The diet depends largely on local abundance, and includes flying fish, other small fish, squid and crustaceans. Fishing methods include trolling with small fish, squid, or other trolled baits including strip baits and artificial lures as well as chumming with live bait fishing. Yellowfin tuna are an extremely valuable commercial fish and hundreds of thousands of tons are taken worldwide annually by longliners and purse seiners. Though occasionally caught from an ocean pier, it is basically a deep-water species, inhibiting the surface of the open ocean. Large males have high, vertical forehead, while the female's forehead is rounded.
Males grow larger than females.
There are no spines in any of the fins. The dorsal fin has 55-66 soft rays. The anal fin has 25-31 soft rays. They are extremely fast swimmers and feed extensively on flying fish and squid as well as on other small fish. They have a particular affinity for swimming beneath buoys, seaweed, logs, and floating objects of almost any kind.