Fisheries and Oceans Canada
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Bigeye Tuna
Bigeye tuna (Thunnus obesus) looks very similar to bluefin tuna, but the pectoral fin of bigeye is longer and its eye is relatively large compared to the size of its head. The estimated maximum length of bigeye is around 250 cm, while the estimated maximum weight is around 330 kg. It has a cigar-shaped body that is dark metallic brownish-blue to dark yellow on the back and whitish grey along the belly, often with a bluish strip along the side.
Bigeye tuna stocks are widely distributed in tropical and sub-tropical waters of the Atlantic, the Pacific and the Indian Ocean. At the northern edge of their range, bigeye is also found in Canadian waters of the Atlantic Ocean along the edge of the Gulf Stream and Georges Bank, the Scotian Shelf and the Grand Banks. While juvenile bigeye are mixed with yellowfin and skipjack schools, adult bigeye swim at greater depth that the other two tunas. Bigeye tuna are not caught by Canadian vessels in the Pacific Ocean.
Management of tuna on the high seas is shared by: the Indian Ocean Tuna Commission, Inter-American Tropical Tuna Commission (IATTC), International Commission for the Conservation of Atlantic Tunas (ICCAT), and Western and Central Pacific Fisheries Commission (WCPFC).
Atlantic Canadian catches of bigeye tuna totalled 111 tonnes in 2009. Managed through the Integrated Fisheries Management Plan for Atlantic Swordfish and Other Tunas, Canada’s bigeye tuna fishery also adheres to ICCAT’s conservation and management measures. This includes participating in ICCAT’s Statistical Document Program to ensure Canada’s bigeye exports are validated.
A new ICCAT scientific assessment for bigeye tuna was conducted in 2006/07. Based on this assessment, scientists have recommended that the total bigeye catch not exceed 85,000 tonnes. They also recommended closures to surface fisheries in the Gulf of Gunea during November and limiting the number of vessels for several ICCAT members. This includes limiting longline vessels in China to 45, Chinese Taipei to 98 and Philippines to 8, and purse seine boats in Panama to 3. There is currently no quota or catch limit set for bigeye tuna.
In June 2009, IATTC members adopted a 3-year resolution for a program on the conservation of tuna in the Eastern Pacific Ocean. This agreement includes a purse-seine closure of 59 to 73 days, a one-month closure period in the Pacific Northwest of the Galapagos Islands to protect juvenile bigeye, and a reduction in longline catches of adult bigeye of up to 9 per cent. These measures will reduce fishing effort by roughly 20 per cent.
Bigeye tuna in the Western and Central Pacific Ocean is an important conservation concern for the WCPFC, of which Canada is a member. Based on scientific advice that bigeye were overfished and that overfishing was occurring, the WCPFC implemented the conservation management measures which called for a 30% reduction in effort fishing mortality from 2001-2004 levels in order to maintain the bigeye tuna stock at a level capable of producing maximum sustainable yield over the long term. A recent analysis of this measure has concluded that it is unlikely to achieve these objectives and the most recent stock assessment from 2009 concludes that even greater reductions in fishing mortality are now required to achieve the goal of producing maximum sustainable yield over the long term.
Global stocks of bigeye tuna stocks are either fully exploited or over-exploited.
Other Links:
2002 Stock assessment of bigeye tuna in the Western and Central Pacific Ocean
Harley, S., S. Hoyle, A. Langley, J. Hampton, and P. Kleiber. 2009. Stock asssessment of bigeye tuna in the western and central Pacific Ocean. WCPFC-SC5-2009/SA-WP-4. Western and Central Pacific Fisheries Commission, Scientific Committee, Fifth Regular Session, 10-21 August 2009, Port Vila, Vanuatu. 98 p.
