PREFACE

The main task of editing papers from a Symposium original title also did not include the words “and is to ensure that they are published as soon as possible adjacent seas” but as many of the papers deal with after the meeting. However, the conclusions and species which do not occur in Arctic waters, the recommendations of this Symposium highlight the addition of a few words to the title seems more lack of knowledge of some potentially valuable fish. desirable than deletion of a number of papers. Because of this, important data have been added to For the sake of uniformity, wherever possible the some papers during editing, and several verbal reports scientific names used are those published in ICES to the meeting have been included in this volume at Bulletin Statistique, Vol. 49 for 1964 (Copenhagen 1966). the request of the Symposium. Thanks to the willing I would like to thank Dr. E.M. P o u l s e n for his help cooperation of the authors the amendments and editing and advice both at the meeting and during the editing have not unduly delayed its preparation for publi­ of this volume, and Mr. R . J. W o o d and others who cation. have helped in sorting out the discussion notes. The terms of reference excluded consideration of Finally, Miss R o se B e d f o r d and her assistants of the the herring, redfish and some other pelagic species Fisheries Laboratory must also be thanked for checking which are already exploited wherever they occur. The the typescripts and proofs. R. W. Blacker Editor and Rapporteur

INTRODUCTION

At the Statutory Meeting of the International Mr. R. W. B l a c k e r was asked to act as Rapporteur, Council for the Exploration of the Sea in 1963 the and he accepted this task. Distant Northern Seas Committee and the Gadoid Thirty-eight experts from member countries, from Fish Committee presented to the Council recommen­ Canada and USA as well as from international dations that a Symposium be organised on the organisations connected with fisheries and marine “Ecology of Pelagic Fish Species in Arctic Waters”. researches participated in the Symposium. These recommendations were renewed in 1964, and Twenty-one papers had been submitted and during Dr. E r ik M. P o u l s e n was nominated Convenor of the Symposium four additional contributions were the Symposium. A Steering Committee including the given verbatim, these latter are also included in the Convenor and the Chairmen prepared a programme present publication of the contributions. for the Symposium in which the main lines of the Furthermore, two synopses, one on Norway pout Symposium were designed as follows and the other on poutassou prepared for FAO by Mr. D. F. S. R a i t t were submitted to the Symposium (a) The significance of the pelagic fish within the for comments. These two synopses were considered food-chains in the Arctic and the role of these and comments on them were given. The Symposium species as food for the most important commer­ expressed the wish that the preparation of these highly cial fishes, useful synopses be continued by FAO to include also (b) Migration and distribution of the pelagic fish in other fish species of commercial interest in the Arctic Arctic waters and their relationship with and in adjacent regions. distribution and movements of the main commer­ The scientific papers for the Symposium were cial fishes, considered (reviewed by authors or other experts) in (c) The biological basis for fishery of pelagic fish in the following order in accordance with the Agenda: the Arctic. 1 - General (occurrence), 2 - Capelin, 3 - greater In the 1965 Statutory Meeting the Distant Northern silver smelt, 4 - smelt, 5 - Norway pout, 6 - Blue Seas Committee prepared a Preliminary Programme whiting, 7 - Polar cod, 8 - Navaga, and 9 - General for the Symposium. (food interrelations). The Recommendations on the Symposium were After each of these items a consideration and discus­ adopted by the Consultative Committee and the sion of the pertinent papers took place. Council, and the Symposium was convened on Thereafter followed a general discussion of the main September 30th and October 1st, 1966, at Charlotten- subject, as follows :— lund Castle in connection with the Statutory Meeting 1. The species as links in food-chains; discussion- of that year. leader: D. V. R a d a k o v , U S S R . 143

SECTION 9: General Biology

1. FOOD INTERRELATIONS OF PELAGIC FISH IN THE NORTHERN SEAS

By

G. V. N ik o l s k y & D. V. R a d a k o v A. N. Severtsov Institute of Animal Morphology USSR Academy of Sciences

Because of the intensified utilization of the World complex, i. e. a group of species of a common geo­ Ocean fish resources, which in some regions results graphic origin. According to most researchers, there in overfishing, the problem of increasing the pro­ are the following faunistic complexes in Arctic and ductivity of commercial fish populations and of the North Atlantic seas (A n d r i y a s h e v , 1954; N ik o l s k y , whole fishing areas has become more and more acute 1947): to researchers. One of the important methods of A r c t i c : Boreogadus saida, Liopsetta glacialis, Myoxo- increasing the productivity of a waterbody is known cephalus quadricornis ; to consist of controlling the food interrelations of fish B o r e o -A r c t ic : Mallotus villosus, Osmerus eperlanus, by shortening food-chains, abolishing “trophic dead Eleginus navaga, and others; ends”, and using some other ways of interference with B o r e a l : Clupea harengus, Gadus morhua, Melanogram- the process of organic matter formation and trans­ mus aeglefinus, Pollachius virens, Pleuronectes platessa, formation in a water body. In order to succeed in Platichthys flesus, Myoxocephalus scorpius, and others; working out effective methods of biological amelior­ C e l t i c : Sprattus sprattus, Merlangius merlangus, Tri- ation by reconstructing food interrelations in a water sopterus esmarkii, Psetta maxima; body, the knowledge of the regularities to which those M editerranean : Sardina pilchardus, Engraulis encrassi- interrelations are submitted is of primary importance. cholus, Scomber scombrus, Scomber japonicus ( = Pneumato- By pelagic fish we mean the fish adapted to life in phorus colias), Sarda sarda, Solea solea, and others. water layers and for a considerable part of their life unconnected with the bottom. Most of the pelagic Complexes of lower latitudes are not considered in fish are pelagophilic, producing floating eggs, only the present paper though some species from those in the Arctic and boreal zones are there rather large complexes, for instance flying fish, sometimes pene­ percentages of pelagic fish producing eggs on the trate far to the north. bottom. While the faunistic complexes are defined rather As to feeding, the pelagic fish are either plankton distinctly for the pelagic fish of the upper layers in eaters or predators. They mostly feed far from the northern seas (A n d r i y a s h e v , 1954; N i k o l s k y , 1953, shores. However, typical pelagic fish such as the 1965, and others), our data on the bathypelagic fauna Polar cod (Boreogadus saida) are closely connected with are still insufficient. the coastal zone in Arctic seas. On the one hand, they As has been shown by one of the authors (N ik o l ­ consume shore organisms and sometimes even fresh­ s k y , 1947, 1953), a specific system of food interrela­ water organisms occurring in the brackish zone; on tions develops within every faunistic complex during the other hand, the pelagic fish of the open sea when the process of evolution. Major adaptive relations take approaching shores, in their turn, come under the place “along the vertical” predator-prey, food-con- action of shore predators, for many of them the bulk sumer. An element of the food-chain referred to as of their food usually consists in bottom organisms. triotrophus by M a n t e u f e l ( 1961 ) has its specific features Thus, when studying the regularities of the food within every faunistic complex. The specific features interrelations of the pelagic fish in Arctic seas, their include, first of all, the tension of food relations in­ food relations with shore organisms should also be fluencing the intensity of the development of protect­ taken into consideration. As is known, the character ion organs of prey and accordingly catching adaptations of feeding and the main peculiarities of the food of predators. Besides, the fecundity of representatives interrelations of a species are formed in the period of of more southern faunistic complexes is usually higher, its origin, in the process of the formation of a faunistic contributing to a species’ survival under higher 144

Table 9:1. Predatory fish species. Number and percentage in the ichthyofauna of northern seas (The table is made for mature specimens only) - (After Andriyashev with some additions)

Seas Laptev K ara White Barents North

P red ato rs...... 6 (10-3»/.) 14 (13-7%) 41 (20-0°/„) Predators-plankton e a te rs ...... 1 (3-1%) 1 (2-5°/0) 6 (10-3%) 7 (6-9 °/0) 25 (12-1%) Total number of species ...... 32 40 58 102 206

mortality rates. In the faunas of some seas the repre­ to low latitudes which is an instance of a correspond­ sentatives of the different faunistic complexes do not, ing regularity taking place on the global scale. however, live separately, but often come into contact As is seen from Table 9:2, the relative portions with the representatives of other complexes with cer­ of pelagic fish in Arctic seas is almost four times lower tain food interrelations naturally arising. While within than in the Norwegian Sea. a faunistic complex similar feeding leads to reduced The third peculiarity of fish-food interrelations in tension of food interrelations between species, one of northern seas to be considered is connected with the the main forms of food interrelations between the relations between the pelagic ichthyofauna of the species belonging to different complexes is based just open part of the sea and of the shore. In Arctic seas on the similarity of their food composition. of high latitudes most of the inhabitants of the pelagic We are now going to discuss in detail the regulari­ zone are very closely connected in their food inter­ ties of food interrelations in the pelagic zone of Arctic relations with the fish of the coastal zone and in some seas. As already mentioned, the influence of predators cases even with the generatively freshwater fauna. So, on the population of pelagic fish eating zooplankton in the Laptev Sea, the representatives of freshwater is reduced in seas of high latitudes. Changing of and migratory fish play an important part in the food percentages of pelagic predators in some Arctic sea of the Polar cod (P i r o z h n i k o v , 1955) consisting there fauna is but natural. In high Arctic seas like the of Stenodus leucichthys nelma 3-6 °/0; Coregonus sardinella Laptev and Kara Seas there are hardly any predatory — 92-5 °/0; C. autumnalis — 57-2 °/0; C. muksun - 4-2°/0, fish (Table 9:1). and Osmerus eperlanus — 3-6 °/0 ,as is found in the sto­ Though the data are rather tentative, relatively machs filled with such kind of food. As to inverte­ higher amounts of predatory fish in the seas of lower brates the Polar cod in estuaries mostly consume latitudes are demonstrated clearly enough. In the Copepoda. The composition of invertebrates in the Laptev and Kara Seas there are no typical predators, food of the Polar cod is most of all like that of Coregonus while partially predatory fish with plankton being a autumnalis and Coregonus sardinella. Another plankton substantial portion of their food, consume great eater of the Laptev Sea occurring there rather rarely amounts of the fry of generatively freshwater fish, is the capelin (Mallotus villosus) which mainly con­ such as smelts, whitefishes, etc. In the White Sea, and sumes Mysidae eaten by the generatively freshwater particularly in the Barents Sea, true predators appear, fish of the Laptev Sea in insignificant quantities. The all of them representing the boreal or even more south­ Polar cod, especially fry, are in their turn consumed ern complexes. Within the Arctic and boreo-Arctic by a number of semi-migratory predators. In estuaries faunistic complexes there are no true predators. the Polar cod in some seasons is the basic food of Another peculiarity of the fauna of the Arctic seas nelma (Stenodus leucichthys nelma), ling (Lota lota) and is that in pelagic fish percentages increase from high other predators.

Table 9:2.

Pelagic fish percentage (to the total number of species) in Arctic seas. (After A n d r iy a s h e v )

SW part of Siberian Seas White Sea Norwegian Sea North Sea Barents Sea

Pelagic species...... 4 (8-7%) 7 (12-1%) 12 (17-9%) 53 (30-0%) 33 (16-0%)

Total number of species ...... 46 58 67 177 206 145

Thus, the data cited stress the above-mentioned 1. Predators’ importance in ichthyofauna grows from regularity; tension in food relations between different high to low latitudes. faunistic complexes (here Arctic marine and generat­ 2. The greatest tension in food interrelations due to ively freshwater complexes) becomes highest in cases the consumption of similar food occurs between the of similar food consumption. species of different faunistic complexes, which, how­ In the Kara Sea the pelagic fish of the high sea ever, occupy similar ecological niches. are to a smaller degree but still rather closely connected 3. In high Arctic seas and in the White Sea there with the fish of the coastal zone, particularly of the exists a close food interrelation between the fish of the estuary; their food interrelations in the Kara and pelagic and coastal zones, estuaries in particular. So Laptev Seas are alike. the food supply of pelagic fish accordingly increases In the White Sea with an ichthyofauna more varied at the expence of the food resources of the coastal in composition and mixed with boreal elements, food zone. interrelations are naturally more complicated. Major 4. In deep-water seas there are also food interrelations clashes due to the consumption of similar food take between the fish of the pelagic zone and the bathyal place here between the herring (Clupea harengus fish; they occur both up to the predator-*■ prey relat­ marisalbi) smelt (Osmerus eperlanus) and the three- ions and due to similar food consumption. spined stickleback. Capelin usually occurs in the White 5. The knowledge of the food interrelations of the Sea in rather small amounts, appearing in mass fish in the pelagic zone is necessary for creating quantities only occasionally. As a rule, capelin has efficient fisheries to allow for a control of the commer­ no influence on fish food interrelations. The Polar cial fish-stock productivity. cod gets into the White Sea in considerable amounts The present paper deals with the food interrelations in cold years only. Its feeding spectrum (M a n t e u f e l , of the fish in the pelagic zone of the Arctic seas only 1943) may partially coincide with that of Eleginus in a most general way. To start working out the me­ navaga. To some extent it is also similar to the food- thods of controlling fish productivity in the northern composition of Gadus morhua maris-albi and herring. Atlantic, further knowledge is required as to the In the Barents Sea the fish of the pelagic zone are character of the biotic relations, particularly the food much less connected in their food interrelations with interrelations between the fish of different faunistic shore fish as compared with the seas mentioned above. complexes including the fish of the bathyal zone. Within the boreal complex the major pelagic fish, i. e. plankton-eating herring and the predators, REFERENCES — saithe (Pollachius virens) and cod (Gadus morhua), are Andriyashev, A. P., 1954. “The fishes of the northern seas of primarily connected by the direct relations predator-s- the USSR”. Keys to the fauna of the USSR No. 53. Academy prey and food ^consumer. Only specimens belonging of Sciences of the USSR, Moscow-Leningrad. (Israel Program to younger age-groups have similar food-composition. for Scientific Translations No. 836, Jerusalem 1964). At the same time “competitive” relations are peculiar Gordeyeva, K. 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