Ahi is among the larger tuna species, ranging as high as 2.4 m (94 in) in length and 200 kg (440 lb) in weight. The name comes from the second dorsal fin and the anal fin, as well as the finlets between those fins and the tail, as they are bright yellow. The main body is a very dark metallic blue, changing to silver on the belly, which has about 20 vertical lines.
Ahi often travel in schools with similarly sized companions. They sometimes school with other tuna species and mixed schools of small yellowfin and skipjack tuna, in particular, are commonplace. They are often associated with various species of dolphins or porpoises, as well as with larger marine creatures such as whales and whale sharks. They also associate with drifting flotsam such as logs and pallets, and sonic tagging indicates some follow moving vessels.
Ahi prey include other fish, pelagic crustaceans, and squid. Like all tunas, their body shape is designed for speed, enabling them to pursue and capture fast-moving baitfish such as flying fish, sauries, and mackerel. Schooling species such as myctophids or lanternfish and similar pelagic driftfish, anchovies, and sardines are frequently taken. Large Ahi pray on smaller members of the tuna family such as frigate mackerel and skipjack tuna.
In turn, Ahi are preyed upon when young by other pelagic hunters, including larger tuna, seabirds, and predatory fishes such as wahoo, shark, and billfish. Adults are threatened only by the largest and fastest hunters, such as toothed whales, particularly the false killer whale, pelagic sharks such as the mako and great white, large Atlantic blue marlin and Pacific blue marlin, and black marlin.
Ahi are able to escape most predators, because unlike most fish, tuna are warm-blooded, and their warm muscles make them extremely strong swimmers, with Ahi reaching "speeds of up to 50 miles per hour". (They can navigate enormous distances, sometimes crossing entire oceans.)
To catch your own!