Yellowfin Tuna, Thunnus albacares

This is a large torpedo-shaped fish, with a round body that is metallic blue-green above and silvery white below, with lots of light vertical lines. It has sturdy fins, and a series of bright yellow finlets between the dorsal and anal fins and the crescent caudal (tail) fin. This migratory fish prefers the warm surface water where the younger ones school in big groups, or just below where they can catch smaller fish under drift wood or seagrass. It is popular with commercial fisheries as it grows larger than 100 inches long, more than 400 pounds, and It is found in oceans worldwide.

Also known as

Allison’s tuna, Pacific long-tailed tuna, yellow finned albacore.

French

Albacore, Grand Fouet, Thon Jaune.

Most large yellowfins have overextended second dorsal and anal fins that may reach more than halfway back to the tail base in some large specimens. In smaller specimens under about 60 lb (27 kg) and in some very large specimens as well, this may not be an accurate distinguishing factor since the fins do not appear to be as long in all specimens. The pectoral fins in adults reach to the origin of the second dorsal fin, but never beyond the second dorsal fin to the finlets as in the albacore. The bigeye tuna (T. obesus) and the blackfin tuna (T. atlanticus) may have pectoral fins similar in length to those of the yellowfin. The yellowfin can be distinguished from the blackfin by the black margins on its finlets. Blackfin tuna, like albacore, have white margins on the finlets. It can be distinguished from the bigeye tuna by the lack of striations on the ventral surface of the liver.

This is probably the most colorful of all the tunas. The back is blue black, fading to silver on the lower flanks and belly. A golden yellow or iridescent blue stripe runs from the eye to the tail, though this is not always prominent. All the fins and finlets are golden yellow though in some very large specimens the elongated dorsal and anal fins may be silver edged with yellow. The finlets have black edges. The belly frequently shows as many as 20 vertical rows of whitish spots.

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.

It is highly esteemed both as a sport fish and as table fare. Its flesh is very light compared to that of other tunas, with the exception of the albacore, which has white meat

Habitat

Yellowfin tuna inhabit the mixed surface layer of the ocean, they mostly range in the top 100 m (330 ft) of the water column and they are capable of diving to considerable depths.It has been recorded as diving down to 1,160 m (3,810 ft).

Although mainly found in offshore waters, yellowfin tuna approach the shore when the right conditions exist. Mid-ocean islands such as the Hawaiian archipelago, island groups in the Western Pacific, Caribbean, and Maldives islands Indian Ocean, as well as the islands of the Atlantic, often harbor yellowfin feeding on the bait fish, close to the shoreline.

Yellowfin tuna sometimes travel in schools with similarly sized companions. They sometimes school with other tuna species and mixed schools of small yellowfin, skipjack tuna. Large yellowfin tunas have also been seen with porpoises or dolphins, particularly the spotted, spinner and common dolphins Shcools of Yellowfin have been observed under drifting flotsam such as logs and pallets.

 Diet and predation

Yellowfin tuna prey include other fish, pelagic crustaceans, and squid. Their body shape is particularly adapted for speed, enabling them to capture fast-moving bait fish such as flying fish, sauries, and mackerel. Schooling species such as myctophids or lanternfish and similar pelagic drift fish, anchovies, and sardines are frequently taken.

Yellowfin are preyed upon when young by other pelagic hunters, including larger tuna, seabirds, and predatory fishes such as wahoo, shark, and billfish. As adults they are threatened only by the largest and fastest hunters, such as toothed whales, killer whale, sharks such as the mako, great white, large Atlantic blue marlin, Pacific blue marlin, and black marlin. The main source of mortality, however, is industrial tuna fisheries or in other words man.

Yellowfins  are warm-blooded, and their warm muscles make them extremely strong swimmers, reaching “speeds of up to 50 miles per hour”.