Several different species are commonly known as bluefin tuna, including Atlantic bluefin (Thunnus thynnus), Pacific bluefin (Thunnus orientalis) and Southern bluefin (Thunnus maccoyii).
Kuromaguro, atun de aleta azul, hon maguro, toro (tuna belly)
Bluefin tuna populations are fished more rapidly than they can reproduce and stocks are at record low levels, having never recovered from intensive fishing in the 1970s and 80s. The International Union for the Conservation of Nature (IUCN) has classified the Western Atlantic’s stock of Atlantic bluefin tuna as “Critically Endangered” on its Red List of Threatened Species. International attempts to limit fishing have been ineffective and have not helped stocks regenerate.
Bluefin tuna is highly prized for sushi and sashimi and tuna fishing is highly profitable. The majority of the global catch passes through Japan, where a single fish can sell for up to $100,000, making it one of the most expensive foods in the world.
All bluefin tuna species grow very slowly and reach reproductive maturity at a late age. They are often caught before they have reproduced. Intensive fishing of the youngest fish is particularly worrying, because it prevents the stocks from regenerating. Its commercial value, along with the tendency of some varieties to gather in specific areas to spawn and fertilize their eggs, makes bluefin tuna particularly vulnerable to fishing, both commercial and illegal (pirate fishing of bluefin tuna is widespread).
In March 2010, the member countries of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) refused an EU-supported proposal made by Monaco to ban the international trade in Atlantic bluefin tuna until the species has had a chance to reproduce.
Wild tuna are caught in many different ways, sometimes using purse seines or longlines. Purse seines, which encircle a shoal of fish with a large net before pursing the bottom of the net so that the fish cannot escape, are not very selective and can produce significant bycatch.
A longline is a long fishing line with many shorter lines and hooks attached to it, which hold the bait. Bycatch is a big problem for longline fishing, because the hooks often accidentally capture threatened or endangered species such as sharks, turtles and sea birds.
Many scientific sources have shown that the dramatic drop in bluefin tuna populations in the Mediterranean is one of the factors -along with rising water temperatures- contributing to the proliferation of jellyfish, as bluefin tuna are one of their main predators.
Young tuna are often caught in the wild to be fattened in open-net pens. Aquaculture does not reduce pressure on wild populations, not least because the large quantities of fish needed to feed farmed tuna puts other species at risk. Tuna ranching is practiced mainly in Australia, Croatia, Spain, Malta and Turkey.
Like all the big marine predators, bluefin tuna concentrates residues of mercury and other pollutants such as dioxins and polychlorinated biphenyls (PCBs) in its flesh.
Advice and alternatives
Avoid bluefin tuna and consult online guides for sustainable alternatives in your region.
Food and Agriculture Organisation (available in six languages)