ABSTRACT 



The stomachs of 1,097 yellowfin tuna (Neothunnus macropterus) were collected 

 in the central Pacific in 1950 and 1951, and their contents analyzed quantitatively. 

 The tuna were captured by trolling, pole-and-line, and longline, came from different 

 habitats — inshore and offshore, surface and subsurface — and were of different size 

 groups. The results show that the yellowfin accepts a great variety of animal food, 

 from plankton to large fish and squid. Of the total volume of food remains, 47 

 percent was fish, 26 percent squid, and 25 percent crustaceans. A total of 38 fish 

 families and 11 major invertebrate groups was represented. 



Composition of the food varied considerably with size of yellowfin and locale of 

 capture, whether surface or subsurface, near shore or offshore. Comparison of the 

 average volumes of stomach contents indicated that yellowfin from offshore areas 

 contained as much food in their stomachs as those captured just off the reef; and 

 those from subsurface levels as much as those from the surface. Feeding took 

 place during daylight hours. 



Yellowfin captured in the zone of high zooplankton abundance near the Equator 

 contained greater amounts of food in their stomachs than those captured at more 

 northerly or southerly latitudes. Since most elements of the pelagic fauna appear 

 to be acceptable as food, distribution and abundance of the yellowfin is probably 

 determined not by the occurrence of any specific food items but rather by the total 

 amount of food organisms present in an area. 



