Tuna are predators found in marine habitats. There are 15 species of tuna, ranging in size from 50 cm to 4.6 m and weighing 684 kg (bluefin tuna). Tuna is one of the few species that can maintain a body temperature higher than the water temperature. It is one of the fastest pelagic fish (fish that live in schools in the open sea to medium depths) because of its hydrodynamic body. Tuna weighing from 30 kg to 200 kg and more are found in the Adriatic Sea.