Food of the yellowfin tuna in the central Pacific
Reintjes, J.W.; King, J.E.
U S Fish And Wildlife Serv Fish Bull 54(81): 91-110
The stomachs of 1097 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 habitatsinshore and offshore, surface and subsurface and were of different size groups. The results show that the yellowfin accepts a great var. of animal food, from plankton to large fish and squid. Of the total vol. of food remains, 47 % was fish, 26% squid, and 25% 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 localc of capture, whether surface or subsurface, near shore or offshore. Comparison of the avg. vols. 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 amts. 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, distr. and abundance of the yellowfin is probably detd. not by the occurrence of any specific food items but rather by the total amt. of food organisms present in the area.