Bluefin and yellowfin TUNA are two species of fish that belong to the family Thunnidae. They are both large, predatory fish that inhabit the open ocean and are highly sought after for their meat. Bluefin TUNA are the largest of the TUNA species and can grow up to 10 feet in length and weigh up to 1, 500 pounds. Yellowfin TUNA are smaller than bluefin, growing up to 6 feet in length and weighing up to 200 pounds. Both species are popular for commercial and recreational fishing, and are prized for their flavor and texture.