Thunnus

Thunnus is a genus of ocean-dwelling ray-finned bony fish from the Scombridae (Mackerel) family. More specifically, Thunnus is one of five genera which comprise the Thunnini tribe – a tribe that is collectively (and famously) known as the tunas. Also called the true tunas or real tunas, Thunnus consists of eight species of tuna (more than half of the overall tribe), divided into two subgenera. The word Thunnus is the Middle Latin form of the θύννος – which is in turn derived from θύνω (thynō), "to rush; to dart". The first written use of the word was by Homer.

Their coloring, metallic blue on top and shimmering silver-white on the bottom, helps camouflage them from above and below. They can grow to 15 feet long and weigh over 1,000 pounds, and can swim up to 50 miles per hour when pursuing prey. Atlantic bluefin tunas are warm-blooded, which is a rare trait among fish, and are comfortable in the cold waters. Bluefin fish are found in Newfoundland and Iceland, as well as the tropical waters of the Gulf of Mexico and the Mediterranean Sea, where they go each year to spawn.

Due to overfishing the genus range has been significantly reduced, being effectively removed from the Black Sea, for example.

Taxonomy
This genus has eight species in two subgenera:
 * Subgenus Thunnus (Thunnus):
 * Albacore, T. alalunga (Bonnaterre, 1788).
 * Southern bluefin tuna, T. maccoyii (Castelnau, 1872).
 * Bigeye tuna, T. obesus (Lowe, 1839).
 * Pacific bluefin tuna, T. orientalis (Temminck & Schlegel, 1844).
 * Atlantic bluefin tuna, T. thynnus (Linnaeus, 1758).
 * Subgenus Thunnus (Neothunnus):
 * Yellowfin tuna, T. albacares (Bonnaterre, 1788).
 * Blackfin tuna, T. atlanticus (Lesson, 1831).
 * Longtail tuna, T. tonggol (Bleeker, 1851).





Genus membership
Until recently, it was thought that there were seven Thunnus species, and that Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. In 1999 Collette established that based on both molecular and morphological considerations, they are in fact distinct species.

The genus Thunnus is further classified into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group).


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Overfishing
The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished and bluefin is the most endangered and considered "a serious conservation concern". Complicating the efforts for sustainable management of bluefin fish stocks within national exclusive economic zones (EEZ) is bluefin migrate long distances and hunt in the mid ocean that isn't part of any country's EEZ and therefore have been vulnerable to overfishing by multiple countries' fishing fleets. International agreements and conventions are good faith agreements and are difficult to monitor or enforce. Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese, yields are lower than other farmed fish due to the slow growth rate of Bluefin tuna, therefore keeping prices high. On December 30, 2012, a 489 lb bluefin tuna caught off northeastern Japan, was sold at the Tsukiji fish market in Tokyo for a record 155.4 million yen ($1.76 million) – a unit price of JP¥ 1.274 million/kg (US$ 3,600/lb).