species of ocean-dwelling fish in the family Scombridae.
Unlike most ocean fish species, which have white flesh,
the flesh of tuna is pink. This is because the tuna's
muscle tissue has a higher oxygen storage capacity than
other fish species.
Tuna is a popular
seafood. Some varieties of tuna, such as the bluefin, are
endangered because of over fishing, while others are part
of well maintained fisheries, such as the bigeye or
yellowfin, and are listed as a "best choice" on
the Monterey Bay Aquarium's Seafood Watch program.
Mercury levels are
oftentimes relatively high in tuna, as they sit fairly
high in the food chain and mercury is not metabolized by
most animals, causing mercury to accumulate in predators.
bluefin, which can
grow to 1,500 lb (680 kg).
bonito, in some
countries ("tuna" designation is disputed)