The family Scombridae, the mackerels, tunas, and bonitos, includes some of the world’s most popular food and sport fishes. The family also boasts the fastest-swimming fishes in the world, and bluefin tunas are probably the largest of all bony fishes. Scombrids’ size, speed, and popularity are related to their high degree of adaptation to a pelagic, nomadic existence. Their bodies are formed to maximize swimming efficiency, and tunas even have a vascular heat exchange system that allows for prolonged swimming in colder water (see Physical Description). Smaller mackerels often live closer to shore, but other mackerels, tunas, and bonitos roam deeper waters, often in wide migratory patterns (see Habitat). Due to their great range and extensive use as food fish, scombrids bear many common names and have long been familiar to humans. Bonitos, for example, appear in Captain Cook’s journals. Human influence, however, has rendered at least five species endangered or vulnerable to extinction. The family Scombridae is comprised of two tribes, subdivided into 15 genera and 49 species. (Helfman, Collete, and Facey, 1997; Johnson and Gill, 1998; Nelson, 1994; The World Conservation Union, 2002; Wheeler, 1985)