55 km) per day, or 3.5 knots Hamre (in Mather 1962) and (6.5 km per hr). Tiews (I 964) assumed that the lean a. Introduction These transatlantic migrations of condition of the recaptured fish re- Transatlantic migrations of blue- giant bluefin were not randomly dis- sulted from their having passed much fm tuna have been demonstrated by tributed over the years. Five of the of the summer in relatively barren tag returns showing migrations of 40 nine fish were released in the years oceanic waters, instead of the rich small (ages 1 and 2 when tagged) 1960-1962, two in the years 1972- coastal feeding grounds. They con- individuals between the New York 1973 and only two in the other 15 cluded that the "long-tailed bluefin" Bight (New Jersey to Cape Cod) and years in which bluefin tuna were were actually fish which had been the Bay of Biscay (Table 34, and tagged in the Bahamas. recruited from the western Atlantic migrations of 9 large (over 122 kg) Four of these migrations defi- during the years in which they were nitely occurred in the following years captured. Using extensive body con-

129 dition data from German North Sea (1964), are consistent with those in that several fish tagged and released catches of bluefm tuna, Tiews (1964) transatlantic migrations indicated by as small sized fish could have made estimated the percentage of the yearly tag returns, for those years in which the migration and been recaptured as late season (September IS-October both types of data are available. medium sized fish. 31) catches there which probably 5. Rodewald (1967) has shown were recruited from the western At- that the volume of west-east transat- iii. Smail fish lantic in the years 1952-1962. The lantic migration may have been in- Tag returns have demonstrated percentage recruited varied from 0.39 fluenced positively by anomalies in transatlantic migrations of 40 small of the 1953 catch to 0 in 1957 and the atmospheric circulation over the (less than 20 kg when tagged) blue- 1959. After 1954, the first year in North Atlantic which produce excep- fin tuna from west to east, and two which bluefin were tagged in the tionally strong west winds in the from east to west (Figure 75). Straits of Florida, the maximum esti- middle latitudes in certain years. His All of the west-east migrations mated recruitment of western Atlan- findings were generally consistent were from the New Jersey-Cape Cod tic fish to the northeastern Atlantic with the tag return data and Tiews' area to the Bay of Biscay (Mather occurred in 1960 (11 %) and I961 (1964) estimates of annual rc- 1960, 1969; Mather et al. 1967, FAO (33%) (Table 28). Two tagged fish cruitment. 1972). All of the releases took place migrated directly from the Bahamas 6. The two giant bluefin tuna in July and August, and the recap- to Norway in 1961. Two others, re- which were recaptured in Norwegian tures extended over the period from leased in 1960 and recaptured in waters in August and September June through October in subsequent 1962, were in the normal late-season 1962, 26-27 months after they had years. Therefore, these migrations fat condition when recaptured, indi- been tagged off Bahamas, were in evidently occurred mainly in the cold cating that they had probably crossed the nOlmal fat condition which is typi- seasons between the departure of the the Atlantic during a previous year cal of fish which have been feeding small bluefin from American coastal (1 960 or 1961), and spent their last heavily in coastal waters. Rodewald waters in late September or October, summer in the feeding grounds off (1967), moreover, found that atmo- and their arrival in the Bay of Biscay northern Europe. Thus the results of spheric conditions over the probable in late Mayor early June. The mini- the tagging, limited as they are, are migration route in July 1962 were mum distance travelled was about quite consistent with the estimates of distinctly unfavorable for movements 3,000 nautical miles (5,500 km) and recruitment based on body condition from west to east. lt is highly prob- the minimum time at large was 11 (Table 28). able that these fish had crossed the months. The average speed required To sum up, even though the ma- Atlantic in a previous year, and then would be only 0.4 knots (0.7 km/hr). jority of the returns from releases of entered into the migratory pattern fol- It is possible, however, that the times giant bluefin in the Straits of Florida lowed by large bluefin in the eastern at large were influenced by the eight have been from Norwegian waters, Atlantic. month period (October-May) in the following facts, or deductions, On the basis of this evidence, we which there was little or no fishing suggest that these returns do not rep- conclude tentatively that recruitment for small bluefin. resent a part of a normal annually of large bluefin to the northeastern The 40 west-east transatlantic repeated migratory pattern: Atlantic from the western Atlantic is migrations of small bluefin have not 1. The fish are in waters where variable, being important in some been randomly distributed over the food is scarce during the period when years and negligible in others. We years. Thirty-eight of them could giant bluefin are normally feeding speculate further that at least some of have occurred in a minimum of three heavily in rich coastal areas and re- these recruits remain in the eastern and a maximum of five cold season~ gaining the weight they have lost dur- Atlantic through the next annual feed- between 1965 and 1969. The other ing their spawning activity and the ing period, or longer. two could have taken place in a mini- related migrations. No east-west transatlantic migra- mum of one, and a maximum of two 2. The transatlantic migrations tions of large blue fin tuna have been periods between 1954 and 1959. have not been randomly distributed recorded. Although 554 large and me- Thus, over a 22 year period, all mi- over the years, but have occurred in dium-sized bluefin were tagged in grations of this nature revealed by clusters in certain periods. the eastern Atlantic off Norway and tag returns could have occurred in a 3. Tiews' (1964) estimates of an- Spain prior to 1968, none of the 51 minimum of four, and a maximum of nual recruitment of giant bluefin from recoveries has been west of longi- seven winter periods. All of the re- the western Atlantic in the late sea- tude 100W (FAO 1972). A rcnewed tm-ns were from only four of 22 yearly son North Sea fisheries, based on and sustained tagging program is re- release groups. Two of these groups, body condition data, also show that quired to determine whether such mi- however, 1,938 in 1965 and 3,959 in this recruitment is very irregular, with grations occur. 1966, were the largest. On the other peaks of high recruitment separated hand, the 169 releases in 1954 yielded by long periods of negligible recruit- ii. Medium Fish two transatlantic returns at a time ment. While there is no direct evidence when tuna tagging was a relatively 4. The variations in annual re- of medium sized fish making the mi- unknown practice, and larger num- cruitment, as estimated by Tiews gration from North America to Eu- bers of releases in 1955, 1964, and in rope, there remains the possibility 1968-1975 after tagging had been

130 well publicized, have produced no releases in the eastern Atlantic (34 years from earlier local taggings. The transatlantic returns at all. fish from 1967 through 1972) and of senior author attributed this situa- In companng the numbers of lo- returns from these (5 fish) (Aloncle tion to a probable influx of fish from cal and transatlantic returns, the 1,396 1973), however, are so small that this European waters, where very few local recaptures which occurred in comparison may not be statistically small bluefin had been marked. The the release season have been elimi- significant. Likewise, they give no subsequent recovery of two French nated. This leaves 1,517 local recap- basis for estimating the annual fre- tags verified this conjecture. This im- tures after eight months or more at quency with which east-west transat- migration may have been at least large, in comparison with the 40 in lantic migrations occur. partially responsible for the increase the Bay of Biscay. Transatlantic re- We lack the data required to esti- in the northwestern Atlantic purse turns have exceeded 1 percent of the mate the approximate total numbers seine catch of small bluefm from releases for only two years, 1954 and of fish which have made transatlantic 1,565 tons in 1969 to 4,200 tons in 1965. These figures indicate a much migrations from these tag returns. 1970. stronger tendency for young bluefin There are indications, however, that in the western Atlantic to return an- the volume of these migrations has c. Trans-Equatorial nually to their usual nursery ground, sometimes been sufficient to affect Migrations rather than to migrate across the At- the fisheries in the respective areas. The two South Atlantic recaptures of giant bluefin which had been lantic. Also, the data indicate that As noted above, the most impor- when such migrations do occur, they tant west-east transatlantic migrations tagged in the Straits of Florida (Fig- take the form of pulses, rather than a of young bluefm tuna were from the ure 75) have been discussed in the constant small flow. Finally, the fact release groups of 1954 and 1965. context of the migratory pattern pro: that the fish are in a given area in one Catch records for young bluefin in posed for the large bluefm which occur in the western North Atlantic summer and in such a distant one in the Bay of Biscay in this period are during the warm season (part 2b of the next does not support the concept somewhat confusing, but some data of an annually repeated cyclical mi- indicate considerable increases in the this section). As noted there, how~ ever, bluefm are widely distributed gration. landingsthere between 1954 and 1955 Deviations from established mi- and between 1965 and 1966. There in the tropical Atlantic during this gratory patterns may be caused by was also a great decrease in the west- same period. Among the possible ex- changes in environmental conditions. ern Atlantic purse seine catch in 1966. planations of this situation are the Rodewald (1967) showed that the Fourteen tag returns furnish fairly following: 1. Some large bluefin may transatlantic migrations of small blue- strong evidence for a significantwest- switch their summer feeding grounds fin recorded prior to 1967, like the east transatlantic migration between from the northwestern Atlantic corresponding ones of giant tuna, the 1965 and 1966 seasons. The case coastal waters to the frontal zones of might have been positively related to is less clear for the 1954 releases. the Equatorial Currents. Concentra- anomalies of the atmospheric circu- Since these fish had been at large for lation pattern over the North Atlantic five years, the actual date of their tions of tunas of various species have which caused unusually strong west- transatlantic migration is uncertain. been observed in the frontal zones of the Pacific Equatorial Current sys- erly winds in the middle latitudes. These fish were of age 2 (year class Two east to west transatlantic of 1952)when released, however, and tem (Blackburn 1965, Laurs and migrations of small bluefin tuna have nearly all subsequent small bluefin Lynn 1977, Murphy and Shomura been recorded (Aloncle 1973). These which have made similar migrations 1972). fish were tagged in or near the Bay of were recaptured in European waters 2. A separate stock oflarge blue- Biscay in September 1968 and Sep- before they had reached age 4. There- fin may exist in the tropical Atlantic. tember 1969. The former was recap- fore, it is most probable that these Neither of these explanations tured in August 1970 south of Cape two migrants had actually crossed the would be ruled out by the Cod, and the latter in July 1970 in the Atlantic between the 1954 and 1955 transequatorial tag returns, if fish of New York Bight (Figure 75). These seasons. On the basis of these returns, the hypothetical tropical stock re- migrations, in regard to dates and Hamre et al. (1966) suggested that produced in the western North At- localities of release and recapture, the great contribution of the 1952year lantic spawning area. These possi- constituted an almost exact reversal class to western European catches bilities will be discussed further in of the west to east transatlantic mi- might have been due to a major move- the conclusion of this section (Sec- grations just described. These results ment of fish of this year class from tion D). show that small bluefin sometimes the western to the eastern Atlantic. d. Stock Identification cross the Atlantic from east to west The only certain period of east- as well as from west to east. The west transatlanticmigrationwas 1969- i. Biometric Studies transatlantic returns constitute a much 1970. New England purse seine fish- Preliminary biometric compari- higher proportion of the total num- ermen informed us that tagged fish sons (Ginsburg 1953, Schuck and ber (40%) for the eastern Atlantic were scarce among the early catches Mather 1950, Mather 1959) of mor- taggings, than for those in the west- in 1970 in comparison with the nu- phometric and meristic data suggest ern Atlantic (0.4%). The numbers of merous returns obtained in previous that there are slight morphological differences between bluefin tuna of

131 the same sizes from the eastern and haustive studies are available at the the western Atlantic. These studies Woods Hole Oceanographic Institu- tcntatively concluded that the blue- indicated that the heads and the pec- tion and the Southeast Fisheries Sci- fin tuna of the two areas belonged to toral fins of individuals from the east- ence Center, National Marine Fish- a single breeding population rather ern Atlantic were slightly shorter than eries Service, Miami, Florida, and in than two geographically distinct those of individuals from the west- the literature: Heldt (1927) [Tuni- stocks. They noted that the evidence ern Atlantic, and that the maximum sia], Frade (1931) [portugal], Russell was not conclusive and that other depths of the former were slightly 1934a (North Sea], Navaz (1950a) hereditary characters might reveal a less than those of the latter, even lBay of Biscay], Nedelec (1954) degree of racial separation that was allowing for seasonal changes in this [North Sea], Buser-Lahaye and not apparent from a comparison based characteristic. Comparisons of mer- Doumenge (1954) and Doumenge on the Ox-I enzyme system. istic data, particularly gill raker and Lahaye ( 1953) [Mediterranean iii. Conclusions counts, by Robins (1957), Mather coast of France], Arico and Genovese In our opinion, neither the bio- (1959) and Tiews (1963) showed no (1953), and Genovese (1957, 1958) metric nor the biochemical studies significant differences between large [Tyrrhenian Sea], and Morovic have provided conclusive evidence samples of fish from the two areas. (1968) [Adriatic Sea]. European in regard to the identity of the stock, In a more recent study, Rivas workers have taken their measure- or stocks, of bluefin tuna in the At- (Rivas and Mather 1976), however, ments with tapes, following the con- lantic Ocean and adjacent seas. did not find significant differences in tour of the body (Anonymous 1932b), Furnestin and Dardignac (1962) have the characteristics noted above be- whereas United States workers have previously expressed this opinion in tween the samples from the two ar- taken "straight line" measurements regard to the biometric studies avail- eas. He did, however, show diver- with calipers (Marr and Schafer able at that date. Tiews (1963) did gences in the pectoral ray counts and 1949). Factors for converting not believe that the differences be- in the counts of gill rakers in juve- "straight" measurements of north- tween samples of bluefin tuna from niles 27 to 118 rom long. He also western Atlantic bluefin to the different areas which had been pro- found that the average length of the "curved" system are available at the posed by various authors would stand second dorsal fin was significantly Woods Hole Oceanographic Institu- up under critical inspection. The bio- greater for bluefin from the western tion. chemical studies now available are Atlantic than for those from the east- ii. Biochemical Studies admittedly of a preliminary nature ern Atlantic. Previous authors had Edmunds and Sammons (1971, and were based on samples which not noted this difference. Since Rivas 1973), after studying the genic poly- were not sufficiently numerous to and Mather have been in contact for morphism of tetrazolium oxidase in provide definitive results. many years, and have followed the bluefin tuna from thc western North It is our opinion that the identifi- same methods as closely as possible, Atlantic and from the Atlantic coast cation of stocks must be based largely these discrepancies show how diffi- of France using electrophoretic tech- on distributional studies and tagging cult it is to obtain consistent results niques, concluded that no differences results. Hypotheses in regard to the from biometric studies. The prelimi- could be found between the samples identity of stocks, as well as migra- nary results suggest, however, that from the two areas. On this basis, tory patterns, will be discussed in there may be distinct stocks of blue- and the indications of sporadic trans- Section VIlE, the concluding part of fin tuna on the two sides of the At- atlantic migrations from tagging, they this work. lantic. Extensive data for more ex-

132 VII. DISCUSSION, RECOMMENDATIONS, AND CONCLUSIONS

A. INTRODUCTION of the age composition of the Atlantic C. DISTRIBUTION, In this section we review and bluefin tuna stocks (Sakagawa and MIGRATIONS, AND present our conclusions on the aspects Coan 1973) would be required. Berry SPAWNING of the life history of the Atlantic blue- et al. (1977), however, questioned pre- fin tuna. Since the fisheries in each area vious age determinations for Atlantic 1. Introduction have heen described and their trends bluefm tuna. They concluded that me- Although there are differences in have been summarized in Section IV, dium size tuna (defined as fish weigh- details, the general patterns of distribu- we shall not refer to them further ex- ing between 56.7 and 136.1 kg) might tion, migrations and spawning on the cept as necessary to elucidate the life have been overaged by one or two years, two sides of the Atlantic fit the hypo- history of the species. Our opinions on and that giant fish might have been thetical migratory model presented in stock identity will conclude our discus- overaged by from one to 10years. They Section Vffi3, which may be summa- sion of the material in the preceding attributed this alleged overaging to the rized as follows: sections. counting of double or multiple mark- a Very Small Fish «50 em, Although much information on the ings on vertebrae or otoliths as repre- < 1 year old) biology of the Atlantic bluefin tuna has senting two or more years' growth Convergence from various spawn- been compiled in this work, we have rather than a single year's. ing areas to concentrate in nursery and not attempted to cover all of the aspects It is most important that the actual feeding areas. of its life history, nor have we been age composition of the "relict" popula- able to cite all of the works on the tion (as described by Caddy et al. 1976) b. Small Fish (50 em-l20 em, topics which we have discussed. We of giant Atlantic bluefm tuna be deter- 1 to 4 years old) shall point out the areas in which the mined with certainty. existing information seems to be defi- It is also important that the linear i. Immature Individuals cient, and make recommendations in growth rate of the larval, postlarval and Two-way migrations between regard to future research. early juvenile stages of blue fin tuna be warm season nursery and feeding areas determined for the various spawning and cold season wintering areas. areas. This information is needed in it Mature Individuals B. AGE AND GROWTH terms of length, rather than weight, to Three-way migrations between There has been good agreement permit better estimates of spawning warm season feeding areas, cold sea- on the sizes of Atlantic bluefin tuna at dates and localities from the collection son wintering areas, and late spring- ages I-II (Table I). There is less con- data for these very small bluefin tuna. early summer spawning areas. fidence in determinations for older ages. Seasonal variations in the growth Caddy et al. (1976) extended estimated rates of bluefin tuna up to 4 years old e. Medium Fish (120 em -185 age determinations to 25 years, and are reasonably well known (Mather and cm, 5 to about 8 years old) also provided separate von Bertalanffy Schuck 1960, Furnestin and Dardignac More extensive three-way migra- growth curves for males and females. 1962) but the data now available should tions between warm season feeding ar- These authors noted that earlier age permit extension of this knowledge to eas, cold season wintering areas, and determinations had ascribed fish smaller older ages. Information on this subject spring-early summer spawning areas. than 245 cm to age group 13, whereas could be greatly increased by more sys- d. Large Fish (> 185 em, > 8 tematic and extensive collections of size their own determinations indicated that years old) frequency data and biological material, 245 cm was roughly equivalent to ages Maximum three-way migrations especially from catches of the oceanic 14-15 for males and age 18 for fe- between warm season feeding areas, longline fisheries. males. cold season wintering areas, and spring- The possibility that the growth rate They also asserted that apparent early summer spawning areas. of the Atlantic bluefin tuna has in- underestimates of the ages offish more Except in certain situations related than 240 cm long had resulted in esti- creased as the size of the stock has to the reproductive cycle and/or the mates of L4, based primarily on data decreased should also be investigated. configuration of the coasts, the bluefm from fish less than 12 years old, which This possibility is suggested by the re- migrations are not confined to narrow were in excess of any sizes recently markable number of extremely large routes but spread over wide areas. The recorded for Atlantic bluefin tuna. If bluefin caught since 1970 (see Section species is very widely distributed, and their results should be validated, con- IV). capable of long and rapid movements siderable revisions of recent estimates

133 in response to various stimuli. Changes able, since the most important repro- been unusual occurrences, rather than in the currents, in the water tempera- duction of blue fin in the western Atlan- part of a regular migratory pattern, as ture, or in the availability of food may tic evidently occurs in the Gulf; and the noted in Section VIC. They will be affect its migratory behavior. Popula- only known warm concentration of discussed further in the context of stock tion pressure, either within the species yearlings in the region takes place in identification. itself or from competing species, may the Middle Atlantic Bight. also be an influencing factor. Even in There is a great need for extensive c. Medium Fish apparently stable conditions, the dis- tagging of age 0 bluefin when they The distribution pattern of the me- tributional behavior ofthe bluefin does appear in the Straits of Florida. Any dium (120 cm to 185 cm long, 5 to not confme it to strictly limited sea- same season recoveries from fish tagged about 7 years old) bluefm in the west- sonal habitats. These proposed migra- in this area would give a much more ern Atlantic differs mainly from that of tory patterns should, therefore, be re- definite indication of their distribution the small fish in its eastward extent. In garded as tendencies with which a ma- during the first year. This is one essen- recent years, their warm season distri- jor portion of the fish are apt to con- tial gap in our understanding of the bution and movements have been very similar to those of the small fish, ex- fonn in a general way, rather than fixed bluefin's life history. routes followed by entire size groups. tending from Cape Hatteras to Cape b. Small Fish Cod. Until 1966, they were often abun- 2. Western Atlantic Small bluefin (50 cm to 120 cm dant in the southwestern Gulf of Maine long, ages 1-4) concentrate in the nurs- from early August through October and a. Very Small Fish ery and feeding area between Cape sometimes into November and also During their first year oflife, blue- Hatteras and Cape Cod during the warm along the Nova Scotian coast from fm tuna (less than 50 cm long) in the season. They tend to move northeast- Yarmouth to Halifax. They usually ar- western North Atlantic migrate consid- ward along the coast as the season ad- rived in, and departed from, these north- erable distances from extensive and in- vances, and their range has extended ern waters later than the larger and completely defined spawning grounds into the southwestern Gulf of Maine in smaller fish which were present. Fish to the warm season nursery area for some years. The oldest fish in the group ofthis size, however, have very seldom small (50 cm-120 cm) bluefin in the tend to pass through this area first, fol- been taken north of Cape Cod in sig- Middle Atlantic Bight. They form their lowed by successively younger age nificant numbers since 1966. Their first regular and stable concentration groups. When the waters cool in Octo- maximum seasonal abundance south there in late June or early July when ber and November, they move offshore. of Cape Cod is rather unpredictable, they are approximately one year old. Their wintering area, as indicated by occurring early in the season in some The net movement during this first year recent tag returns, is in oceanic waters years and as a late season concentra- is basically one of concentration. The not far from the edge of the continental tion in others. routes are unknown, but they are prob- shelf off New England, Long Island These fish, like the small ones, ably varied and devious. and New Jersey. They occupy subsur- move offshore when the water cools in Their wide distribution in their first face waters in this period and grow the fall. Many of them concentrate in weeks of life has been established by much more slowly than during the the canyons along the edge of thee on- collections of larvae and small (less warm season. During late May and June tinental shelf in November, and then than 122mrn long) juveniles over much they tend to concentrate and move in- resume their offshore movement. Part of the Gulf of Mexico and off the coast shore to their summer habitat. A few of of their wintering area coincides with from southern Florida to New Jersey. these fish may attain their first maturity that of the small fish. It extends east- Their movements during the interven- near the end of their third year of life, ward between the edge of the continen- ing period are not known. Small and and many more near the end of their tal shelf and the Gulf Stream north of usually brief concentrations of new- fourth year. These fish probably spawn Cape Hatteras at least to the southern born fish occasionally occur inthe Cape in this same wintering area in late May tip of the Grand Banks. Cod-Cape Hatteras area between late or June. Thus a special spawning mi- Most, if not all, of the fish in this July and November. Tag returns have gration is not required and all of the group are mature, but their spawning shown that some of these fish, at least, fish in this group follow a two-phase area has not been defmed. Limited ex- return to the area when they are one or migratory pattern between their feed- plorations have located concentrations, two years old. Scattered occurrences ing and wintering areas, with the ranges including maturing fish, near the north- suggest distribution along the United of the fish increasing slightly with each ern edge of the Gulf Stream south of States coast from Cape Cod to the Mexi- additional year of age. The available southern New England and George's can border during the warm season, facts show that this is an east-west mi- Bank in late May and early June, but and from Cape Hatteras to southern gration, in contrast to the north-south this probably is only a partofthe spawn- Florida in the colder months. Thus these pattern which has been, and continues ing area. As in the case of the small fish may visit various areas during their to be, surmised. fish, spawning apparently does not re- first year of life. Occasional mid-sum- In a few years, tag returns have quire much deviation from the direct mer schooling in the Straits of Florida revealed migrations of small bluefin routes between the summering and suggests a migration from the Gulf of (one or two years old when released) wintering areas. The concentrations Mexico to the Cape Hatteras-Cape Cod from the Middle Atlantic Bight to the which form near the Gulf Stream in area. Such a migration seems reason- Bay of Biscay. These appear to have May and early June move inshore and

134 enter their feeding area in late June or abundance is usually highest off east- and its continuation, the North Atlantic July. In recent years, they have tended ernmost Brazil in late winter and early Current, until they reach the Norwe- to enter the coastal waters in the south- spring, and around the Anti~les. There gian coast in late summer or early fall. ern part of this area, off Virginia, MaI?'- are indications of an Important We believe that this is unusual behav- land, or southern New Jersey. Agam, northeastward migration along the ior rather than part of an annual pat- this is basically an east-west migratory South American coast from the former te~ for reasons enumerated in Section pattern, in contrast to the generally ac- area to the latter in April. This would VIe. These migrations will be discussed cepted concept of northerly and south- be a spawning migration, since the later in the context of stock identifica- erly movements. At least 500 medium prime known reproductive area in the tion. bluefm have been tagged in the northwestern Atlantic is in the Gulf of western Atlantic; all of the returns were Mexico. There is evidence that spawn- 3. Eastern Atlantic and consistent with the above pattern and ing also occurs in the enc~osed waters Mediterranean not one tag was returned from any other adjacent to the Gulf, and m the ocean a. Very Small Fish east of the Bahamas and the southeast- area. Very small (less than 50 cm long, . ern United States. These spawning less than I year old) bluefin are very d. Large Fish grounds are actually a part of the much widely distributed in the Mediterranean, The distribution and migratory pat- more extensive wintering area. Thus but are known from only a very small terns of the large (more than 185 cm, the giant bluefin may mo~e from t~eir part of the eastern Atlantic. Larvae and usually more than 7years old) bluefin wintering areas to their spawnmg very small (less than 10 cm long) juve- in the western Atlantic are much more ground by migrations of various lengths niles have been collected in many parts extensive than those of the smaller fish. and directions; some may not have to of the central and western Mediterra- The main warm season habitat of this move at all. nean and in the Black Sea. In amazing group includes much of the coast from The spawning season in the wes~- contrast not one has been captured in Cape Cod to the east coast of New- em Atlantic area extends from late Apnl the supposed reproductive areas in the foundland, including the southwestern through June, with the maximum emis- eastern Atlantic, despite prolonged and Gulf of S1. Lawrence, but usually ex- sion probably occurring in May and sometimes intensive efforts. The Ibero- cluding most of the Bay of Fundy. S~c- early June. When spawning is com- Moroccan Bay has long been regarded ondary concentrations, usually ofbnef pleted, the spent fish migrate no~- as the prime or only bluefin tuna spawn- duration, occur in the Cape Hatteras- ward toward their feeding grounds. This ing ground in the region on the s~ength Cape Cod area. In the 1930s, the late is most dramatically illustrated by the of the massive catches ofmatunng and 1940s and the 1950s, however, giant northward passage of spent bluefin spent fish which were formerly taken fish w'ere often quite abundant in parts through the Straits of Florida, close to by numerous traps along its coasts. of that area. The large fish usually ar- the northwestern Bahamas. The dura- Age 0 bluefin are observable ~. rive in their southern feeding grounds tion of this run, which usually occurs i.n great numbers over much of the Medi- between early June and early July, and strength from early M~y to mid J~ne, IS terranean, and are often available to in their northern ones in late July The consistent with the penod of maximum fisheries, from August through Novem- movements of fish within this large spawning stated above .. Soon. after it ber. Then they usually disappear, prob- area are not well known, except that leaves the Straits ofFlonda, thiS north- ably by simply remaining below th~ some fish released in S1. Margaret's ward migration is joined by a similar, surface during the coId season. In Apn I Bay, near Halifax in June or July have but less concentrated one which fol- they reappear, supposedly in or ne~ been recaptured in the Gulf of S1. lows the Antilles Current along the oce- the same localities, and finish out therr Lawrence in August or September. anic side of the West Indies and the first year of life without having moved The giant fish usually leave this Bahamas. The combined contingents extensively. feeding area in October and migrate to of giant fish tend to concentrate along These fish, along with older im- their very extensive wintering areas. the eastern edge of the Florida Current mature bluefin in the Mediterranean Routes of this migration can only be and follow it to beyond Cape Hatteras, are believed to be sedentary, remaining surmised. They probably spread over a where it becomes the Gulf Stream and near their birthplace until they attain very wide front, with some fish trav~l- gradually turns eastward. Contingen~s maturity. Their distribution, however, ling eastward and then southward With probably cross the Gulf Strea~ at van- is even more extensive than that of the the currents, while others follow more ous distances east of the Amencan coast known and supposed spawning areas. direct routes south. Since bluefin, most and resume their northward course. of which are large individuals, are dis- Reproduction is known or supposed to These groups of fish folio,,: vari~us occur off most of the western, northern tributed almost all over the Atlantic routes to different parts of their feedmg 0 and eastern coast of Sicily and in much between latitudes 35°N and 10 S dur- grounds. Their arrival ther~ completes of the south Tyrrhenian Sea; offwest- ing the northern cold season, the limits a prodigious circuit where distance m~y em Sardinia; around the Balearic Is- of this wintering area cannot be deter- vary for different groups of fish. ThiS lands; off western Libya, Tunisia and mined with certainty. There are indica- is, for most of the fish at least, a three Algeria; and in the Adriatic and Black tions, however, that it extends east- phase migration .. 0 Seas. The distribution of age 0 bluefin, ward to longitude 40 W and south- In some years, substantial contin- 0 however, extends into the Ligurian and ward in some cases, to latitude 40 S. gents offish remain in the Gulf Stream Thes~ fish are dispersed; the relative Aegean Seas, and the northeastern

135 Mediterranean. Dense concentrations em Atlantic somewhat resembles that Bay, or, possibly, off the Moroccan often occur in September and October off North America, but these fish, like coast before reaching the Bay. Most of in the waters just east of the Strait of the young of the year, are much more the spent fish probably proceed to the Gibraltar. No evidence ofspawning has widely distributed in the Mediterranean Bay of Biscay, completing the migra- been reported from any of these areas. than in the eastern Atlantic. tory cycle, but others may join the con- Therefore these fish must have moved The concentration of bluefin which centration off central Morocco. Pre- some distance from their birthplaces, became one year old in late spring or sumably, all of them return to the win- or there are several undiscovered re- early summer while in the Atlantic tering area there when the next cold productive areas. A migration from the coastal waters of Morocco generally season arrives. Black Sea might explain their occur- remains there, gradually working south- Movement patterns of the small rences in the Aegean and northeastern ward along the coast, until late summer bluefin are thus considerably more com- Mediterranean Seas. In any case, ifblue- or early fall. Then many of them mi- plex in the eastern than in the western fm do move about the Mediterranean grate northward, arriving off southwest- Atlantic. Separate summer nursery ar- during their frrst year of life, the net em Portugal in October or November. eas are available, one mainly for age 1 result of these movements is disper- Many of these fish spend the cold sea- fish and the other mainly for older fish. sion, in contrast to the strong tendency son there and then continue their north- In addition, more than one spawning to concentrate, which is typical in the ward migration in June, entering the area is apparently available to the ma- Atlantic. Bay of Biscay when they are about two ture fish. Thus a variety of migratory The situation in the eastern Atlan- years old. patterns may be followed, in contrast tic is, as noted previously, dramatically In some years, concentrations of to the simple "offshore-inshore" ar- different. Not only are the early stages age 1 fish occur in the Bay of Biscay rangement in the western Atlantic. Also, virtually unknown, but there is very but, again, no one knows whence these the small bluefin appear to follow a little information on the distribution of fish came. Bluefin of all the ages in- basically north-south migratory pattern the young of the year until October, cluded in the small size group, as well in the eastern Atlantic, whereas those when they are over 30 cm long. They as older fish, feed in the Bay of Biscay in its western waters move seasonally concentrate off Morocco in that month during the warm season. This is the in east-west directions. and in November and remain in the prime nursery and feeding areas for Small bluefm concentrate in more area, usually some distance away from small bluefin in the eastern Atlantic localities in the Mediterranean than in the coast, through the cold season. In and is analogous to the Middle Atlantic the Atlantic, and are more available June, when they are nearly a year old, Bight on the ocean's western side. The there to year-around fishing. they enter coastal waters, where most youngest fish, which are immature, usu- Most of the concentrations occur of them remain through the summer. ally remain there for the longest pe- in association with current systems, is- This appears to,be the only regular and riod. When three-year-olds and most lands, straits, or promontories. Some of important occurrence of age 0 bluefin of the four-year-olds are mature, their these which endure through all, or most, in the eastern Atlantic. Isolated occur- appearances inthe Bay are usually brief. of the year are at the Strait of Messina rences off the Canary and Salvage Is- Some spawning reportedly occurs in and Bonifacio (between Sardinia and lands and Cape St. Vincent have been the Bay, which may combine the func- Corsica) and the Bosporus, the Aeolian reported. No one knows from where tions of a feeding and a spawning Islands and the islands of Malta and the young of the year which concen- ground for some fish. A few bluefin are Kerkennah, and in the Adriatic Sea. trate off Morocco come. It is generally reportedly present in the Bay through- Seasonal concentrations occur in the assumed that they were hatched in the out the year, but the fishing season Gulf of Lions, the Gulf of Adalia, the eastern Atlantic, but we have stated our usually extends from early June through Alexandretta-Haifa-Cyprus triangle, the reasons (Section VIe) for believing that October. With the advent of the cold Ionian and Aegean Seas and the Sicil- many of them may have migrated from season, the small bluefin leave the Bay ian Channel. Most of these are avail- the Mediterranean. The tendency of and migrate southward to their winter- able during most of the warm season, bluefm to concentrate during the first ing area, which probably centers on the but diminish or disappear during the year of life appears to apply in the waters between Morocco and the Ca- spawning season in late spring and early eastern Atlantic, just as it does in the nary Islands. When the warm season summer and during the winter. Little is western side of the ocean, and in con- begins, they migrate northward. Dur- known about the migrations of tuna of trast to the dispersion which persists ing this movement, numerous fish are this size. They are believed to be rela- through this phase of life in the Medi- often trapped in a hydrological pocket tively sedentary until they attain matu- terranean. The eastern Atlantic con- off the central coast of Morocco and rity, usually at ages of three or four centration forms when the fish are only remain there through the season. The years. They then undertake migrations three or four months old, whereas in fish which avoid this entrapment may related to reproduction, but the extent the western Atlantic it does not occur folloW various courses. The immature of these is unknown. They may be con- until the fish are about a year old. fish probably proceed directly to the fined to the basins to which the fish are Bay of Biscay to feed. Some of the native, or they may range throughout b. Small Fish mature fish may accompany them and the Mediterranean. The spawning ar- The distribution of small fish (50 spawn and feed there. Other mature eas of the mature small fish are not well cm-120 cm long, ages 1-4) in the east- fish may spawn in the Ibero-Moroccan known. Probable areas include the

136 southeastern comer of the Tyrrhenian known, but probably small, percentage not known. Their concentrations tend Sea and the Ionian Sea off Sicily, the of these medium fish enter the Medi- to remain more or less stationary in a coast of Libya eastward to Bengasi, terranean with more numerous large given area for a few weeks and then and the Balearic Islands. The small fish fish and spawn there. These fish, and disappear. One of these absences oc- spawn considerably later than the larger most of those which have spawned in curs during the spawning season, which ones. Their reproductive season extends the Ibero-Moroccan Bay or adjacent probably extends from late June into through July and well into August; some Atlantic waters, then migrate to the feed- August. Spawning migrations begin even spawn in September. As with the ing grounds in the Bay ofBiscay. Some earlier, in Mayor June. The directions young of the year, the distribution of of them participate in the "return" run and distances of these migrations are the immature small fish is much greater with the large spent fish and others probably quite variable. Many medium than that of the known spawning area. migrate separately. StilI other fish may fish participate in the eastward "arrival" Again, this implies some migration by travel directly from the Wintering area run of maturing bluefin in May and these fish, unless the reproductive ar- to the Bay of Biscay and reproduce in June. This run is believed to include eas are much more extensive than is the secondary spawning area which ap- many large and some medium fish from now known. The tendency for small parently exists there. The medium fish the eastern Atlantic, but more medium bluefin to concentrate seasonally in one are usually most abundant in the Bay fish than large ones from the Mediter- or two relatively small areas, which is of Biscay from mid July to mid August ranean. The medium fish are usuaIly so pronounced on both sides of the or September. Their whereabouts there- most numerous in the later part of this Atlantic, is not evident in the Mediter- after is unknown until they presumably run, and favor the more easterly areas, ranean. return to their wintering area· in late such as the southeastern Tyrrhenian Sea fall. A secondary feeding area exists and the waters off eastern Tunisia and c. Medium Fish off the central coast of Morocco. Some Libya. The waters in these areas are While the bluefin in the eastern medium fish may go there, rather than somewhat warmer and more saline than Atlantic and the Mediterranean are in to the Bay of Biscay, after spawning in those in the more westerly areas fa- the medium size range (120 cm-I85 the Ibero-Moroccan Bay or the Medi- vored by the large fish. "Resident" me- cm long, from 5 to about 8 years old), terranean. Others possibly visitthis area dium fish also participate in the west- their ranges begin to overlap. This after leaving the Bay of Biscay. All of ward "return" run of spent fish in July greatly complicates the tracing of their these fish probably return to the same and August. Probably many of the old- life histories and adds correspondingly wintering area in late fall. Until 1962, est fish in this group accompany this to the uncertainties of existing knowl- large numbers of medium bluefm mi- migration into the Atlantic, shifting into edge about their life cycles. The dis- grated from their spawning ground to the wider ranging pattern ofthe "giant" tribution and migratory patterns of the feeding grounds also used by large blue- fish. This would occur when the fish medium fish in the eastern Atlantic are, fin off the southwestern coast of Nor- are about 185 cm long and about 9 or have been, more extensive than those way, passing west and north of the years old. Most of the younger "resi- of the smaIl fish. It is more difficult to British Isles en route. They usually ar- dent" fish probably remain in the Medi- assess these differences in the Mediter- rived there in mid or late July, and terranean. ranean. departed in late October. They rounded Virtually all of the medium fish in the British Isles again en route south to d. Large Fish this region are mature, but their spawn- their wintering area. Since 1962, few Under the hypothesis which we regard as the best explanation of the ing habits are not weIl known. They medium fish have been taken north of available facts, the large bluefin in the spawn later than the large individuals- the Bay of Biscay. Their coastal feed- probably through all of July in the east- ing thus became similar to that of the eastern Atlantic and the Mediterranean may be regarded essentially as a single ern Atlantic, and into August in the small fish. As noted previously, a com- aggregation offish. central Mediterranean. parable change in the summer distribu- In recent years, the migrations of tion of medium bluefin in the western The wintering area occupied by medium fish in the eastern Atlantic have Atlantic occurred in 1962. These range the majority of this group has not been been similar to those attributed to the reductions may have been related to defined. Probably most ofthe fish win- mature smaIl fish, with the exception the great decline in the apparent abun- ter in the Atlantic between latitudes 0 that some medium fish, at least, enter dance offish of this size group which 20 N and 35°N and the African coast the Mediterranean. Most of these fish occurred all over the Atlantic in this and longitude 30° W, but the total win- migrate from their wintering area off period, and has subsequently affected tering area may extend much farther, northwestern Africa (which probably the Mediterranean. especially to the south. extends from latitude 35°N to latitude The distribution of medium blue- Relatively small groups of large I5°N and from the coast to longitude fin in the Mediterranean Sea is quite bluefin winter in certain localities in 20° W) to the Ibero-Moroccan Bay or similar to that of the small fish. Both the Mediterranean-Black Sea system nearby waters, where the majority of groups often share the same habitats, where food is plentiful, particularly off them presumably spawn. Some of them, or adjacent ones. Medium fish are usu- the mouth of the Rhone and in the in numbers which vary from year to ally predominant, however, off the east Bosporus. There are two possible ex- year, migrate along the coasts of the coast of Spain. The medium fish pre- planations of these occurrences. The bay in the "arrival" run in which large sumably migrate farther than the small groups may comprise a resident Medi- fish are usuaIly predominant. An un- ones, but their migratory patterns are terranean stock (or stocks). On the other

137 hand, they may simply be contingents The positions where these repro- northern areas by a circuitous course of the main aggregation which have ductive migrations come near the coasts passing west and north of the British chanced upon satisfactory feeding are clearly indicated by the traditional Isles, rather than following the more grounds after spawning in the Mediter- locations of the traps. Those which direct route to these areas through the ranean, and stayed there rather than fished the arrival run in the Ibero-Mo- English Channel. Until 1962, most of returning to the Atlantic. At present, roccan Bay extended along the Iberian the larger giant bluefin moved north- there is no basis for determining which coast from Cabo de Santo Maria in ward along the Norwegian coast and explanation is correct. Portugal to the Strait of Gibraltar, and subsequently migrated southward into The main group of fish leaves the along the Moroccan coast from near the North Sea. Since then, however, Atlantic wintering area in late March Kenitra to the entrance of the Strait. nearly all of them have moved south- or April and migrates to the Ibero-Mo- The traps nearest Gibraltar took the ward along the Norwegian coast with rocean Bay forming the "arrival" run largest fish. In the Mediterranean, the the smaller members of this group, and (see Section VICldi for details) which traps off western and northern Sicily, the species has been scarce or absent moves along both shores of the Bay western Sardinia, and western Tunisia off northern Norway and in the North toward the Strait of Gibraltar in May have usuaIly taken larger fish than those Sea. These large bluefin usually enter and June. A fraction of these fish con- off eastern Sicily, Calabria, eastern Tu- Norwegian waters in July, spend the tinue to migrate eastward and spawn in nisia and Libya. The waters in the latter remainder of the warm season there, the Mediterranean. The others presum- areas are somewhat warmer and more moving southward along the coast and ably remain in the Ibero-Moroccan Bay saline than those in the latter and the 38 feeding voraciously, and depart from and spawn there. Further study is nec- 0/00 isohaline, which runs from the them in October. They again pass north essary to determine what percentage of Gulf of Sirte to Sicily, has been pro- and west of the British Isles and reach the "arrival" fish do remain and what posed as the eastward limit of the their wintering grounds east of north- percentage spawns in the Mediterra- spawning oflarge bluefin. Pelagic fish- ern Africa and the Ibero-Moroccan Bay nean. eries have recently indicated that large in November or December, complet- The major spawning grounds of bluefin are extensively distributed in ing their migratory cycle. the large fish in the Mediterranean are the western and central Mediterranean The south central Mediterranean probably off western and northern Sic- from late April into September, and appears to be the prime reproductive ily, western Sardinia and western Tuni- that spawning occurs extensively in off- area for the bluefin of the Mediterra- sia, where the waters are somewhat shore waters of the south Tyrrhenian nean. Its importance to the reproduc- cooler and less saline than those farther Sea. The fish of the "local" groups in tion of eastern Atlantic bluefin is more east, which are predominantly the the western and central Mediterranean, difficult to assess. This is one of the spawning areas of the smaller fish. presumably spawn with the more nu- most important questions in regard to Spawning is believed to occur between merous migrant aggregation, but this is the spawning, and the identification of mid-June and mid-July in the Ibero- conjectural. Larvae and/or smaIl (less stocks that remains unanswered. Moroccan Bay and central Mediterra- than 10 cm)juveniles have been found The lbero-Moroccan Bay has been nean. The numbers of fish which con- in many of these central and western generally regarded, at least in this cen- centrate off Gibraltar and the fraction areas. It seems very probable, how- tury, as the prime bluefm tuna spawn- of these which enter.the Mediterranean ever, that the large bluefin which feed ing ground in the eastern Atlantic, but depend considerably on the environ- and winter in the Sea of Marmara spawn not one bluefin larva, or smaIl (less mental conditions in and over the east- in the Black Sea, where collections of than 10 cm long) juvenile, has been ern Atlantic during the preceding weeks. bluefin larvae have been reported. Since collected in its waters. Research, in- The number offish entering the Medi- large maturing fish are said to be rare in cluding plankton collections, has been terranean depends greatly on the the Mediterranean east of the central carried on there almost continuaIly for strength of the inflowing Atlantic sur- Libyan coast and the eastern Ionian many decades by scientists of several face current, in which they travel. Sea, it seems improbable that the very nations, and the waters of the Bay, as After spawning, the fish in the large fish taken near Istanbul are mi- well as adjacent parts of the Atlantic Mediterranean initiate the westward re- grants from the Atlantic. The Bosporus and the Mediterranean, have twice been turn run, which occurs through July would be an ideal location for tagging surveyed very thoroughly during the and August. They follow the deeper and sonic tracking experiments. spawning season. The failure to collect Mediterranean current, skirting the east The "return" passage is completed any early stages of blue fin there cannot and south coasts of Sicily, and go out along the northern shores of the Ibero- be attributed to lack of effort. It has through the Strait of Gibraltar, contrib- Moroccan Bay in July and August and been suggested that the products of uting relatively small catches to the then the fish turn north toward the feed- spawning in the Ibero-Moroccan Bay traps on either side of the eastern en- ing grounds. Some of them follow the might have been passively transported trance. There they evidently join, or Iberian coast into the Bay of Biscay, into the Mediterranean by the inflow- follow, the fish which have remained where they usually remain for only a ing surface current before the early in the Ibero-Moroccan Bay in their month or six weeks. The majority, how- stages had attained full mobility. This westward migration along the southern ever, has usually proceeded to feeding seems unlikely, since the surveys men- coasts of Spain and Portugal, forming grourids off the coast of Norway and in tioned above covered all, or most of, the "return" run. the North Sea. They reached these the Alboran Sea (the westernmost part

138 of the Mediterranean) as well as the rocco throughout the year. There are maturing fish in May-June and the "re- Thero-Moroccan Bay, and also failed to no counterparts ofthese occurrences in turn" run of spent fish in July-August. coUect any early stages of blue fin there. the western Atlantic, since the species These runs include many giant fish and It seems inconceivable that bluefin do is rarely encountered in United States lesser numbers of medium ones from not spawn in the eastern Atlantic. On coastal waters south of Cape Hatteras. the eastern Atlantic. Maximum spawn- the other hand, the coUection ofbluefm The cold season occurrences of ing of large fish takes place from mid- larvae in so many parts of the Mediter- the blue fin are not as well known, but June to mid-July, but the reproduction ranean and the collection of "thousands" some differences between the patterns by medium fish is later and may extend (Sella 1929a) of juveniles less than 10 on the two sides of the Atlantic are into August. cm long in Sicilian waters offers a strik- evident. In the western Atlantic the Thus spawning occurs earlier in ing contrast. It is difficult to escape the small and medium fish winter sepa- the western Atlantic than in the east- conclusion that the Mediterranean is rately from the large ones, north of ern-Atlantic-Mediterranean system. most important to the reproduction of latitude 35°N, whereas in the eastern Also, the stock structure appears to be the bluefin tuna of the eastern Atlantic. Atlantic, the medium and small fish less complicated in the former area than share the northeastern part of the win- the latter. 4. Com pa rison tel' habitat of the large ones. The me- The occurrences of larvae and ju- The distribution and migratory pat- dium fish occur farther offshore than veniles less than 10 cm long are much terns of the bluefin on the two sides of the small ones in both areas and the better known in the western Atlantic, the Atlantic are quite analogous (Table large ones are distributed all the way where they are widely distributed, than 35). The extension of its range to much across the ocean from about 35°N lati- in the eastern, where their supposed higher latitudes off Europe than off tude to the equatorial region. There- range is relatively small. The larger age North America may be explained by fore, there is no clear cut separation o fish form a stable and regular con- the warmer temperatures in northern between the western and eastern groups, centration off Africa at least six months European waters. but the distributions of relative abun- earlier than any known occurrence of The similarity in the patterns is dance suggest that the former group is this nature off the American coasts. especially evident during the warm sea- more extensively distributed than the The routes which these fish follow from son when the distributions are best latter. their birthplaces to their earliest con- known. The Norwegian coast and the The spawning seasons and areas centrations in the respective areas are North Sea correspond to the Gulf of of the Atlantic bluefm, especially for not known. It seems probable, how- Maine and Canadian waters, being oc- the medium fish and the mature indi- ever, that analogous post-spawning cupied principally or entirely by large viduals of the small group, are far from migrations oflarge and new-born blue- and medium bluefin. The surface completely known. fm occur in the Straits of Florida and temperatures and salinities ofthese wa- The most important spawning the Strait of Gibraltar. After spawning ters, excepting the salinity in the North grounds which have been described are has taken place in the Gulf of Mexico Sea, are relatively low. South of these in the Gulf of Mexico (part of the on the one hand, and the Mediterra- areas, we find the principal summer American Mediterranean) and in the nean on the other, the large spent fish habitats of the small bluefin, the Bay of south central part of the European Medi- pass through the respective straits into Biscay and the Cape Hatteras-Cape Cod terranean Sea. These locations are the Atlantic. These migrations may be area. The surface temperatures and sa- analogous geographically, but the sur- followed, after a few weeks, by similar linities in these areas are somewhat face temperatures and salinities of the migrations of their offspring. higher than those farther north. The waters differ considerably. They are The migratory patterns joining northerly distribution of small bluefin about 23°C - 27°C and 36.0 0/00, re- these seasonal occurrences are likewise in the eastern Atlantic is lim~t~dby the ,"":llpectively, during the late April-early quite analogous, insofar as they have English Channel and the Bntlsh Isles,'" July spawning season in the Gulf of been determined. The longest migra- and the North Sea. Some large and Mexico, and 18.0°C - 22°C and 37.50/ tions are carried out by the largest fish. medium fish are taken in the Bay of 00 in the mid June-August spawning After feeding in the northern part Biscay, however. The summer habitat" season in the south central Mediterra- of their range, they make long south- of the small bluefm in the western At- nean. The stock structure is much sim- ward and generally offshore migrations lantic, on the other hand, is contiguous pier in the Gulf than in the Mediterra- to their vast winter habitats which ex- with that of the larger fish at Cape Cod. nean. The former area is occupied only tend, in the western Atlantic at least, In some years, great numbers of small by large bluefin during the winter and into the South Atlantic. The fish in the fish have entered the southwestern Gulf the spawning season, and by newborn North Sea and in Scandinavian waters of Maine. Large and medium tuna also fish from the time of their birth through pass north and east of the British Isles, occur frequently in the Cape Cod-Cape the fall and perhaps into the winter. instead of going directly south through Hatteras area, but usually.in moderate The spawning fish presumably come the English Channel. numbers and for short penods. from various parts of the western At- Shorter northward and more in- Small bluefin gather off the south- lantic. Bluefin of all sizes occur in the 'shore migrations in the spring bring west coast of Portugal from October Mediterranean throughoutthe year, but them to concentrations in spawning ar- through June, and very small or small large fish are relatively scarce there eas which are in the northern parts of ones are found off the coast of Mo- except between the "arrival" run of their wintering areas, or between their

139 Table 35. Patterns of spring and summer-early fall distribution of bluefin tuna on the two sides of the Atlantic.

Season Fish Size Eastern Atlantic Western Atlantic

Spring Small Morocco; Bay of Biscay Off edge ofCont. Shelf(N.E., U.S.) Medium lbero-Moroccan Bay, Medit.? Gulf Stream-Edge ofCont. Shelf Large Ibero-Moroccan Bay, Medit.? Bahamas-Gulf of Mexico

Early Summer Small Bay of Biscay; Morocco Middle Atlantic Bight Medium Ibero-Moroccan Bay, Medit.? Middle Atlantic Bight; Gulf of Maine Large Ibero-Moroccan Bay, Medit.? Cape Cod-Newfoundland Norway Mid-Summer-Early Fall Small Bay of Biscay; Morocco Middle Atlantic Bight Medium Scandinavia, Bay of Biscay Middle Atlantic Bight; GulfofMaine Large Scandinavia, North Sea Cape Cod-Newfoundland

Late Fall-Winter-Early Spring Small Morocco-Canary I. +? Medium Morocco-Canary I. +'1 N. edge Gulf Stream N of35°N Large N.E. AtI.-Canary I.-Morocco GulfofMex. W. Indies, Atlantic from 35°N to IO"S(or farther) and from

the American coasts to about 400W.

winter and summer habitats. Major de- much simpler in the western than in the They found no reason to believe partures from the ocean into relatively eastern Atlantic. The range of the fish that one or more separate stocks ex- land-locked spawning areas, and re- tends to increase somewhat with each isted in the South Atlantic. turns to the ocean, take place on both year of growth. As they noted, varying degrees of sides of the Atlantic. mixing, or none, might occur between The patterns may be compared to the components of dual- or multi-stock gyres which are greatly elongated in D. IDENTIFICATION OF combinations. Tag return data for blue- the north-south direction and distorted STOCKS fin tuna, however, indicated that mix- by the contours of the land masses and Much important information ob- ing tendencies may be strong. Th is was by detours into and out of the European tained recently supports the tentative especially true of the large fish. and American Mediterranean, where identifications of Atlantic-Mediterra- Mather et al. (I 974) concentrated important spawning occurs. They are nean bluefin tuna stocks by Mather et most of their discussion on two ques- also influenced by hydrological condi- al. (1974). These authors noted that an tions which still appear to be of para- tions and coincide with favorable cur- infinite number of combinations of mount importance: rents for much of their extent, particu- stocks, and degrees of mixing between I. The identification of the stock or larly in the western Atlantic. The south- them, might theoretically exist in the stocks of blue fin tuna in the Medi- ward migrations are probably more dif- Atlantic and connected seas, but con- terranean and the eastern Atlantic. fuse than the northward ones, and ex- sidered the following basic combina- 2. The identification of the stock or tend much farther into the middle of tions only: the ocean, affording considerable op- stocks of blue fin tuna in the Atlan- 1. A unit stock in the Atlantic and con- tic Ocean. portunities for mixing. The movements nected seas. in the eastern Atlantic gyre are gener- They briefly reviewed the histori- ally counterclockwise, while those in 2. One stock in the Atlantic system and cal opinions and developments in re- the western Atlantic gyre are generally another in the Mediterranean sys- search on the relationships between the clockwise. Thus, one pattern is roughly tem. Mediterranean and Atlantic bluefin a mirror image of the other. 3. One stock in the eastern At1antic and tuna. They then discussed Sara's (1964, The medium apd smaller fish on the Mediterranean, and another in 1973) hypothetical migratory model for both sides of the Atlantic move within the western Atlantic. the migrations of bluefin tuna in the these same patterns but to a much lesser Mediterranean, which has also been 4. One stock in the Mediterranean, a extent in the north-south direction. For described in the present work, and some second inthe eastern /\ tlantic and a both groups migration appears to be of the evidence supporting this theory. third in the western Atlantic.

140 They also noted the fmdings of Hamre turn" runs and the overall estimate of rather similar throughout the ocean. A et al. (1966, 1968, 1971) which showed the sizes of the fish taken (Shingu et al. correlation analysis, based on the dubi- that there were considerable differences, 1974) strongly support Sara's (1973) ous assumption that the sizes ofthe fish in both the trends of the catches and migratory theory. caught in the two fisheries were the their size composition, between the fish- The failure of the expedition "Mo- same, showed a positive correlation in eries for large bluefm in the eastern roc-Iberia I" to find early stages of the catch per unit of effort between the Atlantic and those in the Mediterra- bluefin in the Ibero-Moroccan Bay small fish fisheries in the northwestern nean. These authors conc1uded tenta- (Rodriguez-Roda 1975) and the dis- Atlantic and in the Bay of Biscay tively that the respective fisheries were covery of new spawning areas in the (Sakagawa and Coan 1974). supported by different stocks. Mather Mediterranean '(Duc1erc et al. 1973, Tag returns have traced several et al. (1974) noted, however, that the Scaccini et al. 1975, Piccinetti et al. transatlantic migrations of small and catches of many Mediterranean trap 1976) emphasize the probable depen- large bluefm tuna, as well as several fisheries had recently declined drasti- dence of the eastern Atlantic fisheries other migrations between widely sepa- cally, and the sizes ofthe fish taken had on recruitment from the Mediterranean. rated localities in the Atlantic. increased markedly. Thus, after a con- We therefore now attach even greater Studies of heart muscle protein siderable lag, they appeared to have importance to the spawning migration from bluefin tuna collected on opposite followed the trends of the northeastern of large and some medium (as indi- sides of the Atlantic showed no differ- Atlantic large fish fisheries. cated by tag returns in Rodriguez-Roda ences in the characteristics which were Mather et al. (1974) generally sup- 1969a) bluefin from the eastern Atlan- studied. The growth rates for bJuefin ported Sara's hypothesis, but also pos- tic into the Mediterranean, and the re- tuna in the Mediterranean, the eastern tulated a migration of newborn fish cruitment of newborn fish from the Atlantic, and the western Atlantic ap- from the western Mediterranean to the Mediterranean to the eastern Atlantic pear to be similar. Atlantic coast of Morocco in October fisheries. We conc1ude that the eastern The arguments for separate east- and November. They pointed out that Atlantic and Mediterranean bluefm con- ern and western Atlantic stocks were as this was the most plausible explanation stitute a stock which tends to separate follows: available for the continued productiv- into two components, one in each wa- Bluefin of all sizes are found on ity ofthe fisheries for small bluefm off t<::rmass, in its years of immaturity and both sides of the ocean, with the excep- the coast of Morocco and in the Bay of its earlier ones of maturity, and to spawn tion that very few larvae or small (less Biscay, and cited evidence that such a in the Mediterranean and spend the rest than 10 cm) juveniles have been found migration actually occurred. They also of the year in the Atlantic when the fish in the eastern Atlantic. recommended the tagging of very small exceed about 9 years in age and 100 kg Bluefm spawn on both sides of the bluefm in the western Mediterranean to 150 kg in weight. Atlantic (whetherthe bluefm which ar- and off the Atlantic coast of Morocco The status of the relatively small rive in the Ibero-Moroccan Gulf with in order to test this hypothesis and de- groups of large bluefin which occupy ripening gonads and depart with spent termine the sources of recruitment to the Mediterranean throughout the year gonads actually spawn in that area or in the major eastern Atlantic fishery for is unclear. Those in the western Medi- the Mediterranean seems irrelevant in small bluefin in the Bay of Biscay. The terranean could well be contingents of this context). There is no evidence of Mediterranean phase of this recommen- fish which have chanced upon a good extensive spawning in mid-Atlantic wa- dation has not been attempted, but a feeding area and dropped out of the ters. Spawning in the eastern Atlantic small-scale tagging operation was car- normal migratory pattern. The group (and/or the Mediterranean) is later than ried out most successfully off the At- of large bluefin which reproduces in spawning in the western Atlantic. lantic coast of Morocco in 1972 and the Black Sea and winters in the Sea of There is no correlation between 1973. This showed that at least some of Marmara is more likely, in our opin- trap catches in the eastern Atlantic and the recruitment to the Bay of Biscay ion, to be the nucleus of a separate Japanese longline catches in the west- fishery was indeed drawn from the Mo- population. ern Atlantic (Sakagawa and Coan roccan coast (Lamboeuf 1975). This Mather et al. (1974) noted that the 1974). important and relatively inexpensive situation with regard to bluefin tuna in The patterns of spring and sum- achievement further emphasizes the de- the Atlantic and connected seas other mer-early fall distribution of bluefm sirability of conducting similar experi- than the Mediterranean (North Sea, and tuna on the two sides of the Atlantic are ments in the western Mediterranean. the Baltic and its approaches, the Car- quite similar. Results which would be of great im- ibbean, and the Gulf of Mexico) was The principal exceptions were at- portance in identifying the bluefin also extremely complex. They stated tributed to different spawning habits. stocks in this critical area should be some arguments for a single stock oc- Spawning occurs later in the eastern obtained quickly and at modest cost. cupying the entire ocean, and others Atlantic (Ibero-Moroccan Bay and/or Important new information on the for two stocks, with spawning areas on Mediterranean) (about the end of June) question of the eastern Atlantic-Medi- the east and west sides ofthe Atlantic. than in the corresponding western At- terranean bluefin stocks has become The arguments for a single stock lantic spawning area (Bahamas, Gulf available recently. The progression of were as follows: of Mexico) (May, early June). The "re- Japanese longline catch rates in the area Fluctuations in catches, and trends turn" (spent fish) run in the Straits of and season of the "arrival" and "re- in their size composition, appear to be Florida occurs in May-June, whereas

141 the "return" run off southern Spain and captured in the western South Atlantic, of Mexico with the migratory passage Portugal occurs in July-August. This one off easternmost Brazil, and the other of similar fish through the Straits of accounts for the later arrival in north- off Argentina. No evidence that blue- Florida and their summer feeding oc- ern summering areas of the medium fin spawn in the South Atlantic has currence in New England and Cana~ and large bluefin in the eastern Atlan- come to our attention. dian waters. All of these migrations tic, as against the western Atlantic. Mather et al. (1974) concluded were recorded through taggings of gi- Also, the spawners in the Ibero- from the above information that the ant fish. An even more significant re- Moroccan Bay and in the Mediterra- evidence was insufficient to permit clear turn connected the Cape Hatteras-Cape nean, although predominantly large, in- cut conclusions, but believed that the Cod area, the only known nursery clude medium-sized and reportedly, most probable combinations were: ground for young bluefm in the west- even small fish, whereas all of those I. A single Atlantic or Atlantic- ern Atlantic with the region's most im- which spawn in the Bahamas-Gulf of Mediterranean stock and one or more portant known spawning ground in the Mexico area are giant fish (over 122 essentially Mediterranean stocks. Gulf of Mexico. Another important kg). 2. Two Atlantic spawning stocks, group of recent returns connected the Tag return data indicated that west one spawning in the western Atlantic Cape Hatteras-Cape Cod summer con- to east transatlantic migrations of small and the other spawning in the eastern centration of small fish with their pre- bluefin tuna are the exception rather Atlantic andlorthe Mediterranean, with viously unknown wintering area in oce- than the rule. As of the end of 1972, one or more essentially Mediterranean anic waters near the edge of the conti- about 9,700 small bluefinhad been stocks. nental shelf east of this summer habi- tagged in the Middle Atlantic Bight. They believed that the greatest tat. Previous returns had connected the Disregarding 1,112 local recaptures weight-of evidence appeared to favor nursery area south of Cape Cod with within less than six months of release, the second arrangement. They noted, the summer habitat of larger blue fin 1,201 returns were from the release however, that for management purposes north of this cape, and the offshore area as against 40 from the eastern At- it must be recognized that important winter and spring habitat of the me- lantic. interchanges between the two proposed dium blue fin with their warm season Recoveries from large bluefin tuna Atlantic stocks occur on an apparently feeding grounds north and south of tagged off the Bahamas were more nu- erratic and unpredictable basis. Cape Cod. These returns collectively merous in the eastern Atlantic (8) than They noted that the problem of the indicate a cohesive and self-sufficient in the western Atlantic (5), but, with stock structure of Atlantic bluefin is western Atlantic bluefin population. the collapse of the eastern Atlantic fish- one of enormous complexity. With the The most important remaining link to eries and increased effort in the west- existing depressed state of most of the be established among the occurrences ern North Atlantic, the trend in recov- fisheries, and the consequent diminu- of bluefin in the western North Atlantic eries has reversed itself. As with the tion or termination of research on the would be the migration of newborn transatlantic migrations of small blue- species in several nations, there was no bluefin from the Gulf of Mexico to the fm, those of large bluefm appear to be prospect that it could be solved defini- Cape Hatteras-Cape Cod area. It would important in some years and negligible tively in the foreseeable future. They be well worth the effort to tag some age in others. There have been no transat- concluded that management of the spe- o fish in the Gulf, or in the Straits of lantic returns from numerous taggings cies should be undertaken on the basis Florida. Other important but more dif- of large bluefin off New England, of the best information now available, ficult objectives of tagging western At- .Canada, Norway, and Spain. if its commercial extinction was to be lantic bluefin are to learn more about Preliminary comparisons of exten- avoided. the extent of their normal oceanic dis- sive data on the external morphology Conservation measures for Atlan- tributions, and to estimate the frequency of bluefm tuna from the eastern and tic bluefin were finally enacted by and importance of their transatlantic western Atlantic indicate that there are ICCATin 1975. Also, under the stimu- migrations. slight morphometric and meristic dif- lus of this organization, research on In regard to the latter, the infre- ferences between fish from the respec- bluefin tuna in several nations has ac- quency of west to east transatlantic mi- tive areas. tually increased. Unfortunately, how- grations of small bluefin has become There is little evidence for a sepa- ever, the failure of the fisheries in the increasingly apparent. The last tag re- rate stock of bluefm tuna in the South Federal Republic of Germany, Nor- turn revealing such a migration was Atlantic. The oceanic distribution of way and Portugal has forced some of from a fish tagged in 1967 and recap- the species appears to be continuous the most competent experts on the blue- tured in 1968. More than 4,400 small from off eastern Brazil to otTNew En- fin into other fields. bluefin have been marked in the west- gland and eastern Canada. Continued tagging in the western ern North Atlantic in the years 1968- Also, the more significant Japa- Atlantic by the Woods Hole Oceano- 1975. Not one of these tags has been nese longline catches of bluefin tuna graphic Institution has yielded results returned from the eastern Atlantic, al- appeared to progress seasonally from of great value in determining the mi- though 935 have been recovered in the offeastern Brazil in March and April to gratory patterns of the bluefin in that western part of the ocean in the years off Cape Hatteras by the end of June. area. Recent tag returns have finally 1969-1976. Transatlantic migrations of Furthermore, two bluefin tuna tagged and definitely connected the spawning small bluefin, at least in the west to east in the Straits of Florida have been re~ occurrence of giant bluefin in the Gulf direction, have become increasingly

142 nean and the Straits of Florida should Gibraltar, Messina, and Bosporus, tion to complete the picture of the life produce important results. Tagging of would be an efficient and positive way history of this species in the shortest giant tuna under present conditions is to obtain important infonnation. period of time. This will allow fishery difficult but is still producing good re- Present studies must be continued, scientists and managers to proceed with. sults. The use of sonic tags in key aras the data generated by them have the preservation and rebuilding, where eas, such as the Windward Passage and helped immensely in recent years. We necessary, of this valuable resource with the channels north of Cuba and around feel, however, that the above efforts the best understanding possible. the Cay Sal Banks and the Straits of will provide the most suitable infonna-

144 poor evidence for a single Atlantic Mediterranean is the prime reproduc- b) A more complex stock which stock. tive area for eastern Atlantic Mediter- might be subdivided into eastern At-' On the other hand, giant bluefin ranean bluefin. Thus the major spawn- Iantic and Mediterranean sub-stocks marked off the Bahamas continue to be ing grounds of the two proposed stocks until the fish are about 9 years old. The recaptured occasionally off Norway. are almost as far apart as they could be, eastern Atlantic substock probably re- Since 1969, however, more of these in an east-west direction, in the Atlan- cruits much of its strength from the fish have been recaptured in the west- tic-Mediterranean system. As noted pre- Mediterranean substock. The fish over ern Atlantic than in its eastern waters. viously, specific size composition data 9 years old constitute an eaStern Atlan- Unfortunately, no estimates of the re- on oceanic longline catches are mea- tic Mediterranean spawning stock. cruitment of western Atlantic tuna to ger. Shingu et al. (1974), however, pre- c) Possibly one or more localized .the northern European fisheries more sented some very useful data on the Mediterranean stocks. The most prob- recent than those of Tiews (1964) for sizes and abundance of blue fin usually able separate stock would be the one the 1954-1962 season have come to encountered in large areas of the Atlan- which feeds and winters in the Sea of our attention. These estimates were tic and Mediterranean. The area of mini- Marmarlil and spawns in the Black Sea. based on the body condition of the fish mum catches in the Atlantic north of landed during the late part of the sea- latitude 15°N is between longitudes son. 200W and 400W. The catches there E. RECOMMENDA nONS It is very puzzling that II of the 15 consist mainly oflarge fish. 111ismight It is clear that there are many un- returns from the I, 100 releases off the be the area where the proposed western answered questions relating to the stock Bahamas have been from outside the and eastern Atlantic stocks meet. The or stocks of bluefin tuna in the Atlan- western North Atlantic, whereas all of catches in the equatorial region between tic-Mediterranean system. As more data the 50 returns from 1,662 releases of latitudes 15°N and IODSconsist mainly become available, many of these ques- large bluefm in New England and Ca- oflarge fish, with a few mediums. South tions are beginning to be answered or nadian waters have been from within of latitude 100S, catches of Atlantic at least indications of one choice are the western North Atlantic. Further- bluefin are rare, and consist mainly of becoming clearer. There are some as- more, not one of more than 450 me- large fish. These data suggest that the pects of the bluefin's life history which dium bluefin tagged in offshore west- South Atlantic is a marginal area for we feel call for additional studies to ern Atlantic waters has been recaptured bluefin from the North Atlantic, rather more readily solve some ofthe gaps in elsewhere. This might be explained on than the habitat of a separate stock. The the data. Perhaps one of the most im- the basis that fish from the eastern At- groups of bluefin which remain in equa- portant in terms of stock structure is lantic spawned in the Gulf of Mexico. torial waters during the northern warm one we have mentioned, to determine The same arguments against the Baha- season have probably found good feed- what percentage of the "arrival" fish mas-Norway migration being a part of ing areas in the frontal areas of the which enter the Ibero-Moroccan Bay the regular migratory pattern of the currents, and remained in them instead spawn there and what percentage western Atlantic fish, however, could of migrating northward to coastal feed- spawns in the Mediterranean. Some be used against its being part of the ing areas. Concentrations of feeding type of a sonar scanning program might regular migratory pattern of the eastern tunas of other species in frontal areas be established in the Strait of Gibralter Atlantic fish. Also, not one ofthe large of the Pacific equatorial currents have along with a tagging program (sonic if and medium bluefm tagged off Nor- been reported (Blackburn 1965, Laurs possible) of some of the fish taken in way and Spain has been captured west and Lynn 1977, Murphy and Shomura the "arrival" run in the Bay. Environ- oflongitude lOoW. The most probable 1972). mental conditions must be examined to explanation of this phenomenon is that Sorting out the populations of determine what effect they have. the strong flow of the Gulf Stream sys- larger tuna in mid-ocean by conven- Knowledge ofthe distributive pat- tem, especially when the relatively slow tional tagging seems an almost hope- terns of the bluefin could be greatly North Atlantic Current is fortified by less task. Possibly some of the more increased by more comprehensive sam- exceptionally strong westerly winds, advanced biochemical methods will be pling of the sizes of the catches, par- and the tendency of the tuna to swim in more successful. ticularly in the oceanic longline fisher- favoring currents overrides all other We conclude from the material ies. More attention should also be given stimuli. Consequently, the fish do not considered that the following stocks to recording occurrences of age 0 blue- leave the current when they normally constitute the most probable arrange- fin. In the western Atlantic, at least, would to reach their American feeding ment: many fishermen apparently do not dis- grounds, and continue across the ocean. a) A western Atlantic spawning tinguish very small Thynnus thynnus Other recent indications of the stock which is generally self sufficient thynnus from other small tuna-like separation of stocks include the dis- and relatively uncomplicated. The chief fishes. Simple and clear identification covery of the major spawning grounds problems remaining are to define its keys should be distributed to individu- of giant bluefm in the Gulf of Mexico. wintering and spawning areas com- als who handle large numbers of fish, The failure to find early stages of blue- pletely. Contingents ofIarge fish from including dockmasters, fish handlers fin in the Ibero-Moroccan Bay and ad- this stock emigrate to the eastern At- and taxidermists, as well as fishermen. jacent Atlantic and Mediterranean wa- lantic fairly frequently. Contingents of Tagging of age 0 bluefin in key ters reinforces the view that the central small fish do so only rarely. areas, such as the western Mediterra-

143 VIII. BIBLIOGRAPHY

A. INTRODUCTORY NOTES Anonymous. 1932a. La pesea del touno Piscicoltura e di Idrobiologia, Roma 12(5):428. The following list of references in Tripolitania ne11931. Bollettino di contains many which have not been Pesea, di Piseieoltura e di Anonymous. 1950. Comite Atlantique; cited in the text. These may be of inter- ldrobiologia, Roma 8(1):87-91. Conference du thon. Malaga: 23-26 est to readers who wish to study the Anonymous. 1932b. Proces-verbal de la Mai 1949 - Tunis: 27-30 Juillet matters discussed in this work more conference d' e>..'Pertspour I' examen 1949. Rapports et Proces-verbanx closely or are interested in aspects of des methodes scientifiques et des Reunions, Conseil permanent the subject which have not been con- teclmiques a appliquer a I' etude des international pour I'Exploration de sideredhere. It is not, however, a com- poissons de la famille des Thonides. la Mer, Copenhague 127(2):appen- plete bibliogrnphy of the bluefm tuna. Tenue a Madrid et a Cadiz (sur dix,7-8. Additional references may be found In invitation du Gouvernement Anonymous. 1952. Les peches en FAO Fisheries Reports No.6, Vol. 4 Espagnol) du 16 au 22 Mai 1932 (avec Mediterranee. Proceedings and (1964), and in the standard biological trois annexes). Rapports et Proces- Technical Papers, General Fisheries and zoolo gica1 abstracts and records. verbaux des Reunions, Commission Council for the Mediterranean, Rome Much information on the species internationale pour I'Exploration 1:88-99. has been consolidated by some authors Scientifique de la Mer Mediterranee, Paris 7(n.s.):47-90. Anonymous. 1960. Libya. Tuna landings and organizations. Parona (1919), de up for 1959 season. Commercial Buen, F. (1925) and others have sum- Anonymous. 1933. Compte-rendu de la Fisheries Review, U.S. Fish and marized many of the pre-twentieth cen- conference d' experts pour I' examen Wildlife Service, Washington, D.C. tury WOlXs.In a series of reports, Heldt des methodes seientifiques et 22(1):75-76. reviewed most of the pertinent material teclmiques a appliquer a I' etude des Anonymous. 1962. Tuna migrations in which appeared in the years 1924-1937, poissons de la famille des lllOnides .the North Atlantic studied by RN as well as some of earlier dates, and (Madrid-Cadiz 16-22 Mai 1932). "Crawford". Commercial Fisheries provided extensive bibliographies. Rapports et Proces-verbaux des Review, U.S. Fish and Wildlife More recently, the Worlcing Groups on Reunions, Conseil penn anent Bluefin Thna of the Intemational COlm- international pour l'Exp] oration de la Service, Washington, D.C. 24(2):41- cil for the Exploration of the Sea have Mer, Copenllague 84(3): 91-103 42. been reporting annually on the trends (repeats text of Anonymous I932b Anonymous. 1963. Tuna stocks in North In bluefm tuna catches. Finally, a great without illu~1rations and annexes). Atlantic surveyed. Commercial deal of timely information is appearing Anonymous. 1934a. La pesca del tolUlO Fisheries Review, U.8. Fish and Wildlife Service, Washington, D.C. in the working documents, reports and in Tripolitania nella campagna del 25(8):36-40. publications of the International Com- 1933. Bollettino di Pesca, di mission for the Conservation of Atlan- Piseicoltura e di ldrobiologia, Roma Anonymous. 1966. Tuna and swordfish ticThnas. 10(2):272-276. distribution studies in northwest Atlantic continued. Commercial Anonymous. 1934b. Relazione sulla Fisheries Review, U.S. Fish and B. REFERENCES pesca del touno nelle Bcque delIa Wildlife Service, Washington, D.C. Tripolitania. Bollettino di Pesca, di Anonymous. 1928a. La pesca del touno 28(7):35-37. nel1927 in Tripolitania. Bollettino di Piscicoltura e di ldrobiologia, Roma Anonymous. 1968. Recommendations I, pesea, di Piscicoltura e di 10(6):797-802. VI, X and XI of the Tuna Meeting Idrobiologia, Roma 4(1 ):23-27. Anonymous. 1935a. La compagna del (palermo, May 1967) Appendix J, Anonymous. 1928b. La pesca del tOlmo touno in Tripolitania in 1934. Bollettino di Pesea, di PiscicoItura e di Recommendations. In General nel1927 in Cirenaica. Bollettino di Fisheries Council ofthe Mediterra- Idrobiologia, Roma II (I): 139. Pesea, di Piscicoltura e di nean, Report of the Ninth Session, Idrobiologia, Roma 4(1):28-29. Anonymous. 1935b. 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152 from the bluetin tuna working group. Scientitique de la Mer Mediterranee. J'Exploration Scientitique de la Mer On the development of the bluefin Paris 2(n.s.): 137-15 I. Mediterranee, Paris 6(n.s.): 175-288. tuna fisheries from 1950-64 and Heldt, H. 1927b Le thon rouge Thll111ms Heldt, H. 1931b. Le thon rouge et sa further obsenrations on size composi- thYll11US(L.) Mise a jour de nos pcche, elements d 'un nouveau rapport. tion of bluet in tuna catches. Conseil connaissances sur ce sqjet. Bulletin, Bulletin, Station Oceallographique de permanent internatioilal pour Station Oceanogmphique de Salammbo, Tunisia 21: 1-165 l'Exploration de la Mer. Copenhague. SalammbO, Tmlisia 7: 1-24 (duplicates (duplicates Heldt, H., 1931a). Statistical News Letters 26: 1-34. Heldt, H., 1927b). Heldt, H. I932a. Reperage des bancs de Hamre, 1.,Lozano, F., Rodriguez-Roda, Heldt, H. 1927c. Contribution a 1 etude thons par avion. Notes, Station J. and Tiews, K. 1968. 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Fourth report of Reunions, Commission internationale Proces-verbaux des Reunions, the bluetin tlma working group. pour l'Exploration Scientitique de la Commission internationale pour I Observations on the size composition Mer Mediterranee, Paris 3(n.s. ):93- 'Exp loration Scientitique de la Mer of blue fin tuna catches from 1967 to 114. Mcditerranee, Paris 7(n.s. ):203-318 1969. International Council for the Heldt, H. I928b. Le thon rouge (1'humlUs (duplicates Heldt, 1-1.,I932b). Exploration ofthe Sea, Copenhagen, thynllUS L.). Progres des recherches Cooperative Research Report Series Heldt, H. 1934. Le thon rouge et sa sur In question. Bulletin, Station A,23:1-1O. peche (8" Rapport) Annee 1932. Oceanographique de Salammbo, Rapports et Proces-verbaux des Hass, P. 1964.11 tonno dei Ponzesi. Tunisia 9:1-37 (duplicates Heldt, H., Reunions,.Commission Mondo Sommerso, Milano 6(11): 116. 1928a). intemationale pour I'Exploration Hayasi, S., Koto, T., Shingu, C., Kume, Heldt, 1-1.1929a. 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153 I.E.O. (Lab oratorios de Malaga, Palma y Juarez, M. I974a. i., Donde desova el Lamboellf. M. 1972. Tuna fisheries in Mar Menor.) and I.I.P. (Labordtorio de aum? Mar y Pesca, Habana 106:44-47. Morocco. Status at the beginning of Caste1l6n) 1976. Datos sobre IlL'; Juarez, M. I974b. Distribucion de las 1971. International Commission for pesquerias de tunidos y affines en el lonnas larvarias de algnnas especies the Conservation of Atlantic Tunas, Mediterraneo durante 1975. Interna- de la familia Scombridae en agua~ del Madrid, Report for biennial period, tional Commission for the ConselVa- Golfo de Mexico. Centro de 1970-71, Part III English version tion of Atlantic Tunas, Madrid, SCRS/ Investigaciones Pesqueras, Cuba 1-21 176-180. 76/53: 1-2 (mimco). (mimeo). LamboeuC M. 1975. Contribution ala International Commission for the Keyvanlar, A. 1962. SCrologie ct connais~Ulce des migrations des COllSeJVationof Atlantic Tunas. 1976. immunologie de deux especes de jeunes thons rouge a partir du Maroc. Data Record 8:339 p. thonides (Genno alalunga Groelin ct International Conunission for the Istituto Centrale di Statistica, Roma. Thunnus thynnus (Linne) de Conservation of Atlantic Tunas, 1949. Annuario Statistico Italiano, I'Atlantique et de la Mcditemmee. Madrid, Collective Volume of Edizione 1949,216. Revue des Travaux de I'[nstitut des Scientific Papers 4: 141-144. Istituto Centrale di Statistica,.Roma. Peches Maritimes, Paris 2(,(4):407- Laurs, M. and R. J. Lynn. 1977. Seasonal 1951. AlUmario Statistico Italiano, 456. migration of North Pacific Albacore, Edizione 1951,212. Kume, S. 1976. Japanese lisheries and Thunnus alalunga, into NOIth American coastal waters: distribution, Istituto Centrale di Statistica, Roma. research activities on tunas and tuna- like fishes in the Atlantic Ocean, relative abundance, and association 1954. Annuario Statistico Italiano, with transition zone waters. Fishery Edizione 1954, 171. 1973-1975. International COlrunission lor the COllSeJVationof Atlantic Bulletin 75(4):795-822. Istituto Centrale di Statistica, Roma. Tunas, Madrid, Report for biemual LebedefT, W. 1936. Paradise for big 1957. Annuario Statistico Italiano, period, 1974-75, Part II (1975) Game fishing tunny 700 k; swordfish Edizione 1957, 193. English. version 187-196. 180 kg; shark 1800 k. Winter season Istituto Centrale di Statistica, Roma. KUllle, S. 1977. Japauese tisheries and 1935~36 in Turkey. fishing Gazette, 1960. Annuario Statistico Italiano. rcsecu'ch activities on tunas and tuna- London 113(3102):420-421. Edizione 1960, 182. like lishes in the Atlantic Ocean, I,e Danois, E. 1938. L'lntluence des Istituto Centrale di Statistica, Roma. 1'>74-197(,.lutemational Commission transgressions sur la biologic etla 1963. Annuario Statistico Itali~U1o, fill' the Conselvat;on of Atlantic pcche; III L' Atlantique (Histoire et Edizione 1963,202. Tlmas, Madrid, Rcp0l1 1'01' biennial vie d'uuocean), Paris, Albin Michel Istituto Centrale di Statistica, Roma. period, 1976-77, Pcu1 1(1976) English 246-28(,. 1966. Annuario Statistico Italiano. version 194-204. Lee, J. Y. 1965. Observations surla Edizione 1966, 198. Laboratorio Oce~Ulogr{llicode Canarias. serologic et l'immunologie des thons Istituto Centrale di Statistica, Roma. Pesquerias de tunidos en ]as Islas rouges (Thunnus thynnus Linne) de 1969. Annuario Statistico Italiano, Canarias. International Commission Meditcrranee. Rapports et Proces- Edizione 1969, 174. lor the Conservation oI'Atlantic verbaux des Reunions, Commission Tunas, Madrid. Collective Volume of international pour l'Exploration Istituto Centrale di Statistica, Roma. Scientilic Papers 2:314-319. Scientifique de la MerMediterranee, 1972. Arumario Statistico Italiauo. Monaco 18(2):225-228. Edizione 1972,206. Laboratorio Oce~Ulognilico Palma.l.E.O. Caste1l6n, Laboratorio OCClUlOgrafico Lee, J.Y. 1968. Note complementaire sur Istituto Centrale di Statistica, Roma. Malaga. 1976. Primeros datas sobre la I'immunologie des thons rouges 1974. Annuario Statistico Italiano, pesqueria de t(midos y alines en d (7hunlllls thynnus Linne) de Edizione 1974,218. MeditelTaneo y sllratliintico espafioles. l' Atlan tique et de la Mediterranee. Iyigiingor, D. 1957. Methods and gear Intemational Conunission fill' the Rapports et Proces-verbaux des at present in use for tuna fishing in ConselVation of Atlantic Tunas. Rewllons, Commission international Turkey. Proceedings and Technical Madrid. Collective Volume or pour l'E)o,:plorationScientifique de la Papers, General Fisheries Council Scientilic Papers 5(2):261-266. Mer ML'diterranee. Monaco 19(2):279 for the Mediterrancan, Rome LaJami, J. 1971. Contribution (1l'elllde I,e GJIL 1. 1927. Contribution ~11'etude 4(33):251-255. systematique biologiqlle ecologiquc et de la biologie du thon rouge (Thunnus Jordan, D. S. and Evenmum. B. W. 192(,. statistiqul: des poissons de la pccherie thYnllII.I'L.). Sur la presence de thons A review of the giant mackerc\-like d·Alger. Pe\a!!os,Alger 3(4): 1-150. rouges eu Mer du Nord et dans fishes, tunnies, spearlishes, and Lalami, Y. TdlaL S., BmTois, J.M., l' Atlwltique nord-est. J011I11111du swordfishes. Occasional Papcrs ofthe Piccinetti, C. (Jnd Piccinctti Manrrin, Conseil, Copenhaglle 2(3):309-331. California Academy of Science, San G. 1973. Observations SUI' les oeurs Le Gdll, 1. 1929. Le thonrouge (Thunnus Francisco 12:1-113. ct larves des thonides des cOtes thynnus L.) en Mer du Nord et dans Juarez, M. 1972. Larvas del atUn de aleta algeriennes. Pelagos, Alger4(2):54- I'Atlcultique nord-est. Joul11aldu azul en e1Banco de Campeche. Mar y (,5. Conseil, Copenhaglle 4(2):200-206. Pesca, Bahana 86: 50-51.

154 Le Gall, J. 1950. Dims les parages de Atlantic TlUlas, Madrid, Report for Maldura, C. M. I'>65.Studio per il SaintJeande Luz, en 1949. biennial period, 1970-72, Part 1II regolmllento di esecuzione alIa legge Observateurs; Castagne et Fauvel. In English version 181-187. 14 Luglio 1965 N. 963 sulla disciplina Thunides: Thon rouge (Thunnus Linnaeus, C. 1758. SystemaNaturaeper delIa pesca marittima. Ministero delIa thynnus L.). Annales biologiques, regna tria natume secundum classes, Marina Mercantile, Direzione Conseil pennanent international pour ordines, genera, species cum Generale delIa Pesca Marittima, Roma I'Exploration de la Mer, Copenhague characteribus differentilis, synonymis, 1-45. 6:71. locis. Editio decimareformata, Tom. 1 Maldura, C. M. 1969. Disciplina della Le Gall, 1 1952. Lethonrouge (Thunnus (Regnum animale), Lithoprinted, pesca marittima (Legge e regolamento thynnus L.) dans Ie Golfe de Gascogne 1956, British Museum of Natural di esecuzione). Ministero della Marina en 1951. Observations de P. Creac'h. History 1-823. Mercantile, Direzione Generale delIa Mensurations de Castagne et Fauvel. Louys, E. 1953a. Florida. In Midsummer Pesca Marittima, Roma, In Thonides. Annales biologiques, peak at hand. Wide variety of sport Marr, J. C. and Schaefer, M. B. 1949. Conseil pennanent international pour and game species now available. SaIt Definitions of body dimensions used I'Exploration de la Mer, Copenhague WaterSportsmlUl, Boston ]4(23): 1-3. in describing tunas. Fishery Bulletin, 8:82-83. Louys, E. 1953b. Florida. In SpOli fish Fish and Wildlife Service, United LeGalI, J. 1954. Ibonrouge (I'hunnus ignore stonn. No adverse aller-etlects States Department of the Interior, thynnus Linne). In Rapport of hurricane noted this week. Salt Washington, D.C. 47(51):241-244. d' ensemble sur les travaux de I'Office Water Sportsman, Boston ]4(24): 1-3. Mason, J. M. Jr. 1975. U.S. Atlantic Scientifique et Technique des Peches Lozano Cabo, F. ]957. Notes on the bluetin tuna tagging, October, 1971 Maritimes de 1945 a 1953. Recherches biology and fishing oftuna. Proceed- through October, 1974. International sur les poissons. Revue des Travaux ings and Technical Papers, General Commission for the Conservation of de l'lnstitut Scientifique et Technique Fisheries Council for tlle Mediterra- Atlantic Tunas, Madrid, Collective des Peches Maritimes, Paris 18(2- nean, Rome 4(17): 113-125. Volume of Scientific Papers 4: 133- 4):65-67. 140. Lozano Cabo, F. ]958. Los escombridos Le Gall, J.Y. 1974. Cartographie de las aguas espaftolas y marroquies y Mason, J. M., Jr., Mather, F. J., ill, and mensuelle des donnees sur I' effort et su pesea; Primera Parte. Trab,\jos del Baglin, R. E., Jr. 1977. Results of les prises de la pecherie palangriere Instituto Espaftol de Oceanografia, United States cooperative tagging of thoniere Japonaise de l' ocean Madrid 25:]-254. 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Proceedings lUldTechnical Atlantic (presented at 39th AnnuaJ National Marine Fisheries Service, Papers, General Fisheries Council for Meeting of the American Society of Seattle 71(4):1103-1105. the Mediterranean, Rome 5(9): 101- Ichthyologists and Helpetologists, San 104. Levi, D. 1977. Summary report on Italian Diego, California 19 June 1959) 1-9 tuna fisheries in the Adriatic Sea. Lozano Cabo, F. ]970. Etude particuliere (mimeo). International Commission for the de la biologie des thonides du plateau Matller, F. J., ill. 1960. Recaptures of Conservation of Atlantic Tunas, continental du Maroc Atlantique. In tuna, marlin and sailfish tagged in the Letacounoux, R. and Went, A. E. J. Madrid, Collective Volume of western North Atlantic Copeia, Scientific Papers 6(2 ):256-258. (editors). Symposium surles Philadelphia (2): 149-161. Ressources Vivantes du Plateau LiGreci, F. 1961. Osservazioni compiute Continental Atlmltique Africain du Mather, F. 1.,III. 1962a. Transatlantic nella tonnara del "Tono" di Milazzo migration of two large bluefm tuna. durante la stagione di pesea 1958. Detroit de Gibraltar au Cap Vert. Rapports et Proces-verbaux des Joumal du Conseil, Copenhague Bollettino di Pescll, Piscicoltum e 27:325-327. Idrobiologia, Roma 14(n.s. )2:210-229. Reunions, Conseil international pour l'Exploration de la Mer, Copenhaguc Mather, F. J., ill. 1962b. Distribution and Lima Dias, M. and Barraca, Y. F. 1972. 159: 191-]93. migrations of North Atlantic bluefm Portuguese national report. 1. tuna. Proceedings of the Seventh Considemtions on tuna fisheries olT LUluu!mn.M. 1959. Die deutschc thuntischcrei lInd ihre t1ingcin den International Gdme Fish Conference, the coast of Continental Portugal and Gdlveston, Texas, November 15, tIle Islands of Madeira and the Azores jahren1956 bis 1958. Archiv fUr Fischereiwissenschafl, Brmmschweig 1962, 11le Institute of Marine Science, between 1961 Imd 1970. International University of Miami: 1-7. 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155 Mather, F. J., m. 1963. Tags and tagging Mather, F. J., III and Mason, J. M., Jr. tion particularly in the genus Thunnus. techniques for large pelagic fishes. 1973. Summary of recent information Fishery Bulletin, U.S. National Marine futernational Commission for the on taggings and tag returns for tunas Fisheries Service, Seattle 70( I): 1-1 2 NorthwestAtlantic Fisheries, Special and billfishes in the Atlantic Ocean. Maurin, C. 1964. The development of the Publication No.4 North Atlantic Fish futernational Commission for the fisheries in the Gulf of Lions. Marking Symposium, Woods Hole, Conservation of Atlantic Tunas, Proceedings and Technical Papers, Mass., May, 1961, Dartmouth,N.S., Madrid, Collective Volume of General Fisheries Council for the Canada (46):288-293. Scientific Papers 1:501-53l. Mediterranean, Rome 7(36):365-370. Mather, F. J., m. 1964a. Tunas (genus Mather,F. J.,m, and Mason, J. M., Jr. Meyer-Waarden, P. F. 1959. Relation' Thunnus) of the Western North 1976. Results of United States between the tuna populations of the Atlantic, Part II - Description, cooperative tagging of Atlantic bluefm Atlantic, Mediterranean and North comparison and identification of tuna, October 1974 through October Seas. Proceedings and Technical species of Thunnus based on e>..1ernal 1975. futernational Commission for Papers, General Fisheries Council for characters. Proceedings of the the Conservation of Atlantic Tunas, the Mediterranean, Rome 5(22): 197- Symposium on Scombroid Fishes held Madrid, Collective Volume of 202. at Mandapam Camp from Jan.12-15, Scientific Papers 5(2):307-312. Miyake, P. M. 1975. ICCATConserva- 1962, Symposium Series 1, Marine Mather, F. J., m and Schuck, H. A. 1960. tion measures for bluefm tuna. Biological Association offudia, Growth of blue fin tuna oftllewestern futernational Council for the Explora- Mandapam Camp, South fudia, Part I, North Atlantic. Fishery Bulletin, Fish tion of the Sea, Copenhagen, C.M. 395-410. and Wildlife Service, United States 1975/J:21 Pelagic Fish (Southern) Mather, F. J., m. 1964b. Tunas (genus Department of the Interior, Washing- Committee 1-3 (mimeo). TIIUIInUS) of the Western North ton, D.C. 179(61 ):39-52. Miyake, P. M. 1976. Preliminary report Atlantic, Part m - Distribution and Mather, F. J., III, Bartlett, M. R. and on Italian tuna catches. International behavior of Thwmus species. Beckett, J. S. 1967. Transatlantic Commission for the Conservation of Proceedings of the Symposium on migrations of young bluefin tuna. Atlantic Tunas, Madrid 1-7 (mimeo). Scombroid Fishes held at Mandapam Journal ofthe Fisheries Research Miyake, M. P. and Manning, J. 1975. Camp from Jan. 12-15, 1962, Board of Canada, Ottawa futernational Commission for the Symposium Series 1, Marine 29(9): 1991-1997. Biological Association offudia, Conservation of Atlantic Tunas, Mather, F. J., ill, Mason, J. 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157 Piccinetti, C., Piccinetti Manfrin, G. and scombrids taken by tcms in the Dry Repllblica Portugllesa. 1968. Estatistica<; Dicenta, A. 1976b. Premieres l'eches Tortugas, florida. Bulletin ofMarinc das pcscas maritimas no contincnte e" quantitatives de larves de thonides en Science, Miami 20(2):389-413 ilhas adjacentesno ano de 1967. Adriatique. Conunission intemationale Presley, R. F. 1972. Plankion, nekton and Direcyilo das Pescarias, Lisboa: 52. pour l'Exploration Scientifique de la nightlight collections with pertinent Republica Portuguesa. 1969. Estatisticas Mer Mediterranee, Monaco, 25~ data. Hourglass cruises, Gulf of das pescas maritimas no continente e Congres-Assemblee Pleniere de Split, Mexico (1965-1967). Florida ilhas adjacentes no ano de 1968. 22-30 Octobre 1976. Comite des Department of Natural Resources Direcyao das Pescaria<;,Lisboa: 52. Vertrores marins et Cephalopodes, 1-2 Marine Research Laboratory, St. Republica Portuguesa. 1970. Estatisticas (mimeo). 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158 Richards, W. J. 1974. Preliminary the Conse1Vation of Atlantic Tunas, Commission for the Conse1Vation of estimation of the size of the spawning Madrid, SCRS/77/47: 1-2 (mimeo). Atlantic Tunas, Madrid, Collective stock ofbluefm tuna in the Gulf of Richards, W. J. and Simmons, D. C. Volume of Scientific Papers 6(2):270- Mexico. National Marine Fisheries 1971. Distribution of tuna larvae 280. SelVice, Southeast Fisheries Center, (pisces, Scombridae) in the northwest- Rivas, L. R. 1977b. Age composition, Miami (mimeo): unpaginated; ern Gulf of Guinea and off Sierra seasonal distribution of age groups, Richards, W. 1. 1976. Spawning of Leone. Fishery Bulletin, U.s. National and longevity in the Western North bluefm tuna (Thunnus thynnus) in the Marine Fisheries Se1Vice,Seattle Atlantic bluefin (Thunnus thynnus). Atlantic Ocean and adjacent seas. 69(3):555-568. International Commission for the International Commission for the Richards, W. J. and Wise, J. P. 1969. 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1M Vilela, H. and Monteiro, R 1959. Sobre Wathne, F. 1959. Summary repOit of Wilson, P. C. and Bartlett, M. R. 1967. atims de Angola. Boletirn da Pesca exploratory long-line fishing for tuna hlVentory of U.S. exploratory longline Lisboa: 12(64): II-54 (Comuni~ao ao in the Gulf of Mexico and Caribbean fishing effort and catch rates for tunas coloquio sobre oceanografia e pescas Sea, 1954-1957. Commercial Fisheries and swordfish in the northwestern Maritima na costa ocidental da Africa, Review, U.S. Fish and Wildlife Atlantic 1957-1965. U.S. Fish and Luanda, 1957; translated into English SeIVice, Washington, D.C. 21 (4):1-26. Wildlife Special Scientific Report- by Wise J. P.- Translation No.5 of Watson, M. E. 1964. Tunas (genus Fisheries. 543:1-52. the U.S. Bureau of Commercial Thunnus) of the western North Wilson, R. C. 1953. Tuna marking, a Fisheries, Tropical Atlantic Biological Atlantic. Part I. Key to the species of progress report. California Fish and Laboratory, Miami, Florida, 1965). Thunnus based on skeletal and visceral Game, Sacramento 39(4):429-442. Vile1a, H. and Monteiro, R. 1961. Etudes anatomy. Proceedings of the Sympo- Wise, 1. P. and Davis, C. W. 1973. sur 1abio10gie et la peche des thons sium on Scombroid Fishes held at Seasonal distribution oftunas and Thunnus thynnus L. - des cotes Mandapam Camp from Jan. 12-15, billfishes in the Atlantic. NOAA portugaises 1960-61. Conseil 1962. Symposium Series I, Marine Teclmical Report, U.S. National permanent international pour Biological Association ofIndia, Mariner Fisheries SeIVice, Seattle, l'Exp10ration de la Mer, Scombriform Mandapam Camp, South India Part I Special Scientific RepOit-Fisheries Fish Committee 146: 1-6. 389-394. 662:1-24. Vilela, H. and Pinto, J. S. 1958. Sur les Watson, M. E. and Mather, F. J., Ill. Wise,J. P. andLeGuen,J. C. 1969. The thollS qn' on peche au Portugal. 1961. Species identification of Japanese Atlantic longline fishery, Conseil permanent international pour juvenile tunas (genlls TllUlmus) from 1956-1963. Proceedings of the l'Exploration de la Mer, Copenhague the Straits of Messina, northwestern Symposium on the Oceanography and C.M. 1958 Comite des Poissons Atlantic and the Gulf of Mexico Fisheries Resources ofthe Tropical Scombrifonnes 84: 1-7. (presented at the Pacific Tuna Biology Atlantic, Review Papers and Contribu- Vinciguerra, D. 1896. Relazione intorno Conference arranged by the U.S. tions, UNESCO, Paris 26: 317-347. Bureau of Commercial Fisheries, alIa pesca di acqua dolce e di mare in Young, E. B. 1975. Canadian statement Honolulu, Hawaii, August 14-19 Sicilia e ai modi fer aumentare il for Panel 2, Regular meeting of (1961): 1-4 (mimeo~aphed). frodotto. Bolletino di Notizie agrarie ICCA T Council, Madrid, November del Ministero diAgricoltura, Industria Westman,J. R. and Gilbert, P. W. 1941. 22, 1974. International Commission e Commercio, Roma 18,2 sem Notes on age determination and for the ConseIVation of Atlantic (29): 112-128. growth of the Atlantic bluefin tuna, Tunas, Madrid, Report for biennial Vodyanitskii, V. A. 1936. ObseIVations Thunnus thynnus (Linnaeus). Copeia, period, 1974-75, Part I (1974) English on pelagic eggs of fishes of the Black Philadelphia 2:70-72. Version 50-53. Sea. Trudy,AkademiiaNaukSSSR; Westman, J.R and Neville, W. C. 1942. Zharov, V. L. 1965. Results ofthe Sevastopolskaia Biologicheskaia The tuna fishery of Long Island, New fomth scientific-exploratory tuna Stlintsiia, 5:3-43 (in Russian with York. A survey conducted by the expedition into the tropical Atlantic. German summary; translation into United States Department of the In Bogdanov, A. S. (Editor), Soviet- English of pages 23-26 on eggs and Interior, Fish and Wildlife SeIVice, in Cuban Fishery Research, Izdatelstvo early laIVae of l1lUnnus thynnus cooperation with the County Execu- "Pishchevaya Promyshlennost," [Orcynus thynnusJ by W. L. Klawe, tive and the Board of Supervisors, Moskva 1965. Translated from Inter-American Tropical Tuna Nassau County, Long Island, New Russian, Israel Program for Corrunission, La Jolla, California. York. Board of SupeIVisors, Nassau Scientific Translations, Jerusalem Vodianitskii, V. A. and Kazanova, I. I. County, Long Island, New York: 1-31. 1969,172-178. 1954. Diagnostic descriptions of the Wilson, P. C. 1960. A small-boat tuna eggs and 18IVaeof the Black Sea long-line fishery. Commercial fishes. Trudy, Vsesoyuznyi Nauchno- Fisheries Review, U.S. Fish and Issledovatel'skii Institute Morskogo Wildlife SeIVice, Washington, D.C. Rybnogo Khozyaistra I Okeanografii 22(9):8-13. (VNIRO), 28:240-323 (in Russian; Wilson, P. C. 1965. Review of the translation of sections pertaining to development Atlantic coast tuna bonito and bluefm tuna by W. L. fishery. Commercial Fisheries Klawe, Inter-American Tropical Tuna Review, U.S. Fish and Wildlife Commission, La Jolla, California. Service, Washington, D.C. 27(3):1-]0.

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