The Atlantic bluefin tuna (Thunnus thynnus) is a species of tuna in the Scombridae family. It is variously known as the northern bluefin tuna (mainly when including Pacific bluefin as a subspecies), giant bluefin tuna (for individuals exceeding 150 kilograms or around 330 pounds) and formerly as the tunny.
Atlantic bluefin are native to both the western and eastern Atlantic Ocean, as well as the Mediterranean Sea. Atlantic bluefin have become extinct in the Black Sea. The Atlantic bluefin tuna is a close relative of the other two bluefin tuna species—the Pacific bluefin tuna and the southern bluefin tuna.
Atlantic bluefin tuna may exceed 450 kilograms (990 lb) in weight, and rival the black marlin, blue marlin and swordfish as the largest Perciformes. Throughout recorded history, the Atlantic bluefin tuna has been highly prized as a food fish. Besides their commercial value as food, the great size, speed, and power they display as apex predators has attracted the admiration of fishermen, writers, and scientists.
The Atlantic bluefin tuna has been the foundation of one of the world's most lucrative commercial fisheries. Medium-sized and large individuals are heavily targeted for the Japanese raw fish market, where all bluefin species are highly prized for sushi and sashimi.
Most Bluefin are captured commercially by professional fishermen using longlines; purse seines, assorted hook-and-line gear, heavy rod and reels, and harpoon. Recreationally, bluefin has been one of the most important big-game species sought by sports fishermen since the 1930s, particularly in the United States but also in Canada, Spain, France and Italy.
The Atlantic bluefin tuna is most closely related to the Pacific bluefin tuna (Thunnus orientalis) and the southern bluefin tuna (Thunnus maccoyii), and more distantly to the other large tunas of the genus Thunnus – the bigeye tuna (Thunnus obesus) and the yellowfin tuna (Thunnus albacares). For many years the Pacific and Atlantic bluefin tuna species were considered to be the same, or subspecies, and referred to as the "northern bluefin tuna". This name occasionally gives rise to some confusion as the longtail tuna (Thunnus tonggol) can in Australia sometimes be known under the name "northern bluefin tuna".This is also true in New Zealand and Fiji.
Bluefin tuna were often referred to as the common tunny, especially in the UK, Australia and New Zealand. The name tuna, a derivative of the Spanish atún, was widely adopted in California in the early 1900s and has since become accepted for all tunas, including the bluefin, throughout the English-speaking world. In some languages the red color of the bluefin's meat is included in its name, as in atún rojo (Spanish) and tonno rosso (Italian), amongst others.
The body of the Atlantic bluefin tuna is rhomboidal in profile and robust. The head is conical and the mouth rather large. The head contains a "pineal window" that allows the fish to navigate over its multiple thousands of mile range. The color is dark blue above and gray below with a gold coruscation covering the body and bright yellow caudal finlets. Bluefin tuna can be distinguished from other family members by the relatively short length of their pectoral fins. Their livers have a unique characteristic in that they are covered with blood vessels (striated). In other tunas with short pectoral fins, such vessels are either not present or present in small numbers along the edges.
Fully mature adult specimens average 2–2.5 m (6.6–8.2 ft) long and weigh around 225–250 kg (500–550 lb). The species can reach a maximum length of almost 4.6 m (15 ft). The largest recorded specimen taken under International Game Fish Association rules was caught off Nova Scotia, an area renowned for huge Atlantic bluefin, and weighed 679 kg (1,500 lb). The longest contest between man and tuna fish occurred near Liverpool, Nova Scotia in 1934, when six men taking turns fought a 361 kg (800 lb) tuna for sixty-two hours. Both the Smithsonian Institute and the National Marine Fish Service in North America have accepted that this species can weigh up to 910 kg (2,000 lb), though further details are lacking.
Atlantic bluefin tuna reach maturity relatively quickly. In a survey that included specimens up to 2.55 m (8.4 ft) in length and 247 kg (540 lb) in weight, none was believed to be older than 15 years. However, very large specimens may be up to 50 years old.
The bluefin possesses enormous muscular strength, which it channels through a pair of tendons to its lunate shaped caudal fin for propulsion. In contrast to many other fish, the body stays rigid while the tail flicks back and forth, increasing stroke efficiency.
Bluefin dive to depths of 1,000 metres (550 fathoms). They can reach speeds of 40 miles per hour (64 km/h).
The Atlantic bluefin tuna typically hunts small fish and invertebrates such as sardines, herring, mackerel, squid and crustaceans.