Tuna are several 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 overfishing, 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. Tuna's flavor and texture are preserved when it's seared on the outside but raw on the inside. In fact, beyond medium rare most tuna tastes like cat food. Exception is canned tuna.
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)