Tuna, opah, and mackerel sharks are the only species of fish that can maintain a body temperature higher than that of the surrounding water. An active and agile predator, the tuna has a sleek, streamlined body, and is among the fastest-swimming pelagic fish – the yellowfin tuna, for example, is capable of speeds of up to . However, greatly inflated speeds can be found in early scientific reports and still widely reported in the popular literature. Found in warm seas, it is extensively fished commercially, and is popular as a game fish. As a result of overfishing, some tuna species, such as the southern bluefin tuna, are threatened with extinction.