Tuna, Tuna

Tunas are very fast swimmersthey 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.

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.

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.

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.

In southeast Asia, the southern Philippines is an important tuna-producing area, particularly General Santos City and Davao.

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.

Swimming near dolphins reduces the likelihood of the tuna being attacked by a shark.

As a result of public outcry, methods have been made more "dolphin friendly", now generally involving lines rather than nets. However, there are neither universal independent inspection programs nor verification of "dolphin safeness" to show that dolphins are not harmed during tuna fishing. According to Consumers Union, the resulting lack of accountability means claims that tuna that is "dolphin safe" should be given little credence.

Tuna are typically eviscerated by hand, then pre-cooked for 45 minutes to three hours. The fish are then cleaned and filleted, packaged into cans, and sealed. The second cooking of the tuna meat (called retort cooking) is carried out in the cans, this time for 2 to 4 hours.

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 1950 - 200 UI.

Source: Wikipedia > Tuna