98 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 3. — Checklist of food organisms found in the stomachs 

 of 1,097 yellowfin tuna captured in the central Pacific, 

 1960 and 1951 — Continued 



Food organisms 



Vertebrata (Pisces)— Con. 



Sphyraenidae (barra- 

 cudas) — 



Polynemidae (tbreadfins) . 



Priacanthidae (big-eyes) . . 



Carangidae (jacks): 



Decapterus sp -. 



Naucraies ductor __. 



Unidentified jacks - 



Bramidae (pomirets): 



Taractes sp 



Collybus drachme . 



Unidentified porufrets.-. 



Coryphaenidae (dolphins) 



Lutianidae (snappers) 



Chaetodontidae (butter- 

 fly-fishes) 



Pomacentridae (demoi- 

 selles) 



Labridae (wrasses) 



C hampsodontidae 



Bleniidae (blennies): 



Petrosciries sp 



Unidentified blennies. . . 



Acanthuridae (surgeon- 

 fishes) 



Gempylidae (snake mack- 

 erels) : 



Gempylus serpens 



Unidentified snake 

 mackerels 



Scombridae (tunas and 

 mackerels) : 

 Katsuiconus pelamis 



(skipjack)... 



Neothunnns macropterus 



(yellowfin) 



Parathunnus sibi (big- 

 eyed tuna) 



Unidentified tunas 



Nomeidae (rudderfishes) - . 



Bothidae (flatfishes) 



Echeneidae (retnoras): 



Femora remora 



Unidentified remoras — 



Balistidae (triggerfisbes): 



Palistes ringens 



Unidentified trigger- 

 fishes 



Monacanthidae (filefishes) . 



Ostraciidae (trunkfishes) : 



Ostracion diapbana 



O. lentiginosus 



Unidentified trunk- 

 fishes 



Tetrodontidae (puffers) : 

 Spbaeroides layocepbalus . 

 Unidentified puffers 



Diodontidae (porcupine- 

 fishes) 



Molidae (headfishes) : 

 Pamania truncata 



Unidentified fish and fish 

 remains — 



Total- 



Num- 

 ber of 

 organ- 

 isms 



1 

 1 

 6 



46 

 3 

 4 



28 



449 



101 



1 



48 



24 



14 

 8 

 2 



29 

 21 



1,067 



322 

 24 



137 

 1 



215 



1 

 2,439 



Stomachs in 

 which occurred 



Num- 

 ber 



1 

 1 

 5 



24 



1 

 4 



16 



150 



21 



1 



15 



91 

 16 



75 



1 



84 



11 



12 



8 

 1 



529 



Percent 



0.1 

 .1 



.5 



2.2 

 .1 

 .4 



1.5 

 13.8 

 1.9 

 .1 

 1.4 



1.2 



.1 

 4.6 



1.5 



.1 



.2 



2.2 



.1 



.1 



1.4 

 .4 



8.3 

 1.5 



6.8 

 .1 



7.7 



1.0 



1.1 



.7 



.1 



48.2 



Aggregate total 

 volume 



Co. 



5.0 

 2.0 



9.0 



4, 395. 

 960.0 

 445.0 



194.5 

 1,756.6 

 171.0 

 205.0 

 46.0 



60.5 



8.5 

 5.0 

 6.0 



29.6 

 12.0 



1,007.2 



9.0 

 534.0 



2, 668. 



820.0 



270.0 



1,093.5 



2.0 



1.0 



123.0 

 31.0 



698.0 

 49.0 



349.5 

 4.0 



223.6 



768.0 

 133.0 



81.0 



520.0 



4, 204. 1 



62, 336. 1 



Per- 

 cent i 



8.4 



1.8 



.9 



.4 

 3.4 

 .3 

 .4 

 .1 



5.1 

 1.6 



.5 

 2.0 



1.3 



.1 



1.6 

 .3 



.2 



1.0 



8.0 



i Given only when 0.1 percent or greater. 



RESULTS 

 FOOD HABITS OF THE YELLOWFIN TUNA 



Detailed data obtained during this study are 

 presented in table 3. This table incorporates the 

 combined data for all stomachs examined and 

 serves as a checklist of the food organisms identi- 

 fied. It is apparent from table 3 and figure 3 that 

 the food of the 1,097 yellowfins sampled was com- 

 posed by volume almost entirely of fish (46.7 



percent), squid (26.2 percent), and crustaceans 

 (24.8 percent). The small remainder consisted of 

 pelagic tunicates (0.6 percent) and molluscs other 

 than squid (1.7 percent). Representatives of 38 

 fish families and 11 major invertebrate groups 

 were found in the stomach contents. Despite 

 the great variety of organisms only a few items 

 were of primary importance in the diet of the 

 yellowfin. Those food elements ranking large in 

 number, volume, and frequenc} 7 of occurrence were 

 crab larvae, stomatopod larvae, squid, pomfrets 

 (Bramidae), and surgeonfish (Acanthuridae). 

 Fishes such as flyingfish (Exocoetidae), mackerel 

 scad (Decapturus sp.), and skipjack (Katsuwonus 

 pelamis) were relatively important in volume 

 because of their large individual size, but ranked 

 low in number and frequency of occurrence, indi- 

 cating that they were only occasionally utilized. 



Figure 3. — The comparative importance of the major 

 food categories for the 1,097 sampled yellowfin (as 

 percent of total volume). 



Size of organisms taken 



More than 75 percent of the stomachs examined 

 contained organisms individually displacing less 

 than 0.5 cc. The regular occurrence of larval 

 and postlarval crustaceans, and the occasional 

 record of small heteropods and pteropods indicate 

 a consistent tendency for the tuna to take organ- 

 isms of very small size. 



