The Tuna (Thunnidae) are a family of large, swift swimming, predatory oceanic fish. Members of the family are found in all the warmer seas of the world. Tuna typically swim in huge schools and undergo long circular migrations, swimming at up to 50 mph.
Types of tuna include the small Skipjack, the large and valuable Yellowfin, and the enormous Bluefin, which may be twelve feet, or even longer.
Tuna is a valuable and nutritious food fish. It is fished commercially worldwide, especially by the Japanese, both with lines and nets (in which dolphins are often caught simultaneously, since dolphins often swim in company with tuna; this is why tuna are often described as dolphin-friendly), unscrupulous fishermen sometimes deliberately net the dolphins to catch the tuna.
Fresh fish command a high price, and canned tuna is widely available. However the very largest tuna may be dangerous to eat as they can accumulate mercury in their body tissues to potentially hazardous levels.
Tuna is also an important sport fish.