Fish
Bristlemouth
Gonostomatidae · also called bristlemouths
Rarely longer than a finger yet possibly outnumbering every other vertebrate on Earth combined, a bristlemouth drifts through the mesopelagic zone in numbers estimated in the hundreds of trillions, its small photophores erasing its outline from predators above.
Overview
The bristlemouth, family Gonostomatidae, is a tiny, extraordinarily abundant fish native to mesopelagic ocean habitat spanning every major ocean basin in the world. Its likely status as the most numerous vertebrate on the planet, bristle-like teeth, and daily vertical migration make it one of the most ecologically significant, if overlooked, fish groups found anywhere in the ocean.
Abundance hiding in plain sight
Despite its almost unimaginable total numbers, the bristlemouth remains one of the least recognised fish in the world, its small size and deep, dark habitat keeping it entirely out of view for nearly everyone except the researchers who study the deep sea directly.
Status
Least Concern, remaining extremely abundant across mesopelagic ocean habitat worldwide with no known population concerns.
Bristlemouth: common questions
Is the bristlemouth really the most numerous vertebrate on Earth?
Many researchers consider this family to be the most abundant vertebrate group on the planet by individual count, with population estimates reaching the hundreds of trillions across the world's oceans, though the exact total remains difficult to verify precisely.
Why is it called the bristlemouth?
This family has small, sharp, bristle-like teeth lining its jaws, a distinctive feature that gives the group its common name despite the fish's otherwise unremarkable small size.
How does the bristlemouth avoid predators despite being so small?
This family has rows of small light-producing photophores along its underside, used for counter-illumination camouflage that matches the faint light filtering down from the surface, helping erase its silhouette from predators looking upward.
Does the bristlemouth stay at the same depth all the time?
No, this family undertakes daily vertical migration, rising toward shallower water at night to feed on zooplankton before descending back to greater depths by dawn.