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Bluefin Tuna
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Bluefin Tuna (East Atlantic and Mediterranean)

The bluefin tuna is a member of the mackerel family (Scombridae). Bluefin tuna is the largest tuna species in the world’s oceans, and they are found throughout the North Atlantic and the Mediterranean Sea. They can reach 3.3 m in length, 725 kg in weight and have a lifespan of about 40 years. 

They are able cross the Atlantic Ocean in 50 days, swim up to 70 km/h, and dive deeper than 1000 meters. Bluefin tuna has from 2013 been observed reappearing and feeding in increasing numbers in Norwegian waters. 
Atlantic bluefin tuna (BFT) have a wide geographical distribution, but mainly live in the temperate pelagic ecosystem of the entire North Atlantic and its adjacent waters, for example the Gulf of Mexico, Gulf of St. Lawrence and the Mediterranean Sea. Archival tagging information confirmed that bluefin tuna can tolerate cold as well as warm water temperatures while maintaining a stable internal body temperature. Bluefin tuna preferentially occupy the surface and subsurface waters of the coastal and open-sea areas. Bluefin tuna are a highly migratory species that seems to display a homing behavior and spawning site fidelity to primary spawning areas in both the Mediterranean Sea and Gulf of Mexico. The reappearance of bluefin tuna in historical fishing areas such as Norway suggest that important changes in the spatial dynamics of bluefin tuna may also have resulted from interactions between biological factors, environmental variations and the reduction in fishing effort.
Tagging studies have demonstrated that this fast-swimming species can travel up to 70 km/h, is able to cross the Atlantic Ocean within 50 days, and dive to depths of more than 1000 m. The front of its body is covered with a hood of fused shells. Its dorsal area is blue-black in color; its sides are a shiny mother-of-pearl color; its belly is white. Eastern Atlantic bluefin tuna spawn during May–June primarily in three locations within the Mediterranean. They reach sexual maturity at around 4 years of age; it then can measure over 1 meter in length. Currently, the SCRS assumes for assessment purpose that eastern Atlantic and Mediterranean bluefin tuna contribute fully to spawning at age 5. Juvenile growth is rapid for a teleost fish and a fish born in June attain a length of about 30–40 cm long and a weight of about 1 kg by October. After one year, fish reach about 4 kg and 60 cm long. At 10 years old, a bluefin tuna is about 200 cm and 170 kg and reaches about 270 cm and 400 kg at 20 years. Bluefin tuna is a long-lived species, with a lifespan of about 40 years, as indicated by radiocarbon deposition and can reach 330 cm (SFL) and weigh up to 725 kg.
Bluefin tuna undergo long-distance feeding migrations in the Mediterranean Sea and Atlantic Ocean. Herring, mackerel, and other schooling fish are important prey species.

The bluefin tuna itself is a very delicious and highly sought-after food fish, and has economic importance throughout in its range of distribution. A single bluefin tuna can be sold for several hundred USD; the world record set in 2012 for a single tuna is an incredible $736,000 USD − sold at Tsukiji fish market in Tokyo.


Facts about Bluefin tuna

Latin name: Thunnus thynnus 
Spawning area: Warm waters (> 24 °C) on specific and limited locations in the Mediterranean around the Balearic Islands, Sicily, Malta, Cyprus, and Libya.
Juvenile feeding area: Mediterranean Sea, coast of Portugal and Bay of Biscay
Adult feeding area: North-Atlantic Ocean, including Norwegian coast and Norwegian Sea
Maximum size: 3.3 m / 725 kg
Life span: 40 years
Diet: Zooplankton and small fish as juveniles; mature fish prey on schooling fish such as mackerel, herring, blue whiting, sand lance and sprat, in addition to squid species.

Status, advice and fisheries

Stock status of East Atlantic and Mediterranean bluefin tuna indicate that there is no overfishing. 

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