Angler fish, the common name for an order of marine fish, as well as for many species of the order. Angler fish range in length from three inches (7.5 cm) to about four feet (120 cm), depending on the species and sex. They are usually found in temperate and tropical seas at depths of up to 3,300 feet (1,000 m). Most species of angler fish have a fleshy movable structure growing from the top of the head, resembling a fishing pole. The free end of this growth serves as a lure to attract prey. In some species the lure contains luminescent bacteria that help the fish locate prey by illuminating the water.