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The yellowfin tuna ( Thunnus albacares) is a species of tuna found in pelagic waters of tropical and subtropical worldwide.
Yellowfin is often marketed as ahi, from the Hawaiian ahi, a name also used there for the closely related bigeye tuna ( Thunnus obesus). The species name, albacares ("white meat") can also lead to confusion: in English, the albacore ( Thunnus alalunga) is a different species, while yellowfin is officially designated albacore in French language and referred to as albacora by Portuguese fishermen.
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. The second dorsal and anal fins can be very long in mature specimens, reaching almost as far back as the tail and giving the appearance of or scimitars. The are also longer than the related bluefin tuna, but not as long as those of the albacore. The main body is a very dark metallic blue, changing to silver on the belly, which has about 20 vertical lines.
Reported sizes in the literature have ranged as high as in length and in weight. The all-tackle International Game Fish Association (IGFA) record for this species stands at for a yellowfin caught in 2012 off Cabo San Lucas, Mexico. The fisherman received a prize of $1 million once the catch was confirmed by the IGFA.
Although yellowfin tuna 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 , but was recorded as having made three dives to , and . The maximum dive depth measured in a second study was .
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 or , as well as with larger marine creatures such as and . They also associate with drifting flotsam such as logs and pallets, and sonic tagging indicates some follow moving vessels. Hawaiian yellowfins associate with anchored fish aggregation devices and with certain sections of the 50-fathom curve.
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. Adults are threatened only by the largest and fastest hunters, such as , particularly the false killer whale, pelagic sharks such as the Isurus and great white, large Atlantic blue marlin and Pacific blue marlin, and black marlin. The main source of mortality, however, is industrial tuna fisheries.
Yellowfins are able to escape most predators because of their speed, swimming at up to . Unlike most fish, tuna are warm-blooded. Their unique cardiovascular system, warm body temperature, elevated metabolism and well-developed lymphatic system are all involved in their ability to engage in both rapid bursts and long periods of swimming. When swimming rapidly, a tuna's fins retract into grooves to form a smooth hydrodynamic surface and increase its speed, due to a biological hydraulic system involving the lymphatic system.
The behavior of abruptly diving to deeper levels may be a tactic to escape predators. Evidence from trackers even includes a case in which a diving yellowfin tuna may have been swallowed at a depth of .
Pole-and-line fishing is still carried out today in the Maldives, Ghana, the Canary Islands, Madeira and the Azores. Few pole-and-line boats now specifically target yellowfin, an incidental take compared to the total commercial catch. In the Maldives, the catch is a mix of skipjack tuna and small yellowfins that often associate with them.
Purse-seine vessels locate tuna using onboard lookouts, as was done in the pole-and-line fishery, but they also employ sophisticated onboard electronics, sea-surface temperature and other satellite data, and helicopters overhead. Once a school is located, the net is set around it. A single set may yield . Modern tuna seiners have a capacity up to , reach speeds of over , and carry multiple spotting helicopters.
Purse seining for yellowfin tuna became highly controversial in the late 1970s when it became apparent that the eastern Pacific fishery was killing many , pantropical spotted dolphins and other (often called "" by the tuna fleet) that accompany the fish. This association has been long-recognized by commercial tuna fishermen.
Industrial longlining was primarily perfected by Japanese fishermen who expanded into new grounds in the Western Pacific, Indian and Atlantic Oceans in the late 1950s and early 1960s. Longlining has since been adopted by other fishermen, most notably South Korea, Taiwan and the United States.
Tuna longlining targets larger sashimi-grade fish around and up that swim deeper in the water column. In tropical and warm temperate areas, the more valuable bigeyes are often the main target, but significant effort is also directed towards larger yellowfins. Longlining seeks areas of higher ocean productivity indicated by temperature and chlorophyll fronts formed by upwellings, ocean current eddies and major bathymetry features. Satellite imaging technology is the primary tool for locating these dynamic and constantly changing ocean areas.
Bycatch is a major environmental issue in the longline fishery, especially impacting billfish, sea turtles, pelagic sharks and .
Artisanal fishermen tend to employ assorted hook-and-line gear such as trolling lines, surface and deep handlines and longlines.
By far, the largest fishery using artisanal methods exists in Philippine and Indonesian waters where thousands of fishermen target yellowfin tuna around fish aggregation devices or payaos, although this fishery far exceeds the artisanal scale in terms of tonnage caught and the numbers of participants involved, and should more properly be considered a commercial handline fishery. General Santos is the most important Philippine port for the landing and transhipment of catches. Catches that qualify as sashimi grade are mostly shipped to the Japanese market; those that do not meet the grade are sold locally or canned. Elsewhere in the Pacific, small-boat fishers in Hawaii, Tahiti and other Pacific islands supply local and in some cases foreign markets with fresh yellowfins.
Handline-caught yellowfin tuna is one of the few exports of the economy of St. Helena.
Yellowfin tuna were subsequently discovered by sport fishermen in Bermuda, the Bahamas, Hawaii and many other parts of their range. Larger adult fish which had developed distinctively long sickle fins were initially thought to be a different species and were known as Allison tuna (a name first given by the then curator of the Bermuda Aquarium, Louis Mowbray, in 1920). Such destinations as Hawaii and Bermuda became famed for their catches of these beautiful fish. In Hawaii, various styles of feather lures served as bait, but in Bermuda, chumming techniques from boats anchored on productive banks were evolved to target not only Allison tuna, but also wahoo and the smaller blackfin tuna. Bermudian experts developed techniques to take all these fish on light Fishing tackle, and for many years the International Game Fish Association records for yellowfin tuna were dominated by entries from Bermuda in the lighter line classes, with fish in the and larger class from Hawaii taking most of the heavier line-class records.
Today, yellowfin tuna are a major sport fish pursued by sport fishermen in many parts of the world. Thousands of anglers fish for yellowfin tuna along the eastern seaboard of the United States, particularly in North Carolina and New England. Yellowfin are also a popular gamefish among anglers fishing from U.S. Gulf Coast ports, San Diego and other ports of southern California. Larger "long-range" boats in the San Diego fleet also fish in Mexican waters, searching for yellowfin tuna in many of the grounds that the San Diego pole-and-line tuna clippers used to fish. The yellowfin tuna is also a highly prized catch in the offshore sport fisheries of South Africa, Australia and New Zealand. Sport fishing for yellowfin tuna exists on a smaller scale in many other parts of the world.
Yellowfin tuna are highly sought after for their impressive size and excellent taste, making them a popular target for recreational anglers. The thrill of reeling in a massive yellowfin tuna has attracted many fishing enthusiasts to the Gulf of Mexico, creating a significant source of revenue for local businesses and communities. To ensure the sustainability of yellowfin tuna populations in the Gulf of Mexico, many fishing organizations have implemented catch limits and other measures to protect these fish for future generations of recreational fishermen to enjoy.
Yellowfin buyers recognize two grades, " sashimi grade" and "other", although variation in the quality of "other" grades occurs.
Different seafood sustainability guides come to different conclusions about whether yellowfin fishing is sustainable. The Audubon's Seafood Guide (a guide for what types of marine food products are not ecofriendly) lists troll-caught tuna as "OK", but labels long-line caught as "Be Careful".
Yellowfin is becoming a popular replacement for the severely depleted supplies of southern bluefin tuna.
In 2010, Greenpeace International added the yellowfin tuna to its seafood red list. The Greenpeace International seafood red list is a "list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries".
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