Comparative study of food of bigeye and yellowfin tuna in the Central Pacific
King, J.E.; Ikehara, I.I.
U S Fish And Wildlife Ser 7 Fish Bull 57(108): 61-85
1956
Accession: 024363950
Stomachs of 166 bigeye tuna (Parathunnus sibi) and 439 yellowfin tuna (Neothunnus macropterus), captured in the central Pacific by longline fishing, were analyzed quantitatively. Representatives of 48 fish families and 11 invertebrate orders were found among the stomach contents of the yellowfin, as compared with 36 fish families and 9 invertebrate orders for the bigeye. Food items of major importance to both species were pomfret (Collybus drachme), snake mackerel (Gempylus serpens), and squid of the families Ommastrephidae and Loliginidae. Notable differences were the complete lack of stomatopods in the food of bigeye, whereas they were common in yellowfin, and the insignificance of juvenile tunas in the food of bigeye, as compared with their prominence in the food of the yellowfin. In both tunas, the smaller individuals consumed a great-er proportion by volume of crustaceans and fish and a lesser proportion of mollusks than the larger size group. In both tunas there was a tendency for the volume of stomach contents to increase with depth of capture, but there was no marked variation in food composition over the range of depth sampled. In the bigeye the volume of stomach contents varied directly with the longline catch rate, while in the yellowfin there was little change in volume of stomach contents even with a marked change in catch rate. Despite these differences, the foods of yellowfin and bigeye were remarkably similar. When occupying the same general area, the two species were found to have essentially the same feeding habits.