A preliminary study on autumn feeding habits of bigeye tuna (Thunnus obesus) in subtropical waters of North Pacific

We analyzed the stomach contents of 146 bigeye tuna (Thunnus obesus) collected in the subtropical waters of the North Pacific (150°W−164°W, 30°N−37°N) from September to December in 2018 by the Chinese Longline Fisheries Observer Programme. A total of 36 bait species belonging to 28 families were identified. Alepisaurus ferox, Eucleoteuthis luminosa, Lestidium prolixum and Diaphus sp. were the dominant baits, whose relative importance index ratios (IRI%) were 25.65%, 14.48%, 7.56% and 6.77%, respectively. The feeding intensity of bigeye tuna reached the maximum value in the range of 100−110 cm fork length and at Stage III of gonadal maturity, while reached the minimum value at Stage V. Moreover, higher feeding intensity was observed at water layer of 150−250 m. The results improve the understanding of the biological characteristics and feeding habits of bigeye tuna, in addition to its important role in the ecosystem and food network structure.