The Food of Bluefin Tuna (Thunnus thynnus) in the Western North Atlantic Ocean

The stomach contents of 250 bluefin tuna, Thunnus thynnus, captured in the western North Atlantic from 1965 to 1966 by longline, purse seine, and trolling, were analyzed quantitatively and qualitatively. A large percentage (65%) of stomachs were empty. The food of bluefin tuna consisted of 22 taxa of fish, 10 of mollusks, and 8 of crustaceans. Salps were also present. By volume, fishes accounted for 76.9% of the stomach contents; mollusks, 18.1%; crustaceans, 4.2%; and unidentified invertebrates and salps, 0.7%. All food organisms were pelagic. The data do not show a clear relation between size of tuna and size of food. Differences were marked between composition of forage found in deep-swimming tunas caught by longline and that in tunas caught at the surface by purse seine or trolling.