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Monday, May 11, 2009
Tuna are several species of ocean-dwelling carnivorous fish in the family Scombridae, mostly in the genus Thunnus. Tunas are very fast swimmers—they have been clocked at 70 km/h (45 mph)—and include several species that are warm-blooded. Unlike most fish species, which have white flesh, tuna have flesh that is pink to dark red. The red coloring comes from tuna muscle tissue's greater quantities of myoglobin, an oxygen-binding molecule. Some of the larger tuna species, such as the bluefin tuna, can raise their blood temperature above that of the water through muscular activity. This ability enables them to live in cooler waters and to survive in a wide range of ocean environments.While the fishing of many stocks of tuna is sustainable, it is widely accepted that bluefin tuna have been severely overfished, with some stocks at risk of collapse. The Eastern Pacific Ocean bigeye is also in need of better management in order to maintain sustainability and, in fact, the world's major tuna canneries involved with the International Seafood Sustainability Foundation (ISSF) have agreed to not source from that stock if meaningful conservation measures are not put in place by September 1, 2009.
Commercial fishing
Tuna is an important commercial fish. Some varieties of tuna, such as the bluefin and bigeye tuna, Thunnus obesus, are threatened by overfishing, which dramatically affects tuna populations in the Atlantic and northwestern Pacific Oceans. Other areas seem to support fairly healthy populations of some of the over 48 different species of tuna —for example, the central and western Pacific skipjack tuna, Katsuwonus pelamis—but there is mounting evidence that overexploitation threatens tuna populations worldwide. The Australian government alleged in 2006 that Japan had illegally overfished southern bluefin by taking 12,000 to 20,000 tonnes per year instead of the their agreed 6,000 tonnes; the value of such overfishing would be as much as USD $2 billion. Such overfishing has resulted in severe damage to stocks. According to the WWF, "Japan's huge appetite for tuna will take the most sought-after stocks to the brink of commercial extinction unless fisheries agree on more rigid quotas".
Increasing quantities of high-grade tuna are entering the market from operations that rear tuna in net pens and feed them a variety of bait fish. In Australia the southern bluefin tuna, Thunnus maccoyii, is one of two species of bluefin tunas that are kept in tuna farms by former fishermen.[4] Its close relative, the northern bluefin tuna, Thunnus thynnus, is being used to develop tuna farming industries in the Mediterranean, North America and Japan.
According to the Foodmarket Exchange, the total tuna catch was 3,605,000 tons in 2000, down about 5.7 percent from 3,823,000 tons in 1999. The main tuna fishing nations are concentrated in Asia, with Japan and Taiwan floating the main fleets. Other important tuna fishing nations in Asia are Indonesia and South Korea. Spain and France are also important tuna fishing countries, with their ships fishing primarily in the Indian Ocean. In southeast Asia, the southern Philippines is an important tuna-producing area, particularly General Santos City and Davao.
Japan remains the main tuna fishing nation fishing in the Pacific. In 2000, total tuna caught by Japanese vessels was 633,000 tons, about 17 percent of the world tuna catch. Taiwan was the second biggest tuna producer at 435,000 tons, or about 12 percent of the world's total catch. Spain supplies most of the yellowfin to European canneries, accounting for 5.9 percent of the total tuna catch, while Ecuador and Mexico dominate the Eastern Pacific Ocean.
Nutrition and health
Canned tuna is a prominent component in many weight trainers' diets, as it is very high in protein and is easily prepared. Tuna is an oily fish, and therefore contains a high amount of Vitamin D. A can of tuna in oil contains about the Adequate Intake (AI) of the US Dietary Reference Intake of vitamin D for infants, children, men, and women aged 19–50 - 200 UI. Canned tuna can also be a good source of omega-3 fatty acids, of which it sometimes contains over 300 mg per serving.
Mercury levels
Due to their high position in the food chain and the subsequent accumulation of heavy metals from their diet, mercury levels can be high in larger species such as bluefin and albacore.
In 2009 a California appeals court upheld a ruling that canned tuna does not need warning labels as the methylmercury found in tuna is naturally occurring.
In March 2004 the United States FDA issued guidelines recommending that pregnant women, nursing mothers, and children limit their intake of tuna and other types of predatory fish.However, in January 2009 the FDA released a draft report that found a greater risk to children whose mothers do not eat fish during pregnancy, concluding, "Benefits tend to increase as both fish consumption and exposure to methylmercury increase. The benefits are the size of a fraction of an IQ point through the 95th percentile of exposure to methylmercury (involving the consumption of 44.2 grams of fish per day), but then increases to the size of about 1.5 IQ points at the 99th percentile of exposure (involving the consumption of about 98 grams of fish per day), and to about the size of three IQ points at the 99.9th percentile of exposure (involving 205.7 grams of fish per day). The Chicago Tribune, cited for its inaccurate reporting on tuna related topics, reported that some canned light tuna such as yellowfin tuna is significantly higher in mercury than skipjack tuna, and caused Consumers Union and other activist groups to advise pregnant women to refrain from consuming canned tuna. This was considered extreme and thus not adopted by leading scientific and governing bodies.
The Eastern little tuna (Euthynnus affinis) has been available for decades as a low-mercury, less expensive canned tuna. However, of the five major species of canned tuna imported by the United States it is the least commercially attractive, primarily due to its dark color and more pronounced 'fishy' flavor. Its use has traditionally been restricted exclusively to institutional (non-retail) commerce.
A January 2008 report conducted by the New York Times has found potentially dangerous levels of mercury in certain varieties of sushi tuna, reporting levels "so high that the Food and Drug Administration could take legal action to remove the fish from the market.
Commercial fishing
Tuna is an important commercial fish. Some varieties of tuna, such as the bluefin and bigeye tuna, Thunnus obesus, are threatened by overfishing, which dramatically affects tuna populations in the Atlantic and northwestern Pacific Oceans. Other areas seem to support fairly healthy populations of some of the over 48 different species of tuna —for example, the central and western Pacific skipjack tuna, Katsuwonus pelamis—but there is mounting evidence that overexploitation threatens tuna populations worldwide. The Australian government alleged in 2006 that Japan had illegally overfished southern bluefin by taking 12,000 to 20,000 tonnes per year instead of the their agreed 6,000 tonnes; the value of such overfishing would be as much as USD $2 billion. Such overfishing has resulted in severe damage to stocks. According to the WWF, "Japan's huge appetite for tuna will take the most sought-after stocks to the brink of commercial extinction unless fisheries agree on more rigid quotas".
Increasing quantities of high-grade tuna are entering the market from operations that rear tuna in net pens and feed them a variety of bait fish. In Australia the southern bluefin tuna, Thunnus maccoyii, is one of two species of bluefin tunas that are kept in tuna farms by former fishermen.[4] Its close relative, the northern bluefin tuna, Thunnus thynnus, is being used to develop tuna farming industries in the Mediterranean, North America and Japan.
According to the Foodmarket Exchange, the total tuna catch was 3,605,000 tons in 2000, down about 5.7 percent from 3,823,000 tons in 1999. The main tuna fishing nations are concentrated in Asia, with Japan and Taiwan floating the main fleets. Other important tuna fishing nations in Asia are Indonesia and South Korea. Spain and France are also important tuna fishing countries, with their ships fishing primarily in the Indian Ocean. In southeast Asia, the southern Philippines is an important tuna-producing area, particularly General Santos City and Davao.
Japan remains the main tuna fishing nation fishing in the Pacific. In 2000, total tuna caught by Japanese vessels was 633,000 tons, about 17 percent of the world tuna catch. Taiwan was the second biggest tuna producer at 435,000 tons, or about 12 percent of the world's total catch. Spain supplies most of the yellowfin to European canneries, accounting for 5.9 percent of the total tuna catch, while Ecuador and Mexico dominate the Eastern Pacific Ocean.
Nutrition and health
Canned tuna is a prominent component in many weight trainers' diets, as it is very high in protein and is easily prepared. Tuna is an oily fish, and therefore contains a high amount of Vitamin D. A can of tuna in oil contains about the Adequate Intake (AI) of the US Dietary Reference Intake of vitamin D for infants, children, men, and women aged 19–50 - 200 UI. Canned tuna can also be a good source of omega-3 fatty acids, of which it sometimes contains over 300 mg per serving.
Mercury levelsDue to their high position in the food chain and the subsequent accumulation of heavy metals from their diet, mercury levels can be high in larger species such as bluefin and albacore.
In 2009 a California appeals court upheld a ruling that canned tuna does not need warning labels as the methylmercury found in tuna is naturally occurring.
In March 2004 the United States FDA issued guidelines recommending that pregnant women, nursing mothers, and children limit their intake of tuna and other types of predatory fish.However, in January 2009 the FDA released a draft report that found a greater risk to children whose mothers do not eat fish during pregnancy, concluding, "Benefits tend to increase as both fish consumption and exposure to methylmercury increase. The benefits are the size of a fraction of an IQ point through the 95th percentile of exposure to methylmercury (involving the consumption of 44.2 grams of fish per day), but then increases to the size of about 1.5 IQ points at the 99th percentile of exposure (involving the consumption of about 98 grams of fish per day), and to about the size of three IQ points at the 99.9th percentile of exposure (involving 205.7 grams of fish per day). The Chicago Tribune, cited for its inaccurate reporting on tuna related topics, reported that some canned light tuna such as yellowfin tuna is significantly higher in mercury than skipjack tuna, and caused Consumers Union and other activist groups to advise pregnant women to refrain from consuming canned tuna. This was considered extreme and thus not adopted by leading scientific and governing bodies.
The Eastern little tuna (Euthynnus affinis) has been available for decades as a low-mercury, less expensive canned tuna. However, of the five major species of canned tuna imported by the United States it is the least commercially attractive, primarily due to its dark color and more pronounced 'fishy' flavor. Its use has traditionally been restricted exclusively to institutional (non-retail) commerce.
A January 2008 report conducted by the New York Times has found potentially dangerous levels of mercury in certain varieties of sushi tuna, reporting levels "so high that the Food and Drug Administration could take legal action to remove the fish from the market.
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