TUNA, yellowfln / Thunnus albacares (Bonnaterre, 1788); SCOMBRIDAE FAMILY; also called Allison tuna
Occurs worldwide in deep, warm temperate oceanic waters. R is both pelagic and seasonally migratory, but has been known to come fairly close to shore.
Just as the albacore (Thunnus alalunga) has characteristically overextended pectoral fins, the yellowfin has 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 16 (27 kg) and in some very large specimens as well, this maynot be an accurate distinguishing factor since the fins do not appear to be as long in all specimens. The pectoral fins in adult yellowfin tuna reach to the origin of the second dorsal fm, but never beyond the second dorsal fm to the finlets as in the albacore. The bigeye tuna (T obesus) and the blackfin tuna (T atlanticus) may have pec toral fins similar in length to those of the yefowfin. The yellowfin can be distinguished from the blackfin by the black margins on its inlets. Blackfin tuna, like albacore, have white margins on the fin lets. It can be distinguished from the bigeye tuna by the lack of striations on the ventral surface of the liver. The yellowfin tuna has a total of 25 35 gill rakers on the first arch, and has an air bladder as do all species of Thunnus except the longtail tuna, There is no white, trailing margin on the tail.
The yellowfin 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.
Previously, large yellowfms with long second dorsal and anal fins were called Allison tunas or long finned yellowfin tunas, and the smaller specimens were called short finned yellowfin tunas in the mistaken belief that they were a separate species. It is now the general consensus that there is only one species of yellowfin tuna.
The yellowfin's diet depends largely on local abundance, and includes flying fish and other small fish as well as squid and crus taceans. Fishing methods include trolling with small fish, squid, or other trolled baits including strip baits and artificial lures as well as chumming with five bait fishing.
The yefiowfm 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. Yellowfin tuna are an extremely valuable commercial fish and hundreds of thousands of tons are taken worldwide annually by longliners and purse seiners.