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, such
as the bluefin, are endangered due to overfishing,
while others are parts of well maintained fisheries,
such as the bigeye or yellowfin.
Mercury levels are often relatively high in tuna,
due to their higher position in the food chain and
the subsequent accumulation of heavy metals from
their diet. 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.
It is difficult to keep tuna in a captive environment;
Monterey Bay Aquarium is one of the few aquariums
in the world that successfully keep tuna in display.
* Bluefin tuna, which can grow to 1,500 lb (680
* Yellowfin tuna
* Albacore tuna
* Bigeye tuna
* Blackfin tunaTuna are a common target for big
game fishing , and are mostly caught on artificial
Species of several other genera (all in Scombridae)
are commonly named "tuna":
* Skipjack tuna Katsuwonus pelamis
* Kawakawa (little tuna or mackerel tuna) Euthynnus
* Little tunny (little tuna) Euthynnus alletteratus
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