Fish
Redtail Shark
Epalzeorhynchos bicolor · also called red-tailed black shark
Believed gone from the wild entirely for decades, a redtail shark survived only in aquariums around the world until a small wild population was finally rediscovered in a single Thai river basin, one of the more remarkable near-extinction stories among popular aquarium fish.
Overview
The redtail shark, Epalzeorhynchos bicolor, is native to the Chao Phraya river basin of central Thailand. Its striking black body and red tail, long presumed extinction in the wild, and eventual rediscovery make it one of the most conservation-significant fish commonly kept in home aquariums.
Saved by an aquarium population, almost
For decades, the redtail shark’s survival rested entirely on captive aquarium populations after its wild habitat was destroyed and polluted, a rare case where the pet trade accidentally preserved a species whose natural population had all but vanished.
Status
Critically Endangered, with an extremely limited wild population rediscovered after decades of presumed extinction in its native Thailand habitat.
Redtail Shark: common questions
Was the redtail shark really thought to be extinct?
Yes, for decades it was believed to have disappeared entirely from its natural habitat in Thailand due to habitat destruction and pollution, with aquarium populations around the world representing the only known individuals of the species, before a small wild population was eventually rediscovered.
Is the redtail shark a true shark?
No, despite the name and its shark-like fin shape, it is a freshwater minnow, unrelated to true sharks beyond a superficial resemblance in body outline.
How can you tell a redtail shark from a rainbow shark?
The redtail shark has a solid black body contrasted with a bright red tail, while the closely related rainbow shark shows red or orange across multiple fins rather than just the tail, against a dark body.
Why is the redtail shark still so endangered despite being common in aquariums?
Its wild population remains extremely limited even after rediscovery, confined to a single river basin in Thailand that continues to face habitat pressure, while the species' abundance in captivity has done little to restore its presence in the wild.