While bigeye tuna quality is difficult to determine due to subjective criteria, number 2 quality is usually adequate for the U.S. market while Number 1 quality is primarily exported to Japan. Fresh and frozen bigeye is sold to foodservice operators as loins and steaks. Early fall is a good time to buy fresh bigeye tuna, as demand drops and landings are normally still quite good. Frozen bigeye tuna is commonly treated with carbon monoxide or tasteless smoke to prevent the red color of the fish from going brown. If abused, carbon monoxide can be used to enhance the color of lower grade bigeye. However, fresh bigeye loins and steaks are rarely treated with carbon monoxide to maintain color. Additionally, the quality of pole and handline-caught bigeye can suffer because the fish can "burn" themselves when they struggle as they are landed and will result in the fish having a very short shelf life.
Bigeye tuna, also called ahi, reproduces quickly. Fast and highly migratory, bigeye tuna can be found in the Pacific, Atlantic and Indian Oceans. This tuna is also long-lived but growth rates vary by population and ocean. Seafood Watch reports that in the Indian Ocean bigeye populations are healthy and fishing mortality rates are low. In the Atlantic, bigeye tuna populations are fluctuating around healthy levels, but have been below these levels in recent years, according to a Seafood Watch report. Despite their wide distribution and abundance, bigeye tuna in the Pacific declined over the past several decades due to intense fishing pressure. Bigeye are overfished in the eastern Pacific. In the western and central Pacific, bigeye populations are not healthy and fishing pressure is too high.
Habitat impacts (Wild)
Bigeye tuna are caught primarily with longlines, which are set off the bottom so they have minimal habitat impacts. Bigeye are also caught with troll lines, pole-and-lines, gillnets and purse seines. Purse seines usually have little contact with the bottom, although fish aggregating devices can be anchored there. Trolling and pole-and-line fishing also have minimal impact on bottom habitats, according to the Seafood Watch.
The longlines and purse seines targeting bigeye tuna also capture non-targeted fish such as other tunas, billfish and bony fish as well as sharks, seabirds and threatened sea turtles. Longliners in particular result in high bycatch rates. Purse seiners using fish aggregating devices can inadvertently attract non-targeted fish and sometimes protected species. Juvenile and small adult bigeye tuna bycatch is high for the skipjack and yellowfin purse seine fisheries. Bigeye tuna caught by troll or pole-and-line, particularly in the U.S. Atlantic, results in some of the least bycatch.
Bigeye tuna’s wide distribution requires effective international management, which has not been successful so far. Despite measures that include reporting requirements, observer programs, bycatch reduction, vessel monitoring, and fishing capacity limits, conservation goals are not being met in every region.
In the Atlantic, bigeye tuna is managed by International Commission for the Conservation of Atlantic Tunas (ICCAT). The National Marine Fisheries Service, and Fisheries and Oceans Canada manage tuna in U.S. and Canadian waters. The Inter-American Tropical Tuna Commission manages bigeye and other tuna species in the eastern Pacific.
There is a multi-annual management plan in place for bigeye in the eastern Pacific. However, many of ICCAT’s measures for the longline tuna fisheries do not meet best practice requirements, and scientific advice has not always been followed when setting those measures, according to Seafood Watch. Purse seines have 100% observer coverage but there are no harvest control rules or target reference points. For state waters in the western and central Pacific, the state of Hawaii manages tuna. In U.S. federal waters, the Western Pacific Regional Fishery Management Council (WPRFMC) manages them. Seafood Watch considers measures in this region to be moderately effective. The Western and Central Pacific Fisheries Commission (WCPFC) also manages bigeye. While some purse seine specific management measures have been introduced in that region, the success is not known.
Indian Ocean bigeye tuna are managed by the Indian Ocean Tuna Commission, and by the Ministry of Fisheries and Aquatic Sciences in Sri Lanka. Seafood Watch gave management in that region a red rating.