LANTERN FISH
The lanternfish, also known as Symbolophorus barnardi, is a deep-water fish that gets its name from its ability to produce light. The light is given off by tiny organs known as photophores. A chemical reaction inside the photophore gives off light in a chemical process known as bioluminescence. It is the same process used by fireflies and is similar to the chemical reaction inside the green light sticks that children use on halloween. The photophores are located on the fish's head, underside, and tail. It is believed that these light organs are used to attract other small fish on which the lanternfish feeds. They may also be used to signal other lanternfish during mating.
Lanternfish are found in all of the world oceans at depths ranging from 1,200 to 3,000 feet (about 360 to 900 meters). Most species prefer to remain close to the coast where they are commonly found in large schools near the continental slopes. Different species have been known to separate themselves according to depth. They will form dense layers according to species. It is believed that this behavior is intended to reduce competition between species. These layers contain so many fish and are so dense that they can actually be visible on sonar. They can reflect the sonar beams and give the impression of a false ocean bottom known as a deep-scattering layer. This phenomenon confused oceanographers for many years until the source was finally identified.