The diet of the tained from a longline vessel between 1 and 15th March 1991 by using Xiphias gbdius Linnaeus, mackerel, Scomber spp., as bait.

1 758, in the central east Atlantic, Zone C Gulf of Guinea (3O09'- 0°36'N and 26O27'-4O17'W). Fifteen with emphasis on the role of swordfish (standard length [SL] between 140-209 cm) were selected on the basis of the presence of cephalopods in their stomachs. Vicente Hernández-García These were taken from catches Dpto de Biología, Facultad de Ciencias del Mar made by a longliner between May Univ. de Las Palmas de G. Canaria and July of 1991 by using mackerel C P 350 1 7, Canary Islands, Spain and , Illex sp., as bait.

Stomach preservation and analysis

The swordfish Xiphias Stomach content analysis is an In zones A and B, fish were stored Linnaeus, 1758, is a mesopelagic important tool in ecological and in ice. After landing, fish were mea- teleost with a cosmopolitan distri- fisheries biology studies. Oceanic sured from the tip of the lower jaw bution between 45"N anci 45"s iati- vertebrates are often more efficient to the fork of the taii (S¿). During tude. It is an opportunistic preda- collectors of cephalopods than any commercial operations the internal tor feeding mainly on pelagic ver- available sampling gear (Bouxin organs were removed before the tebrates and invertebrates (Palko and Legendre, 1936; Clarke, 1966). fish were weighed. The stomach et al., 1981). The diet. of the sword- The p'irpose nf thir st11dy was to rnntents nf earh fish, incli~dingal1 fish has been studied mainly in the expand knowledge of the diet of the hard parts found in the stomach western Atlantic Ocean (Tibbo et swordfish from the central east At- wall folds (otoliths, very small al., 1961; Scott and Tibbo, 1968, lantic Ocean, with special emphasis beaks, and lenses), were weighed 1974; Toll and Hess, 1981; Stillwell on the role of species. (in grams) and preserved in 70% and Kohler, 1985). Earlier reports ethyl alcohol. Otoliths were also reflected the importance of fish in removed from the fish prey. Nema- the swordfish diet, but recently Material and methods todes were found in some stomachs Stillwell and Kohler (1985) cited in small quantities, but these were squid as the predominant compo- Sampling areas and capture assumed to be parasites and were nent in the diet of swordfish. methods not considered prey. In general, Azevedo (1989) and Moreira (1990), stomach contents showed an ad- reporting from off the Portuguese The stomach contents of 75 sword- vanced leve1 of digestion. A stomach coast, mentioned fish (principally fish, Xiphias gladius, were ana- fullness index (SF)was calculated as M~icromesistiuspoutssou)and cepha- lyzed. Specimens were caught at SF = (wet weight of'the stomach con- lopods as the main prey groups of night in three different areas of the tent / wet weight of the swordfish swordfish. This finding was cor- central east Atlantic Ocean (Fig. 1) without internal organs) x 100. roborated by Guerra et al. (1993) from the commercial landings of the In zone C only cephalopods were frnm the N~rtheasternAtlantic Ypanirh fleet: preserved fr~zefi.Fish WPE frnzm where cephalopods were found to immediately after capture without be the most important component Zone A Strait of Gibraltar internal organs. This material was of the diet. Maksimov (1969) stud- (35O53'-35O42'N and 6O35'-6"30'W). not included in comparative analy- ied the diet of swordfish in the east- Thirty five swordfish were caught ses because the main objective was ern tropical Atlantic Ocean. Cepha- with drift nets (2.5 miles long x 20 to record the relative proportions of lopods were a major component of m deep) between 10 and 22 Septem- cephalopod species that were preyed the diet in al1 areas sampled and ber 1990. upon in this zone. although no cephalopod species Scomber spp. and Illex sp. were were identified, the genus Omma- Zone B South of the Canary Is- not considered prey from zones B strephes was present among the five lands (23O-26ON and 17O-22OW). Manuscript accepted 17 November 1994 genera found in stomach contents. Twenty-five swordfish were ob- Fishery Bulletin 93:403-411 (1995). 404 Fisherv Bulletin 93121. 1995

the hood length (LHL)(defined in Clarke, 1962,1980) were measured by digital caliper or steroscopic mi- croscope and eyepiece micrometer. lengths (ML in mm) and weights (W in g) of the cephalopods from which lower beaks came were then estimated from LRL's or LHL's by using relationships published elsewere (Clarke 1962,1980,1986a;Pérez-Gándaras, 1983;Wolff, 1982 (cited by Clarke, 1986a),Wolff and Wormuth, 1979). Despite the advanced state of digestion of stom- ach contents, an attempt was made to examine the importance of each prey item. Two methods of stom- ach content analysis were used: percent numerical abundance and percent occurrence (Hyslop, 1980).A coefficient of prey numerical frequency, % No. = (Ni1 Ntj x 100, and a coefficient of prey frequency, % oc- currence = (NsilNsfl x 100 were calculated; where Ni is the number of prey of each group i, Nt is the total number of prey, Nsi is the number of stomachs containing each group i, and Nsf is the total number of stomachs with food. An index of prey numerical importance (Castro, 1993) was also obtained as 9% a -N importance = (% No. x 92 oc~urrence)~'~x 100. = Om -

- Comparative analysis of degradation of hard m0 structures E

Free hard structures (otoliths, beaks, and eye lenses) Zone C -7 - %*e%&+>* % were often found in the stomach contents. To esti- mate the importance of each prey item from the re- fractor~or hard structures, it is important to know Figure 1 the rate of degradation by stomach acids. Locations of the swordfishXiphias gladius fishing grounds Otoliths (sagittae) from four chub mackerel, in the central east Atlantic Ocean where samples were Scomber japonicus (18 to 20 cm SL), similar in size obtained in 1990-91. to those found in the swordfish stomachs, and five otoliths of blue whiting, Micromesistius poutassou, from head-specimens found in swordfish stomachs and C respectively because they were used as bait. were used to determine the rate of otolith degrada- pley items weiee ideiliifled to the Iowesi ~axoiioiiiic A: -.- ~L-I:LL 1 -- LL - L-I--- -.-LL - i -.----L -..:,. ...-.-- LIUII.w LUIILII 1e11gLIIS, Lanell u11 LII~IUII~~S L axis, ~el-e category possible. Fish were identified from otoliths between 3.70 and 4.10 mm for Scomber and between and bones (otolith guides of Harkonen (1986), Hecht 10.81and 13.53 mm for Micromesistius. Beaks from and Hecht (1979), and author's collection). Crusta- eleven Zllex coindetii and two Todarodes sagittatus ceans were classified from externa1 parts of the skel- were used, with LRL's between 3.90 and 6.19 mm eton (Zariquiey-Alvarez, 1968). Lower beaks (LB) and 7.53 and 8.41 mm, respectively. Degradation of were used as the primary means for classification of six eye lenses, three belonging to T sagittatus and cephalopods, and beak identity was established by three belonging to fish species, were also analyzed. methods described by Clarke (1962,1980,1986a) and Hard structures were placed in a hydrochloric acid supplemented by a collection of cephalopod beaks (in- (HC1) solution (pH=l.l;value lower than the range cluding beaks removed from locally caught cephalo- reported by Jobling and Breiby 119861 for fish in pods); upper beaks, other morphological characters which the digestive process had begun), and the tem- (Hess and Toll, 19811, and distributional knowledge perature was maintained between 18 and 20°C. The (Nesis, 1987)were used in some cases as well. Nearly experiment was carried out for 48 hours. Old acid solu- al1 the beaks collected were fresh. Al1 lower beaks tions were replaced with fresh solutions after 24 hours. were identified to the lowest taxon possible and the digestion (measured as decreas- lower rostral length (LRL) or, in the order Sepiida, ing upper rostral length, lower rostral length, and NOTE HernAndez-Garcia. Diet of Xph~asglad~us 405

lower wing length) and eye lens digestion (measured nal column (as long as 78.5 cm). It was estimated as decreasing lens diameter) were measured every that otoliths and spines belonged to a total of 476 12 hours. Otolith digestion (measured as decrease of fish. Blue whiting, Micromesistiuspoutassou, was the the longest axis length) was measured at intervals most important prey species by number (37.81%, of 12 hours for blue whiting, although the third in- Table 3). terval was divided into two intervals (measuring each Cephalopods were detected in 17.14%of the stom- 6 hours). Otolith digestion was measured at inter- achs sampled, and the number of specimens was es- vals of 2.5 or 1 hour for the chub mackerel. timated as 26 (Table 2). They were always present in those fish with the highest SF. The Omma- strephidae was the most important family by num- Results ber (35.6%)and Todarodes sagittatus was the pre- dominant species (23.4%). The Stomach fullness analysís ranked second in importance (21.45%)and Histio- teuthis bonnellii was the dominant species (11.4%, Data on fish length (SL), weight (W), and stomach Table 4 ). fullness (SF) from zones A and B are given in Table Decapods of the order Natantia were found in the 1. Values of SF in zone A were higher than those in stomach contents of two individuals (Table 2), and a zone B. In the latter area four stomachs were empty large specimen was identified as Acanthephyra whereas in zone A al1 stomachs had contents. purpurea.

Stomach contents analysis Zone B In zone B the swordfish diet consisted of a cephalnpodr and firh. Cephalopodi reprerented fhe N ZoneA The swordfish diet consisted of fish, cepha- most common food item in this area, revealing the g lopods, and decapods (Table 2). Fish were the most highest index of numerical importance (67.89%, Table - important item by number (93.33%, Table 21, al- 2). A group of six pairs of beaks and one free upper though in 20% of the stomachs analyzed fish were beak with the same shape could not be assigned to E represented by only otoliths and bones. A total of 832 any family. These were called "Unknown A." A " otoliths were collected. Most bone remains could not description and sketches of this beak type (Fig. 2) be identified. Many of them consisted of a large spi- are given in the Appendix. was the

2 -n

Table 1 Swordfish X~phzasgladius data from zones A and B: length (SL)in cm, weight (Wi in Kg, and stomach fullness (SF). n is the number of fish collected in each zone.

SL W SF

n Range Mean SD Range Mean SD Range Mean SD ------ZoneA 35 103-193 142.4 17.72 20-132 56.95 29.71 0.1-9.0 2.46 2.29 Zone B 25 112-201 153.3 24.54 13-102 40.40 24.36 0-5.3 0.75 1.37

Comparison of the dietary importance of the three major forage categories observed in swordfish stomachs from zones A (35 fi5h) and B (21 fish) Data are @ven in terms of numerical frequency, frequency of occurrence, and index of numerical importance ------Zone A Zone B

Q Q % l 57 57 Q

Forage category number occurrerice irnportance I Forage category num her occurrence irnportance

Fish 93 33 100 0 88 78 Fish 28 57 42 85 32 10 Cephalopods 5 09 17 14 8 54 Cephalopods 71 42 76 19 67 89 Decapod crustacea 156 5 71 2 66 Decapod crustacea 0 0 O O O O Table 3 Fish species occurring in the diet of the swordfishXiphiasgladius in zonesA and B (35 and 9 swordfish stomachs containing fish. respectively) expressed in terms of numerical frequency, frequcncy of occurrence, and index of numerical irnportance. ------Zone A Zone B -- --

Species Q number 74 occurrence % importante Species V number (/r occurrence % irnportance -- -p. ------Mzcromeszstzus poutassou 37 81 80 O0 38 61 Diaphus sp. 16 66 22 22 18 35 Scomber japonzcus 3 78 22 85 6 53 Thunnus sp. 5 55 11.11 7.49 Capros aper 2 10 8 57 2 97 Not identified 77.77 77 77 74.16 Lepzdopus caudatus 147 20 O0 3 80 Dachurus sp 1 26 14 28 2 97 Merlucczus merlucczus O 84 5 71 153 Thunnus sp O 21 2 85 O 54 Not identified 52 52 71 42 43 O0

Figure 2 Illustration of the characteristic, unidentified, lower beak (called "Unknown A"). Lower rostral length = 3.4 mm. (A) profile of the beak; (B) profile of the anterior part with one side removed to show the shoulder and the anglepoint; (C) top view; (D) outline of the beak showing the positions of sections shown in E and F; (E) three sections of the crest and one lateral wall taken at positions indi- cated in D to show thickening; and (F)two sections of the wing and shoulder region at positions shown in D. Cartilage is indicated by arrows and dotted area. NOTE Hernández-García: Diet of X~phiasglad~us 407

Table 4 Cephalopods in the diet of the swordfish Xiphias gladius from zones A, B, and C (6, 16, and 15 swordfish with cephalopod remains, respectivel~).Number of cephalopods (n),index of numerical importance (IN),range of lower rostral length (LRL),range of estimated mantle length (ML), and range of estimated body weight (W)in each zone. The percentage by number of each species in al1 areas together is also given. The equation used is given under the symbol (A)(a = Clarke, 1962; b = Clarke, 1980; c = Clarke, 1986; d = Pérez-Gándaras, 1983; e = Wolff and Wormuth, 1979; f = Wolff, 1982).A specimen identified and counted from upper beaks is indicated by an asterisk (*). Broken beaks are indicated by (R).

Zone A Zone B Zone C - -- --

Group or 4 LRL ML W q/r LRL MI. W % LRL Species n IN immi immi ig) n 1 lmm) immi (gl n IN lmm ------Family Spirulidae spirula Family Sepiidae Sepia oficinalis Family Loligo vulgaris Family Ancistrocheiridae Ancistrocheirus lesueun Family Octopoteuthidae Octopoteuthis rugosa Family Onychoteuthidae A Onychoteuthis B Onychoteuthis C Family Gonatidae Gonatus sp. ? Family Histioteuthidae bonnellii Histioteuthis dofleini Histioteuthis A Famjly Brachioteuthidae Brachioteuthis sp. Family Ommastrephidae Todaropsis eblanae Todarodes sagittatus Ommastrephes bartrami sthenoteuthis pteropus Ommastrephid species Family Thysanoteuthidae Thyanoteuthis rhombus Family Mastigoteuthidae Mastigoteuthis sp. Family Grimalditeuthidae Grimalditeuthis bomplandi Family Cranchiidae Teuthou,e,eniamegalops Teuthowenia sp. Megalocranchia sp. Family Argonautidae Aigonauta sp. Unknown A Not identified 408 Fishery Bulletin 93/21,1995

most important family by number (36.8R ), and the alditeuthis bomplandi, Megalocranchia sp., Octopo- orangeback squid, Sthenoteuthis pteropus, was the teuthis rugosa, and Spirula spirula) were identified most important species (20.6%, Table 4). for the first time in swordfish stomach contents. Eighteen fish were counted from spinal columns and otoliths with an index of numerical importance of 32.10% (Table 2). Fish were found together with Comparative analysis of hard structure cephalopods in 19.0% of the stomachs containing food. degradation In zone A the numbers of free lenses of fish and cepha- lopods were similar. However, only 32 cephalopod lenses Otoliths (sagittae) of Scomber japonicus were dis- were found in zone B; fish lenses were not found. solved after an average time of 6 hours and 47 min- utes (% decrease of otolith length=2.121 + 14.42413 Zone C A total of 46 cephalopods were found in SD=5 min; Fig. 3). Otolith length decreased signifi- stomachs from zone C. The family Ommastrephidae, cantly over a period of one hour (ANOVA, df=14, represented solely by Sthenoteuthispteropus, was the P=5.0425 x most important species by number (41.6%) and esti- Otoliths of Micromesistius poutassou showed a sig- mated weight (Table 4). The Onychoteuthidae ranked nificant decrease in length after an interval of 12 second in importance by number but not by weight. hours (ANOVA, df=8, P=1.7605 x After 48 In the combination of al1 three zones, the Om- hours, they had lost 40% of their length (% decrease mastrephidae, Onychoteuthidae, Histioteuthidae, of otolith length=1.932 + 0.84313 Fig. 3) but still and Thysanoteuthidae were the most important maintained their original shape. cephalopod families by number in swordfish diet Lower rostral length and upper rostral length did (67.9%);other families are probably occasional prey. not differ significantly after 48 hours in acid (ANOVA, g The most important species was Sthenoteuthis df=24, P=0.95588 and df=24, P=0.93221, respec- a pteropus (28.3951, Table 4). The S. pteropus collected tively). In addition, wing length of the lower beak were mostly females, as evidenced by their large MES did not differ significantly after 48 hours (ANOVA, (females can reach 650 mm ML and males 280 mm df=24, P=0.97319). No significant differences were ML, Zuev et al., 1985) and by the presence of large found for fish and lense diameter af- f oviducts. Moreover of the "Unknown A species, five ter 48 hours (ANOVA, df=4, P=0.50454 and df=4, o cephalopod species (Brachioteuthis sp., Grim- P=0.89424, respectively). -E a

2 -n

Scornber japonicus

% decrease otolith lerigth - 2 121 + 14424T f = O 9697

1 _ - - I_-- + -. . --* A, , M~crornesistiuspoutassou j - - - - % decrease otol~ltllength = 1 Y32 + O 4831

J o O 10 20 30 40 50

Time (h) Figure 3 Decrease in otolith length of chub mackerel, S~omberja~onicus,and blue whiting, Micromesistius poutassou (measured on the longest axis) after immersion in hydrochloric acid (pH=l.l)for 48 hours. NOTE Hernández-Garcia: Diet of Xloh~asalad~us 409

Discussion and Neilson (1985) and Jobling and Breiby (1986). However, the rate of degradation of otoliths in this study Commercial longline fishing generally lasts for 12- rnay be overestimated because the acidity was greater 14 hours and the fish caught can remain alive for than the value reported in general for fish stomach acids many hours (Boggs, 1992); thus digestion of stom- (pH=2.0-3.0) after the digestive process has begun. ach contents is continuous. Moreover, regurgitation Because cephalopod eye lenses and fish eye lenses are regularly occurs (Tibbo et al., 1961). This rnay bias not affected by acid, as noted by Clarke (1986b), the values of stomach fullness. The period of study was number of lenses found in a stomach rnay be a means limited in each area and sample sizes were not large, of estimating the relative importance of cephalopods precluding statistical analysis. However, the diet of and fish in the diet. However, the percentage of occur- swordfish appeared to show substantial variation rence of fish (counted from whole fish and free otoliths) between areas. In neritic areas (zone A) swordfish was similar to that obtained by Azevedo (1989) and preyed upon pelagic and benthic species of fish and Moreira (1990)in areas nearest to zone A. In zone B, if , whereas in oceanic areas ízone B) they preyed eye lenses of fish and cephalopods are considered, both mainly on squids (Table 2). This pattern was also of which experience a similar rate of digestion, the rela- observed by Maksimov (1969).In addition, Carey-and tive importance offish in the diet is less than wha t was Robison (1981) showed that in neritic areas sword- indicated by data from the otoliths. fish have a different ecology and migration pattern The importance (based on % number) of Stheno- from that found in oceanic waters. In neritic areas, teuthis pteropus in zone C is not surprising given the swordfish are found near the bottom during the day- large abundance of this species at these latitudes !ight, feeding muinly m benthic spocizs (ie. Caprcs (\&SS, 1966; Z~evet u!,, ?%5). The preferred terr.-

aper and Merluccius merluccius in this study, Table perature range for swordfish is from 25O to 2g°C -: 3); at night, they move offshore to feed actively on (Ovchinnikov, 1970) which is nearly the same as that squid and other migrating fauna concentrated near the for adult squid females (24O-30°C, Zuev et al., 1985). surface (i.e. Todarodes sagittatus in this study, Table These temperatures are almost constant at these E 4). In oceanic waters, swordfish undergo a diel vertical latitudes throughout the year. Around zone C, there migration reaching about 600 m at noon and ascend- is a complex system of currents and frontal zones ing to shallow waters at night; they can prey actively where there is a high biomass (Blackburn, 1965; n on oegopsid squids at both ends of the migration (Carey Ovchinnikov, 1970): in addition, high swordfish k and Robison, 1981). The mean number of cephalopods CPUE values have been obtained in these areas by per stomach was 0.7 in zone A, similar to data reported the Spanish fishing fleet (Mejuto et al., 1991) and by Moreira (1990).In zone B (oceanicwaters) the mean the Japanese longline fishery (Palko et al., 1981).There- $ was 1.8, similar to the value of 2.1 calculated from data fore, the availability of prey rnay be partially respon- " obtained by Guerra et al. (1993). In zone C, the mean sible for the distribution of swordfish in these waters. nurnber of cephalopds per stomach was 3. Bane (in Guerra et al. (1993) found that Sthenoteuthis Fonteneau and Marcille, 1991) also showed that cepha- pteropus was the most common species in the sword- lopod-prey are more important in oceanic waters than fish diet in the Northeastern Atlantic; this species is inshore for yellowfin tuna, Thunnus albacares. possibly one of the unidentified ommastrephid spe- From analysis of degradation, otoliths were cies found by Maksimov (1969). Todarudes sagittatus strongly eroded by acid; large, thick otoliths dissolved and Ommastrephes bartrami were also found. These more slowly than small, thin ones. Cephalopod beaks three species ascend to the upper epipelagic layer and eye lenses and fish eye lenses were not affected and feed actively on myctophids and small squid at ">,thm..xm-,7hl A"+" 1 by acid. Fish wore the item with the highest ifidcx uf night (NipatU!!in et a!., 1977; urryuui. UUUU,. numerical importance (Table 2) in zone A. However, During the day, S. pteropus descend to 350 or 400 m the value obtained must be treated with caution be- (Moiseyev, 1988). These ommastrephids have a high cause the otoliths of Micromesistius poutassou rnay growth rate and their life span is no longer than 1.5 accumulate owing to the structure of the stomach wall years (Arkhipkin and Mikheev, 1992; Rosenberg et and the time necessary to dissolve them (Fig. 3). The al., 1980; Ishii, 1977). Therefore, squid rnay be an effi- otoliths of Scomber japonicus were not found free, a cient means of energy transfer in oceanic food webs. feature that accords with the results of the analysis of degradation. Therefore, if evaluation of fish biomass is based on the presence of otoliths, biomass rnay be over- Acknowledgments estimated for fish with large and dense otoliths he. M. poutassou). Fish with smaller and weak otoliths rnay Thanks are given to F. J. Portela, Captain of the FA be underestimated as was observed by both da Silva Manuela Cervera and to J. Gutierrez for providing samples from Zone C. Thanks are also given to the Guerra, A., F. Simún, and A. E Gonzalez. staff of Algeciras Port for their help and for allowing 1993. Cephalopods in the diet of thc swordfish, Xiphias gladius, from the northeastern Atlantic Ocean. 1n me to examine swordfish stomachs there. 1 thank Okutani et al. (eds.),The recent advances in fisheries Professor Nikolai Potapuskin for his help with the biology. Tokai Univ. Press, Tokyo, Japan, p. 159-164. Russian language. Special thanks are giver? to Carlos Harkonen, T. Bas and José J. Castro for their many suggestions 1986. Guide to the otoliths of the bony fishes of the North- and helpful comments. The author is especially grate- east Atlantic. ln Danbiu ApS. biological consultants. Henningsens Allé 58 DK-2900, Hellerup, Denmark. ful to Malcolm R. Clarke for allowing me to use his Hecht, T., and A. Hecht. large collection of beaks, for the many suggestions 1979. A descriptive systematic study of the otoliths of the he offered, and for his review of the manuscript. neopterygean rnarine fishes of South Africa. Part IV: Siluriformes and Myctophiformes. Trans. Roy. Soc. S. Afr. 44:401-440. Hess, S. C., and R. B. Toll. Líterature cited 1981. Methodology for specific diagnosis of cephalopod re- mains in stomach contents of predators with reference to Arkhipkin, A., and A. A. Mikheev. the broadbill swordfish, Xiphiasgladius. J. Shellfish Res. 1992. Age and growth of the squid Sthenoteuthis pteropus 1:161-170. (: Ornmastrephidae) from the Central-East Hyslop, E. J. Atlantic. J. Exp. Mar. Biol. Eco!. 163:261-276. 1980. Stomach contents analysis-a review of methods and Azeueda, M, their aplication. J. Fish. Bid. 17:411-429. 1989. Information on the swordfish fishery in the Portu- lshii, M. guese Continental EEZ. ICCAT Collective Vol. Scientific 1977. Studies on the growth and age of the squid, Omma- Papers 32(2!:282-286. stre.~heshartrnmi (Lesiie'ir!, in tho Pacific &Jupa. BU!!. Blackburn, M. Hokkaido Reg. Fish. Res. Lab. 42:25-31. 1965. Oceanography and the ecology of tunas. Oceanogr. Jobling, M., and A. Breiby. Mar. Biol. Ann. Rev. 3:299-322. 1986. The use and abuse of otoliths in studies of feeding Boggs, C. H. habits of marine piscivores. Sarsia 71265-274. 1992. Depth, capture time, and hooked longevity of longline- Maksimov, V. P. caught pelagic fish: timing bites of fish with chips. Fish. 1969. Pitanie bol'sheglazogo tuntsa (Thunnus obesus Lowe) Bull. 90:642-658. i mmech-ryby (Xiphias gladius L.) vostochnoi chasti Bouxin, M. J., and R. Legendre. tropichesko i Atlantiki. Trudy Atlanticheskogo nauchno- i 1936. La faune pélagique de I:4tlantique au largc du Golfe issledovatel'skogo instituta rybnogo khozyaistva de Gascogne, recueillie dans des estomacs de germons. okeanografii (Trudy AtlantNIRO) XXV:87-99. IEnglish Ann. Inst. Oceanogr., Vol. XVI:1-102. Transl.: Bull. Fish. Res. Board Can. Transl. Series Carey, F. G., and B. H. Robison. KO.2248.1 1981. Daily patterns in the activities of swordfish, Xiphias Mejuto, J., P. Sánchez, J. M. de la Serna. gladius, observed by acoustic telemetry. Fish. Bull. 1991. Nominal catch per unit of effort by length groups and 79277-292. areas of the longline Spanish fleet targeting swordfish Castro, J. J. (Xiphias gladius) in the Atlantic, years 1988 to 1990 1993. Feeding ecology of chub mackerel (Scomberjaponicus) cornbined. ICCAT, Collective Vol. Scientific Papers in the Canary Islands area. S. Mr. J. Mar. Sci. 13:323- 39(2):615-6'25. 328. Moiseyev, S. V. Clarke, M. R. 1988. New data on vertical distribution of the orangeback sq..;a SCL,.-.,... &L: ; ," 1962. She ideiiiiíication of cephalopod 'beaks' and the re- IILCILVL~ULILLS IJL~~V~U~i~ephaiopociai. Eesources lationship between beak size and total body weight. Bull. and biological bases of rational use of commercial inverte- Conf Br. Mus. (,Vat. Hist.)2001. 8:419-480. brates. AII-USSR , Vladivostok, Abstr. Comnr un.: p. 89-90. 1966. A review of the systematics and ecology of oceanic Moreira, F. squids. Adv. Mar. Biol. 4:91-300. 1990. Food of the swordfi sh, .YipF,tus gludtzs Lifiiiaeüs, 190G. Cephalopoda in &e diet of sperm whaies of the south- 1758, off the Portuguese coast. J. Fish Biol. 36:623-624. ern hemisphere and their bearing on sperrn whale Nesis, K. N. biology. Discovery Rep. 37: 1-324. 1987. Cephalopods of the world. 1n L. A. Burgess (ed.),T. 1986a. A handbook for the identification of cephalopod F. H. Publications, Neptune City, NL, for the English trans- beaks. Clarendon Press, Oxford. lation. [Original in Russian.1 198%. Cephalopods in the diet of Odontocetes. In M. M. Nigmatullin, Ch. M., M. A. Pínchukov, and Bryden and R. J. Harrison (eds.), Research on dolphins, p. N. M. Toporova. 281-321. Clarendon Press, Oxford. 1977. The feeding of two background species of epipelagic da Silva, J., and J. D. Neilson. squids of the Atlantic Ocean. Irt All-union scientific con- 1985. Limitations of using otoliths recovered in scats to ference on the utilization of commercial invertebrates for estimate pey consumption in seals. Cm. J. Fjsh.Aquat. food, fodder aad technical purposes. Abstracts of Reports, Sci. 42:1439-1442. p. 58-60. [Original in Russian.] Fonteneau, A., and J. Marcille (eds.). Ovchinnikov, V. V. 1991. Recursos, pesca y biología de los túnidos del Atlántico 1970. Mech-ryba i parusnikovye (Atlanticheski okean). Centro-Oriental. ICCAT, Madrid. Ekologiya i funktsional (naya morfologiya). ( NOTE Herndndez-García: Diet of Xiphias gladius 41 1

and billfishes in the Atlantic Ocean. Ecology and functional gladius in the western North Atlantic Ocean with estimates morphology.). Nauch-Issled. Inst. Ryb. Kohz. Okeanogr., of daily ration. Mar. Ecol. Prog. Ser. 22:239-247. Kaliningrad, 106 p. [Transl. by Israel Prog. Sci. Transl., Tibbo, S. N., L. R. Day, and W. F. Doucet. 77 p., 1971; avail. U. S. Dep. Commer., Natl. Tech. Inf. Serv., 1961. The swordfish (Xiphias gladius L.), its life-history Springfield, VA, as TT71-50011.). and economic irnportance in the northwest Atlantic. Bull. Palko, R. J., G. L. Beardsley, and W. J. Richards. Fish. Res. Board Can. 130. 1981. Synopsis of the bio\ogy of the swordfish Xipkias TON,R. B.,and S. C. Hess. gladius Linnaeus. U.S. Dep. Commer., NOAATech. Rep. 1981. Cephalopods in the diet of the swordfish, Xiphias NMFS Circ. 441. gladius, from the Florida Straits. Fish. Bull. 79:765-774. Pérez-Gándaras, P. G. Voss, G. L. 1983. Estudio de los cefalópodos ibéricos: sistemática y 1966. The pelagic mid-water fauna of the eastern tropical binomia mediante el estudio morfométrico comparado de Atlantic with special reference to the Gulf of Guinea. Zn sus mandíbulas. Tesis Doctoral, Univ. Cornplutense de Proceedings of the symposium on the oceanography and Madrid, Madrid. fisheries resources of the tropical Atlantic, Adidjan, Ivory Rosenberg, A. A., K. F. Wiborg, and 1. M. Bech. Coast, 20-28 Oct., p. 91-99. 1980. Growth of Todarodes sagittatus (Lamarck) (Cepha- Wolff, G. A. lopoda, Ommastrephidae j from the Northeast Atlantic, based 1982. A study of feeding rclationships in tuna and porpoise on counts of statoliths growth nngs. Sarsia 66:53-57. through the application of cephalopod beak analysis. Scott, W. B., and S. N. Tibbo. Final Tech. Report for DAR-7924779, Texas A&M Univ., 1968. Food and feeding habits of swordfish,Xiphiasgladius, 231 p. in the western North Atlantic. J. Fish. Res. Board Can. Wolff, G.A., and J. H. Wormuth. 25:903-919. 1979. Biornnetric separation of the beaks of two morpho- 1974. Food and feeding habits of swordfish, Xiphias gladius logically similar species of the squid family Omma- T iE +h, ~~~th...,,+ ti,...+;^ nnnn, ;....,.-., .l.b b,LwGuu z.bLaLlblL vLca,,. In X. S. utrephillae. BU!!. Mar. Sci. 29:507-592. Shomura, and R. Williams íeds.1, Proceedings of the inter- Zariquiey-Alvarez, R. national billfish symposium, Kailua-Kona, Hawaii, 9-2Au- 1968. Crustáceos Decapodos Ibéricos. Investigación gust 1972. Part 2: Review and contributed papers. U.S. Pesquera 32:l-510. Dep. Commer., NOAATech. Rep. NMFS SSRF-675:138-141. Zuev, G. V., Ch. M. Nigmatullin, and V. N. Nikolsky. Stillwell, C; E., and N. E; Kohler. 198.5; Nektefiic nceanic qi~i&(geni~s Sthenitezthici Mn3- 1985. Food and feeding ecology of the swordfish Xiphias cow: Agropromizdat [in Russian, Eng. contentsl.

n Appendix file) and narrow (ilj=2.8, where i is the LRL and j is n

the distance between the jaw angles). There is no 3 O Description of the "unknown A lower beak hook in the rostral edge, but rather this is sharp- edged and thickened. The crest is short and has a Terms and measurement used to describe the char- notch in the lateral wall to the side of the crest (Fig. acteristic beak (the 'ZTnknownA) are the same as those 2, A and C).The hood does not lie close to the crest. used by Clarke (1980,1986a). The beak (Fig. 2) belongs The surface of the hood has a very soft fold. The jaw to an unidentified species of oegopsid, and its general angle is obtuse and a sharp anglepoint is present (Fig. shape is similar io ihe beak of Discoieuihis. ii is iaiier 2Ei. jaw angie is obscured from ihe side by a very iow than it is long (Fig. 2A) and although five of them had wing fold (Fig. 2, A, B, and F) which is covered by digested wings, the largest beak (lower rostral cartilage (dotted area). A distinct lateral wall ridge length=4.4mm) had a hU wing with an isolated spot. foms a fin (Fig. 2, E, I),similar 'LO Histioteuthis beaks The restriim is distinctly shnrter than deep (g! !tJype A! described by C!zrke (1980). This mns tnward a=0.67, where g is the hood length in the midline the midpoint of the posterior edge of the lateral wall and a is the length of the rostral edge visible in pro- (Fig. 2, E, 111).The beaks ofDiscoteuthis lack this ridge.