About Tuna Edit
Tuna is an important warm-water fatty fish of the genus Thunnus of the family Scombridae; which is usually served as steaks Tuna, sometimes called tuna fish, 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 fish species, which have white flesh, the flesh of tuna is pink to dark red. This is because tuna muscle tissue contains greater quantities of myoglobin, an oxygen-binding molecule, than the muscle tissue of most 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 have two dorsal fins, each of which can be dejected into grooves in the back, and a series of fin lets between the rear dorsal fin and anal fin and the tail. The base of the tail is slender, and the caudal fin strongly divided. Species sizes vary by an order of magnitude, from the twenty cm of the island mackerel to the massive 458 cm.