Tuna, Bluefin

Scientific name

Thunnus thynnus, Thunnus orientalis, Thunnus maccoyii

Other names

Medditerranean bluefin tuna, Pacific bluefin tuna, Southern bluefin tuna

Fishing method

Purse seine, Longline and Pole-and-line

Area of capture

All regions

SASSI Colour

Red

Summary

Atlantic bluefin (Thunnus thynnus) is a large tuna of the North Atlantic and the Mediterranean that is slow growing and late to mature. The Atlantic bluefin tuna looks almost identical to the Pacific northern bluefin tuna (Thunnus orientalis), and some authorities consider the two a single species. However, recent genetic analysis suggests that the two are best considered separate species. Southern bluefin tuna (Thunnus maccoyii) is another close relative found only in the southern hemisphere. Atlantic bluefin tuna are moderately vulnerable to fishing pressure. The species is of enormous value to the international sashimi market and is subject to heavy and unrelenting fishing pressure. Fishing pressure on eastern Atlantic bluefin is substantially higher than the level that ICCAT considers sustainable. The southern bluefin tuna is in recognized decline throughout its range. In general, for all three species of bluefin, basic biological data such as growth rates, age at maturity, reproductive potential, and age structure of the population, are poorly known.

Three methods supply most of the world´s tuna: purse seine, long-line, and pole and line. As bluefin are a pelagic species, purse seine, longline, and rod and reel gear rarely come in contact with the ocean bottom to cause damage. Bycatch is of moderate concern in the purse seine fisheries. However, details about the composition and amount of bycatch in the Atlantic tuna purse seine fishery are largely unknown, as ICCAT does not compile purse seine bycatch. Longline fisheries are known to take significant bycatch of marine mammals. Japanese longline observer data shows that sharks were the dominant type of bycatch, with very few turtles and birds caught. Sea turtle bycatch in longline fishing is also common. Both the loggerhead and leatherback sea turtles are listed on the IUCN Red List of Threatened species, as being endangered and critically endangered, respectively. Within the pole and line fishery, there is usually very little bycatch, but sharks and seabirds are occasionally captured. These are mostly alive and subsequently released.

Through international cooperation, tunas are managed by three main regional alliances: in the eastern Pacific, the Inter-American Tropical Tuna Commission (IATTC), founded in 1950 by agreement between the U.S., Costa Rica, and other Pacific tuna fishing nations; in the Atlantic Ocean, the International Commission for the Conservation of Atlantic Tunas (ICCAT), founded in 1966 by agreement between the U.S. and other Atlantic fishing nations; and, in the Indian Ocean, the Indian Ocean Tuna Commission, established in 1991 under the framework of the UN FAO.

The Pacific northern bluefin does not yet benefit from any regional management scheme. Each fishing nation is responsible for management of the fishery within its own territorial waters. However, the Inter-American Tropical Tunas Commission (IATTC) monitors the condition of Pacific northern bluefin and reports on this. The International Commission for the Conservation of Atlantic Tunas (ICCAT) manages Atlantic bluefin tuna in international waters. By 1994, regional management initiatives such as their Trilateral Tuna Agreement had evolved into an international forum known as the Committee for the Conservation of Southern Bluefin Tuna, or CCSBT. This body is responsible for management of this species as a whole in the three oceans, conducting research and setting catch quotas. Because the range of the southern bluefin extends to a small area of the south Atlantic (off the coast of South Africa), ICCAT bears an overlapping responsibility for management of southern bluefin in the Atlantic Ocean. Generally, ICCAT applies CCSBT´s management principles to the Atlantic stock. As of 2000, ICCAT had no additional management recommendations for Atlantic southern bluefin tuna. However, enforcing international tuna fishing law remains a challenge, given that boats operate on the high seas, far from easy observation. Some nations do various amounts of at-sea inspection and enforcement using surface vessels, but such coverage is spotty due to the associated expense.

For more information, email us at sassi@wwf.org.za

What can YOU do?

Don't buy or sell bluefin tuna! Rather choose a green-listed species.