BALISTIDAE 



CARANGIDAE 



BRAMIDAE 



CHIASMODONTIDAE 



SYNGNATHIDAE 



PRIACANTHIDAE 



7 TETRAODONTIDAE 



8 HOLOCENTRIDAE 

 ACANTHURIDAE 

 SCOMBRIDAE 



11 CHAETODONT1DAE 



12 LUTJANIDAE 



13 OGCOCEPHALIDAE 



14 GEMPYLIDAE 



15 ALEPISAURIDAE 



16 PARALEPIDIOAE 



17 CORYPHAENIDAE 



18 GAOIOAE 



19 ALL OTHERS 



Percent Frequency of Occurrence 



Figure 2. — Relative importance of families of fishes present in more 

 than 1% of the stomachs of western North Atlantic Thunnus 

 albacares. Percent frequency of occurrence is on the horizontal axis, 

 mean length (mm SL) of forage family on the vertical axis, and mean 

 number of individuals in a forage family on the third axis. The most 

 important families are those that occur more frequently (to the right 

 on the horizontal axis), average larger in size (lines coming up from 

 the horizontal axis), and are the most numerous (displaced back into 

 page on third axis). 



most important forage families in terms of size and fre- 

 quency of occurrence. Gempylids consisted mostly of 

 Diplospinus multistriatus which was present in 36% of 

 the stomachs and was the largest sized group (x 151 mm 

 SL). Paralepididae occurred in 29% of the stomachs and 

 averaged 101 mm SL. Bramidae were present in 64% of 

 the stomachs examined, but were less important in terms 

 of size. Omosudis lowei was also frequently eaten, 

 although the family Omosudidae as a whole did not oc- 

 cur frequently. The only group to occur in large numbers 

 was Ogcocephalidae, 40 of which were present in a single 

 stomach. 



Thunnus thynnus. — The food of T. thynnus included 

 17 families of fishes (Appendix Table 4). Bramidae (38%) 

 were the most frequently occurring, with Collybus 

 drachme and Taractes spp. (both present with 8% fre- 

 quency) being chiefly responsible for the high frequency 

 of the whole family. Balistidae (17%) were also consumed 

 frequently. Alepisaurus sp., Auxis sp., and Hippocampus 

 erectus occurred relatively frequently, though the fre- 

 quencies of their families were not particularly high. 



The size range of forage fishes was 29-230 mm SL. No 

 single family appeared to be unusually large in size, 

 although T. thynnus forage fishes were larger on the 

 average (.r 107 mm SL) than those eaten by either T. 

 albacares (x 45 mm SL) or T. alalunga (x 37 mm SL), 

 while they were smaller than those of T. obesus (x 213 

 mm SL). 



Pseudoscopelus sp., Hippocampus erectus, Cookeolus 

 boops, Sphoeroides sp., and Auxis sp. were of primary 

 importance (Appendix Table 2). The occurrence of 32 

 Cookeolus boops (13-66 mm SL) in 26 stomachs of T. 

 albacares is of interest because only 13 specimens of this 

 species have previously been recorded from the western 

 Atlantic (Anderson et al. 1972). One of these was iden- 

 tified by Caldwell (1962) from the stomach of one of the 

 T. albacares collected during this study. 



Fishes eaten by yellowfin varied in length 11-360 mm 

 SL, x 45 mm SL. Gempylids (x 216 mm), Coryphaena (x 

 141 mm), Alepisaurus (x 120 mm), paralepidids (x 105 

 mm), and scombrids (x 96 mm) were the largest forage 

 fishes. Except for the Scombridae, they were present in 

 only a few stomachs and in small numbers. 

 Ogcocephalidae, although eaten infrequently and among 

 the smallest (x 17 mm SL) forage fishes, was the only 

 family to occur in large numbers (43 in one stomach, 

 average 19). No fishes which were eaten in large 

 numbers, or which were outstanding in size, occurred 

 with greater than 6% frequency, except for the Scom- 

 bridae. 



Thunnus alalunga. — Fishes consumed by T. alalunga 

 belonged to 21 families (Appendix Table 3). They 

 averaged slightly smaller (x 40 mm SL) than fishes eaten 

 by T. albacares. Gempylidae and Paralepididae were the 



Thunnus obesus. — Nine families and six genera of 

 fishes were identified from 14 T. obesus stomachs: 

 Alepisauridae, Balistidae, Belonidae, Bramidae, 

 Caproidae, Melamphaidae, Nemichthyidae, Paralepi- 

 didae, and Trachipteridae. Only two families occurred in 

 more than one stomach: Paralepididae, in three (37% fre- 

 quency), and Alepisauridae, in two (25% frequency). The 

 fishes eaten by T. obesus were on the whole larger than 

 those consumed by the other species of Thunnus. The 

 smallest was 83 mm SL; others ranged up to 340 mm 

 (x 213 mm SL). 



Alepisaurus. — Thirty-eight genera of fishes from 36 

 families were found in the stomach contents of 

 Alepisaurus (Appendix Table 5). The five most common 

 families included most of the largest fishes eaten. 

 Paralepididae (x 124 mm SL) was the most frequently 

 occurring family, present in 53% of the stomachs examin- 

 ed. Several Paralepis coregonoides measured 600-846 

 mm SL. Gempylidae ranked high in both size (x 105 mm 

 SL) and occurrence (27%). Alepisauridae were the 

 largest prey group eaten (x 213 mm SL) and were present 

 in 12% of the stomachs. Sternoptychids were present in 

 27% of the stomachs. They were not outstanding in size 

 but were often consumed in large numbers — as many as 

 54 in one stomach. Bramidae were present in 11% of the 

 stomachs, although they were not important in either 

 size or number. 



