Tuna
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? Tuna |
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| Thunnus
alalunga Thunnus albacares Thunnus atlanticus Thunnus maccoyii Thunnus obesus Thunnus orientalis Thunnus thynnus Thunnus tonggol |
Tuna are several species of ocean-dwelling fish in the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers and include several species that are warm-blooded. Unlike most ocean fish species, which have white flesh, the flesh of tuna is pink. This is because the tuna's blood has a higher oxygen carrying ability than other fish species. Some of the larger tuna species such as the bluefin tuna can raise their blood temperature above the water temperature with muscular activity. This enables them to live in cooler waters and survive a wider range of circumstances.
Tuna is a popular seafood. Some varieties of tuna, such as the bluefin are endangered due to overfishing, some scientists have speculated that eating habits are dramatically affecting the tuna populations in the atlantic and north western pacific regions. However, in others parts of the world exist well maintained fisheries, where such tuna as the bigeye or yellowfin maintain healthy populations.
Due to their higher position in the food chain and the subsequent accumulation of heavy metals from their diet, mercury levels can be relatively high in some of the larger species of tuna such as Bluefin and Albacore. As a result, in March 2004 the United States FDA issued guidelines recommending pregnant women, nursing mothers and children to limit their intake of tuna and other types of predatory fish [1]. Most canned light tuna is the skipjack of light tuna and is very low in mercury.
It is difficult to keep tuna in a captive environment; Monterey Bay Aquarium is one of the few aquaria in the world that successfully keeps tuna in display.
Types include:
- Bluefin tuna, which can grow to 1,500 lb (680 kg)
- Yellowfin tuna
- Albacore tuna
- Bigeye tuna
- Blackfin tuna
Tuna are a common target for big-game fishing, and are mostly caught on artificial lures.
Top Speed
Tuna have been measured swimming at 77 kilometers per hour.
Tuna Farming
In Australia the southern bluefin tuna is one of two species of bluefin tunas that is kept in tuna farms by former fishermen. Its close relative, the northern bluefin tuna, is being used to develop tuna farming industries in the Mediterranean, North America and Japan.
Other species
Species of several other genera (all in Scombridae) are commonly named "tuna":
- Skipjack tuna Katsuwonus pelamis
- Slender tuna Allothunnus fallai
- Bullet tuna Auxis rochei rochei
- Frigate tuna Auxis thazard thazard
- Kawakawa ( little tuna or mackerel tuna) Euthynnus affinis
- Little tunny ( little tuna) Euthynnus alletteratus
- Butterfly kingfish ( Butterfly tuna) Gasterochisma melampus
- Dogtooth tuna Gymnosarda unicolor
Non-Fish Tuna
Opuntia tuna or prickly pear cactus is a cactus that has colored flowers and sweet edible fruit. The fruit of such a tuna cactus is also referred to as tuna.