Fish belonging to the genus Cyclothone are believed to be, by number, the most common fish in oceans around the world. Despite their diminutive size of around 2.5 to 3 inches in length, members of this genus are believed to outweigh any other type of fish in terms of biomass.

In addition to their large numbers, Cyclothone has more identified species than any other vertebrate genus. Members of Cyclothone are also known as "Minnows of the Deep;" this is due to their similarity in appearance and the depth at which they are found, which is approximately 1,000 feet below the surface. These fish are further characterized by their bristled mouths and their bioluminescence.