Bluefin Facts

Taxonomy

• The term “Bluefin” refers to three subspecies: the Atlantic, Pacific, and Southern Bluefin. Like other true tunas, this group is contained within the Thunnus genus and is part of the Mackeral family.

Species of Commercial Interest

• The aforementioned Atlantic, Pacific, and Southern populations are designated under the species names Thunnus thynnus, Thunnus orientalis, and Thunnus maccoyii, respectively.

Distribution

• Atlantic and Pacific bluefin are found in the northern waters of their respective oceans, while southern bluefin tuna are found in the southern waters of the Atlantic and Pacific Oceans, as well as in the Indian Ocean. Pacific bluefin tuna are also found in the South Pacific with some genetic leakage into the Atlantic. Atlantic bluefin tuna are found in the South Atlantic and have also been reported in the Indian Ocean.

 

Biology

• Bluefin tuna are highly migratory pelagic predators. Some individuals have been clocked in excess of 30 miles per hour (48 km/h) during 10 to 20 second sprints, enabling them to hunt squid, herring, mackerel, and other prey that slower predators cannot capture. This is due to the fact that tuna are actually warm blooded, capable of maintaining temperatures above their ambient environment. Atlantic, Southern, and Pacific bluefin tuna species exhibit a moderate age at first maturity (with some populations such as the eastern Mediterranean Sea bluefin tuna maturing earlier in response to excessive fishing pressure), and all have moderate life spans. This species of tuna grows large. Atlantic bluefin tuna may exceed 450 kilograms (990 lb) in weight and be as greater than 7 feet long. 
• Information is often lacking with respect to reproduction. All species of Bluefin are broadcast spawners that are thought to return to specific locations annually to breed. Groups of males and females congregate together in large concentrations to spawn, and at such times are highly vulnerable to commercial fishing. Females are capable of producing millions of eggs, and the three species are thought to be fairly fecund.

Sustainability

• IUCN Red List Status:  
1. Atlantic Bluefin Tuna (Thunnus thynnus): Endangered (EN) 
2. Pacific Bluefin Tuna (Thunnus orientalis): Least Concern (LC) 
3. Southern Bluefin Tuna (Thunnus maccoyii): Endangered (EN) 

• MBA Seafood Watch:

• All populations of bluefin tuna are being caught faster than they can reproduce. Bluefin is being further depleted by ranching operations that collect small bluefin and raise them to full size to sell primarily to the sushi market. In addition, Bluefin is caught with a variety of gear, including purse seines and longlines. Longlines are most common and result in large bycatch, including threatened or endangered species such as sea turtles, sharks and seabirds. Since there are no international laws to reduce bycatch, these longline fleets are contributing heavily to the long-term decline of some of these species.

Potential Health Concerns

• Environmental Defense Fund has issued a health advisory for bluefin tuna due to elevated levels of mercury and PCBs.