Yellowfin Tuna

| By xfernal on 6/25/2014 3:26:01 PM | Views (12262)

Yellowfin is often marketed as ahi, from its Hawaiian name ʻahi although the name ʻahi in Hawaiian also refers to the closely related bigeye tuna. The species name, albacares ("white meat") can lead to confusion. The tuna known as albacore in English, is a different species of tuna: Thunnus alalunga. However, yellowfin tuna is officially designated albacore in French, and is referred to as albacora by Portuguese fishermen.

The yellowfin tuna is one of the largest tuna species, reaching weights of over 300 pounds (140 kg), but is significantly smaller than the Atlantic and Pacific bluefin tunas that can reach over 1,000 pounds (450 kg) and slightly smaller than the bigeye tuna and the southern bluefin tuna. Reported sizes in the literature have ranged as high as 239 centimeters (94 in) in length and 200 kilograms (440 lb) in weight.

The second dorsal fin and the anal fin, as well as the finlets between those fins and the tail, are bright yellow, giving this fish its common name. 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.

Yellowfin tuna are epipelagic fish that inhabit the mixed surface layer of the ocean above the thermocline. Sonic tracking has found that although yellowfin tuna, unlike the related bigeye tuna, mostly range in the top 100 meters (330 ft) of the water column and penetrate the thermocline relatively infrequently, they are capable of diving to considerable depths. An individual tagged in the Indian Ocean with an archival tag spent 85% of its time in depths shallower than 75 meters (246 ft) but was recorded as having made three dives to 578 m, 982 m and 1,160 meters (3,810 ft).

Deeper diving and cruising seems to happen more often in the daytime, changing to shallower swimming at night, probably in response to the vertical movement of prey items in the deep scattering layer. They are normally a schooling fish and stay in their immediate school.

Although mainly found in deep offshore waters, yellowfin tuna may approach shore when suitable conditions exist. Mid-ocean islands such as the Hawaiian archipelago, other island groups in the Western Pacific, Caribbean and Maldives islands Indian Ocean, as well as the volcanic islands of the Atlantic such as Ascension Island often harbor yellowfin feeding on the baitfish these spots concentrate close to the shoreline. Yellowfin may venture well inshore of the continental shelf when water temperature and clarity are suitable and food is abundant.

Yellowfin tuna 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 that some follow moving vessels. Hawaiian yellowfin associate with anchored fish aggregation devices (FADs) and with certain sections of the 50-fathom curve.

Yellowfin tuna prey include other fish, pelagic crustaceans, and squid. Like all tunas their body shape is evolved for speed, enabling them to pursue and capture fast-moving baitfish such as flying fish, saury and mackerel. Schooling species such as myctophids or lanternfish and similar pelagic driftfish, anchovies and sardines are frequently taken. Large yellowfin prey on smaller members of the tuna family such as frigate mackerel and skipjack tuna.

In turn, yellowfin are preyed upon when young by other pelagic hunters, including larger tuna, seabirds and predatory fishes such as wahoo, shark and billfish. As they increase in size and speed, yellowfin become able to escape most of their predators. 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, and large blue marlin and black marlin.

Yellowfin tuna are a popular sport fish in many parts of their range and are prized for their speed and strength when fought on rod and reel. Many anglers believe that large yellowfin are, pound for pound, the fastest and strongest of all big game tunas.

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.

Catch Information

Species:
Yellowfin Tuna

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