Lanternfish are small, deep-sea fish that belong to the family Myctophidae. There are many genera of lanternfish, with hundreds of species between them. In general, their bodies are slender with silvery scales and large eyes. All but one species of fish in the Myctophidae family have light-producing organs called photophores, hence the common name lanternfish. These organs emit a weak blue, yellow, or green light that is assumed to be used to communicate. Lanternfish are extremely important to the ecosystem of the ocean, with whales, dolphins, and sharks preying heavily upon them.
While the scales of lanternfish are generally silver, the fish can be tinted other colors, such as blue, green, or black. Light-colored species are typically found nearer to the surface, while brown or black fish are located deeper in the ocean. The length of the fish also varies, but they are normally somewhere between 0.8 inches and 1 foot (2 to 30 cm) long. Photophores, the light-producing organs the fish are known for, grow from various places depending on the species, but they are normally on the head or body rather than the fins or other areas.
Myctophidae fish in general are found in ocean waters all over the world, including the South Pacific, South Atlantic, and Indian Oceans. They are in abundance in most places, unlike their relatives in the family Neoscopelidae. The fish belonging to Neoscopelidae are only found in tropical and subtropical waters, and they are similar in appearance to the fish in Myctophidae. In fact, a particular species of the Neoscopelidae family, Neoscopelus macrolepidotus, even shares the common name, lanternfish.
These fish are some of many that create the deep scattering layer, also known as the false bottom, which refers to a layer of live fish in the ocean. This layer was discovered using sonar technology. In the past, it was often mistaken for the ocean floor, but researchers became confused when the supposed ocean floor rose toward the surface somewhat in the evening, and sunk again once morning approached. Eventually, it was theorized and confirmed that the false bottom consists of marine animals.
Even though lanternfish are hardly rare, little is known about many species. This is primarily because they are deep-sea fish that were not discovered until the mid 1800s, at the earliest. Some species were not discovered until the 1950s, and researchers are still gathering information on their migration and behavior patterns, as well as how they communicate.