On this Wikipedia yellowfin tuna language links are at the top of the page across from the article title. 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.

Reported sizes in the literature have ranged as high as 2. 2012 off Cabo San Lucas, Mexico. Yellowfin tuna are epipelagic fish that inhabit the mixed surface layer of the ocean above the thermocline. Although yellowfin tuna penetrate the thermocline relatively infrequently, they are capable of diving to considerable depths. Although mainly found in deep offshore waters, yellowfin tuna may approach shore when suitable conditions exist. 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. Yellowfin tuna prey include other fish, pelagic crustaceans, and squid. Like all tunas, their body shape is particularly adapted for speed, enabling them to pursue and capture fast-moving baitfish such as flying fish, sauries, and mackerel. 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. Yellowfins are able to escape most predators because of their speed, swimming at up to 20. Unlike most fish, tuna are warm-blooded. The behavior of abruptly diving to deeper levels may be a tactic to escape predators.

In 2010, 558,761 metric tons of yellowfin tuna were caught in the western and central Pacific Ocean. Formerly, much of the commercial catch was made by pole-and-line fishing, using live bait such as anchovy to attract schools of tuna close to the fishing vessel that were then taken with baited jigs on sturdy bamboo or fiberglass poles or on handlines. 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.

Purse seining largely took over commercial tuna fisheries in the 1960s and 1970s. Today, purse seines account for more of the commercial catch than any other method. The purse-seine fishery primarily operates in the Pacific Ocean, in the historic tuna grounds of the San Diego tuna fleet in the eastern Pacific, and in the islands of the western Pacific, where many U. 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. Since the introduction of “dolphin-friendly” labeling, an increasing number of purse seine sets are now made on “free schools” unassociated with dolphins, as well as schools that associate with floating objects—another long-understood association that has grown in importance in tuna fisheries. Most of the commercial catch is canned, but the sashimi marketplace adds significant demand for high-quality fish. This market is primarily supplied by industrial tuna longline vessels. 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. In tropical and warm temperate areas, the more valuable bigeyes are often the main target, but significant effort is also directed towards larger yellowfins.

Bycatch is a major environmental issue in the longline fishery, especially impacting billfish, sea turtles, pelagic sharks, and seabirds. This section possibly contains original research. This section does not cite any sources. Besides the large-scale industrial purse seine and longline fisheries, yellowfin tuna also support smaller-scale artisanal fisheries that have often supplied local domestic markets for generations. Artisanal fisheries now also often fish for the lucrative sashimi market in many locations where international air shipment is possible. 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.