Northern bluefin tuna is found throughout the Atlantic Ocean, as well as in the Mediterranean and Black Seas. It is a warm-blooded fish which can live for up to 40 years, and grow to over 4 metres in length and 600 kg in weight. Typical specimens are around 2.5 metres long and weigh around 350 kg. Like other tunas, bluefin is highly migratory.
Atlantic bluefin tuna is divided by scientists into two stocks, Eastern and Western. Eastern bluefin tuna reach sexual maturity at around four years, and spawn in June. The main fishing season for the Eastern stock corresponds to the spring spawning season, when the fish come to the surface to form shoals, with most of the annual catch in the Mediterranean being taken in as little as six weeks.
Scientists estimate that the size of the Eastern stock of adult bluefin tuna has fallen by 80% since the early 1970s. At the 2006 annual meeting of the International Commission for the Conservation of Atlantic Tunas (ICCAT), a 15-year recovery plan was agreed, based on reduced TAC, a higher minimum landing size, and stricter control and enforcement.
Bluefin tuna are targeted using a wide range of fishing methods, from rod and line and traditional traps, to long-line fishing on the high seas, and the purse seine fishery. The Mediterranean industrial purse seine fishery which grew up in the 1990s now accounts for more than 70% of the annual EU catch. The purse seine fleet is based in a small number of ports in Spain, France and Italy. Tuna caught using this method are usually transferred to cages at sea for fattening, before being sold.