Flashlightfishes Roughies and Squirrelfishes: Beryciformes

Physical characteristics: Splitfin flashlightfish are 4 to 12 inches (10 to 30 centimeters) long. These fish have large eyes with light-producing organs below them. They have two dorsal (DOOR-suhl) fins, which are the fins along the midline of the back. The rear dorsal fin is triangular and much larger than the front one.

Geographic range: Splitfin flashlightfish live in the western part of the Pacific Ocean from the Great Barrier Reef to southern Japan.

Habitat: Splitfin flashlightfish live in reef areas 66 to 1,300 feet (20 to 400 meters) deep. During the day these fish remain hidden from sunlight, either in deep water or in dark caves. In winter, the fish gather in the warm, shallow waters of the Philippines.

Splitfin flashlightfish use their large light organ during feeding, which is done primarily at night. One of these fishes has its light off. (©Fred McConnaughey/Photo Researchers, Inc. Reproduced by permission.)

Diet: Splitfin flashlightfish use their large light organ during feeding, which is done primarily at night. These fish shun even dim light, searching for food before or after the moon has risen and set or on nights of a new moon. Their diet is mainly animal plankton. Plankton are microscopic plants and animals drifting in water.

Behavior and reproduction: Splitfin flashlightfish have a light-producing organ and control it with muscles that rotate the organ either to allow the glowing bacteria to shine forth or to hide the glow from view. The fish use the light to communicate with one another. Splitfin flashlightfish often travel in schools of twenty-four to forty-eight fish. Little is known about the reproduction of these fish except that they probably do not guard eggs.

Splitfin flashlightfish and people: Splitfin flashlightfish are used in the aquarium business. Sometimes they are used for bait.

Conservation status: Splitfin flashlightfish are not threatened or endangered. ∎