Western Atlantic Bluefin Tuna (Thunnus thynnus), also known as Tuna, Bluefin Tuna, Toro, Maguro, Giant Bluefin, Northern Bluefin Tuna; weight – 900 kg (2,000 lb); length – up to 3.9 m (13 ft); lifespan – up to 20 years or more. They have dark blue-black on the back and white on the lower sides and belly. They are the largest of the tuna species. Bluefin Tuna are top predators. Juveniles eat fish, squid, and crustaceans, and adults feed mainly on baitfish such as herring, bluefish, and mackerel. Image courtesy of NOAA.