Tan Bristlemouth

Ocean Fishes

Tan Bristlemouth

Cyclothone pallida

Tan Bristlemouth


Worldwide in tropical to temperate latitudes


Deep sea/open ocean (mesopelagic to bathypelagic)

Feeding Habits

Predator (likely)

Conservation Status



Order Stomiiformes (dragonfishes and relatives), Family Gonostomatidae (bristlemouths)


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The tan bristlemouth is a small deep-sea fish that lives in the mesopelagic zone of the open ocean. Together, the bristlemouth fishes in the genus Cyclothone are considered by scientists to be the most abundant vertebrates on Earth. Though they are extremely abundant, they live in a difficult environment to study and are particularly fragile when captured in deep-sea nets, so there is relatively little information known about their biology and ecology.

The tan bristlemouth is small-bodied, reaching lengths of only a few inches and weights of only a few grams. It has a relatively large mouth, compared to its body size and is likely predatory. Being numerically successful in the deep water column, this species one of the most abundant on Earth, and is probably an important prey species for many deep-sea predators. Tan bristlemouths are covered with rows of special light-producing cells that they likely use both for communication with members of their own species and to confuse predators. Breaking up the outline of their silhouette is an important strategy of avoiding predation in the deep sea.

Specific reproductive behaviors are unknown, but this species has separate sexes and reproduces externally (i.e., females release their eggs and males release their sperm into the water column at the same time). Though they may appear tan in coloration at the surface, tan bristlemouths appear to be black in their preferred depth range. This species has only been studied by scientists using nets to collect specimens from the deep sea. Unfortunately, collected specimens do not survive, so it has been impossible to study their behaviors in life. In fact, they are small and fragile enough that specimens are often damaged in the nets, making this species even more difficult to study.

Tan bristlemouths are not eaten by people, and there is no evidence to suggest that people have any negative affects on their populations. This species has not been evaluated by conservation scientists, but given that it is one of the most abundant species in the largest environment on Earth, it is certainly a species of least concern.


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Additional Resources:

IUCN Red List


the Full Creature Index