Atlantic Bluefin Tuna

The **Atlantic bluefin tuna** (***Thunnus thynnus***) is a species of tuna in the family Scombridae. It is variously known as the **northern bluefin tuna** (mainly when including Pacific bluefin as a subspecies), **giant bluefin tuna** [for individuals exceeding 150 kg (330 lb)], and formerly as the **tunny**.

Atlantic bluefins are native to both the western and eastern Atlantic Ocean, as well as the Mediterranean Sea. They 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.

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-miles range. Their 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 (496–551 lb), and rival the black marlin, blue marlin, and swordfish as the largest Perciformes. 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 (1,497 lb) and was 3.84 m (12.6 ft) long. The longest contest between man and tuna fish occurred near Liverpool, Nova Scotia in 1934, when six men taking turns fought a 164–363 kilograms (361–800 lb) tuna for 62 hours. Both the Smithsonian Institution and the U. S. National Marine Fisheries Service have accepted that this species can weigh up to 910 kg (2,010 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 (545 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. It also has a very efficient circulatory system. It possesses one of the highest blood-hemoglobin concentrations among fish, which allows it to efficiently deliver oxygen to its tissues; this is combined with an exceptionally thin blood-water barrier to ensure rapid oxygen uptake.

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 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.

This commercial importance has led to severe overfishing. The International Commission for the Conservation of Atlantic Tunas affirmed in October 2009 that Atlantic bluefin tuna stocks had declined dramatically over the last 40 years, by 72% in the Eastern Atlantic, and by 82% in the Western Atlantic. On 16 October 2009, Monaco formally recommended endangered Atlantic bluefin tuna for an Appendix I CITES listing and international trade ban. In early 2010, European officials, led by the French ecology minister, increased pressure to ban the commercial fishing of bluefin tuna internationally. However, a UN proposal to protect the species from international trade was voted down (68 against, 20 for, 30 abstaining). Since then, enforcement of regional fishing quotas has led to some increases in population. As of 4 September 2021 the Atlantic bluefin tuna was moved from the category of Endangered to the category of Least Concern on the IUCN Red List of Threatened Species. However, many regional populations are still severely depleted, including western stocks which spawn in the Gulf of Mexico.

Most bluefins are captured commercially by professional fishermen using longlines, purse seines, assorted hook-and-line gear, heavy rods and reels, and harpoons. Recreationally, bluefins have 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.