Deep sea fish is a term for fish that live below the photic zone of the ocean. Examples include the lanternfish, flashlight fish[disambiguation needed], cookiecutter shark, bristlemouths, anglerfish, and viperfish
The fish of the deep sea are among the most strange and elusive creatures on Earth. Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep sea fish have evolved appropriately to the extreme sub-photic region in which they live.
Many deep sea fish are bioluminescent, with extremely large eyes adapted to the dark. Some have long feelers to help them locate prey or attract mates in the pitch black of the deep ocean. The deep sea angler fish in particular has a long fishing-rod-like adaptation protruding from its face, on the end of which is a bioluminescent piece of skin that wriggles like a worm to lure its prey. The lifecycle of deep sea fish can be exclusively deep water although some species are born in shallower water and sink on becoming adults. Most bioluminescent color of their light is blue and some of them will produce red light.