Atlantic Bluefin Tuna – Western Atlantic Population

Thunnus thynnus

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The Atlantic Bluefin Tuna (Thunnus thynnus) is a large, highly migratory, marine fish found across the Atlantic Ocean, Mediterranean and Black Seas. They are managed as two distinct stocks - a western Atlantic population and an eastern Atlantic and Mediterranean population. It has the following features:

  • Streamlined in shape, with two dorsal fins;
  • Dark blue/black in colour with a light blue side and silvery grey underneath;
  • The young grow quite rapidly and reach maturity as early as 4-5 years of age;
  • The general life expectancy is 40 years;
  • Bluefin Tuna can frequently dive to depths of more than 1,000 m;
  • They can grow up to 331 cm long and can weigh up to 725 kg.

Habitat

Atlantic Bluefin Tuna are seasonal migrants to summer feeding grounds in Canadian waters. Bluefin Tuna can tolerate a wide range of temperatures and migrate over long distances.

The western Atlantic Bluefin Tuna population feed during the summer in Atlantic Canadian waters and migrate south during the winter months to the Gulf of Mexico where their spawning, larval and juvenile rearing habitats are located. While their migration patterns are still not clearly resolved in Canadian waters, they can be found over the Scotian Shelf, in the Gulf of St. Lawrence, in the Bay of Fundy, and off of the coast of Newfoundland.

Atlantic Bluefin Tuna juveniles and adults are opportunistic feeders; however, in general, juveniles feed on crustaceans, fish and cephalopods, while adults primarily feed on fish such as herring, anchovy, sand lance, sardine, sprat, bluefish and mackerel.

Threats

In 2011, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed Atlantic Bluefin Tuna as endangered due to a decline of 69% in adult abundance over the past 2.7 generations. The largest threat to Atlantic Bluefin Tuna is considered to be fishing mortality, both targeted and incidental. In Canada, they are harvested commercially from the Scotian Shelf, southern Gulf of St. Lawrence, Bay of Fundy, and the Grand Banks. Pollution is also considered a threat. In particular, there was concern about the potential impact of the Deepwater Horizon oil spill, which occurred in a portion of the primary spawning ground in April 2010. However, there has not been an observed impact on the 2010 year-class as it progresses through the fishery.

The spawning stock biomass (SSB) for the western population of Atlantic Bluefin Tuna declined substantially from the 1970s to 1992. However, following the implementation of a 20 year rebuilding plan in 1998, the SSB has shown signs of improvement. The last two International Commission for the Conservation of Atlantic Tunas (ICCAT) assessments (2012 and 2014) also showed positive signs of the biomass increasing.

Further Information

Atlantic Bluefin Tuna are managed by the ICCAT, of which Canada is a member.  ICCAT is the inter-governmental fishery organization responsible for the conservation of Atlantic Bluefin Tuna and other large pelagic fishes in the Atlantic Ocean and Mediterranean Sea. Atlantic Bluefin Tuna are managed under the Fisheries Act in Canadian waters.

The popularity of Atlantic Bluefin Tuna in highly lucrative markets led to extensive exploitation in several areas. Canada is a strong advocate for conservation using the precautionary approach to stock management. In recent years, Canada played a leading role at ICCAT which resulted in measures to address overexploitation through science-based management, to ensure compliance, and to combat illegal, unreported and unregulated fishing activities.

Atlantic Bluefin Tuna are listed as critically endangered by the International Union for Conservation of Nature.

Visit the Species at Risk (SARA) Public Registry.

Atlantic Bluefin Tuna

Atlantic Bluefin Tuna

Scientific name: Thunnus thynnus
SARA Status: No Status
COSEWIC Status: Endangered
Taxonomy: Fish (marine)
Region: Atlantic Ocean

Atlantic Bluefin Tuna

Photo credit: Fisheries and Oceans Canada

Did You Know?

Most fish breathe by widening their jaws, sucking in water and then squeezing that water past their gills. Bluefin Tuna have a rigid skull and cannot widen their jaws, therefore, they must swim forward with their mouth open, forcing the water into their mouth and past their gills. This means that the tuna must continuously swim so it does not suffocate.

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