The yellowfin tuna, scientifically known as Thunnus albacares, is a significant species among tuna, predominantly found in the pelagic waters of tropical and subtropical oceans globally. Frequently referred to as ahi, a name derived from the Hawaiian language, the yellowfin tuna shares this designation with the closely related bigeye tuna in the region. The species name, albacares, meaning "white meat," can lead to some confusion; for instance, it is called albacore in French and albacora by Portuguese fishermen, although the English albacore corresponds to a different species, Thunnus alalunga.
Physical Characteristics
Yellowfin tuna ranks among the larger species of tuna, achieving weights exceeding 180 kg (400 lb). This size, however, is modest compared to the Atlantic and Pacific bluefin tunas, which can surpass 450 kg (990 lb), and is slightly smaller than both the bigeye tuna and the southern bluefin tuna. The bright yellow coloration of the second dorsal and anal fins, along with finlets, contributes to its common name. In mature individuals, these fins can extend close to the tail, resembling sickles or scimitars. The pectoral fins are relatively longer than those of the bluefin tuna, albeit shorter than those of the albacore. The body is characterized by a dark metallic blue on the upper side, transitioning to silver on the belly, adorned with approximately 20 vertical lines. Recorded sizes reach up to 2.4 m (7 ft 10 in) in length and 200 kg (440 lb) in weight, with the current all-tackle International Game Fish Association (IGFA) record standing at 193.68 kg (427.0 lb) from a 2012 catch off Cabo San Lucas, 🇲🇽 Mexico.
Habitat and Behavior
Yellowfin tuna are epipelagic, occupying the ocean's mixed surface layer above the thermocline. Although predominantly found within the top 100 m (330 ft) of the water column, their depth varies with diurnal patterns, often remaining shallower at night and diving deeper during the day. Despite infrequent thermocline penetration, yellowfin tuna are capable of descending to substantial depths, as evidenced by tagged specimens recording dives up to 1,592 m (5,223 ft).
While typically dwelling in offshore waters, yellowfin tuna may venture near shores under favorable conditions. Particularly, mid-ocean islands like the Hawaiian archipelago and other island groups can attract yellowfins due to concentrated baitfish. Yellowfin tuna are known to school with other tuna species and associate with marine mammals and drifting objects.
Diet and Predation
The diet of yellowfin tuna consists of other fish, crustaceans, and squid, with their streamlined bodies optimized for speed, allowing the pursuit of fast-moving prey. Larger yellowfins have been observed preying on smaller tuna species. They face predation threats primarily from larger marine predators, such as sharks and marlin.
Commercial Fishing
Modern commercial fisheries primarily employ purse seines and longlines to capture yellowfin tuna. In 2010, the total catch in the western and central 🌊 Pacific Ocean amounted to 558,761 metric tons. The yellowfin tuna's impressive speed, reaching up to 20.8 m/s (47 mph), coupled with its various physiological adaptations, supports both rapid and sustained swimming, reinforcing its status as an accomplished marine predator.
Why it's threatened
Threat classification from the IUCN Red List.
