It belongs to more than a dozen families and is characterized by large mouth, large eyes, and light emitters in one or more parts of the body. Light emitters are used both to trap prey and to lure mates.
Deep-sea fishes have developed these special habits in the course of evolution in order to adapt to the extremely stressful, extremely cold and dark living conditions. Deep sea fish habitat is the most special in the world. Since the competition in the deep sea is not as intense as in the shore or in the shallow sea, many primitive groups have survived to this day. The most important group of deep-sea fishes are deep-sea fishing, squid and puffer fish. Deep-tailed angling is Ceratioidei, which traps prey by shaking the fins of the fins as bait; Chauliodontidae, which has many clip-like teeth, is a fearful predatory fish. The genus Gonostomatidae is the largest fish in the world.