What's the biggest tuna? That claim goes to the Atlantic bluefin (Thunnus thynnus), which can grow to be 1,500 pounds!

Tuna are the predators of the fish world. Large and athletic, with a mouth full of sharp teeth, they are impressive swimmers with large appetites. There are 15 genera and 51 species in the Scombridae, the broader tuna family, which includes the bonitos, Spanish mackerels, and mackerels. However, the eight members of the genus Thunnus are considered the true tunas. Seven of these (plus the related Skipjack, Katsuwonus) are called the principal market species sought after by canners and anglers and auctioned at high prices at fish markets.