Tropical latitudes in the eastern Indian and wider Pacific oceans
Rocky and coral reefs
Order Beryciformes (squirrelfishes and relatives), Family Anomalopidae (flashlightfishes)
The flashlightfish is an interesting species, related to the squirrelfishes, slimeheads, and others. It lives on coral reefs and rocky outcrops throughout the Pacific Ocean and in the eastern Indian Ocean. Flashlightfish get their name from the large light organs present under each eye. It is noted for being one of very few shallow-water species that can produce light.
Flashlightfish are predominately nocturnal and are only rarely observed by SCUBA divers during the day. They spend most of the daylight hours hidden in caves or holes in the reef surface. They feed at night away from the reef surface and likely use their light organs to help them locate small, planktonic prey. Like many species that produce light, the flashlightfish has a muscular skin flap that it can manipulate to reveal or hide its light. In this manner, it likely also uses its light to communicate with others of the same species and to confuse predators. This species’ ability to produce light implies that it is a descendent of a deep-sea lineage. Several of its most closely related groups still inhabit the deep sea (including fangtooths, slimeheads, and others). Though most groups of deep-sea fishes are descendents of shallow water forms, the flashlightfish seems to represent an opposite colonization.
The flashlightfish is likely naturally rare. It is not eaten by people but is occasionally captured for use in public and private aquaria. As an inhabitant of vulnerable Pacific coral reefs, this species’ fate is tied to that of its preferred ecosystem. Destructive fishing, climate change, ocean acidification, pollution, and other problems threaten coral reefs around the world and risk the fishes and invertebrates that rely on them.