The flashlight fish are a family, the Anomalopidae, of beryciform

Beryciformes

Beryciformes is an order of ray-finned fishes. This is a very poorly understood group of 16 families, 57 genera, and about 219 species. Some people believe that it is probably an artificial assemblage of unrelated taxa that are thrown together for convenience only; there are no convincing...

 fish. There are some unrelated fish with similar features, some of which are also called flashlight fish. Notable among these are the deep sea

Deep sea fish

Deep sea fish is a term for any fish that lives below the photic zone of the ocean. The lanternfish is, by far, the most common deep sea fish. Other deep sea fish include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, and viperfish....

 lanternfish

Lanternfish

Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...

, of the family Myctophidae, of which there are over 200 species.

Flashlight fishes live in tropical waters across the world. Some species move to shallow waters or coral during the night, but otherwise, they are exclusively deep water fish.