Red-tail Black Shark Breeding Guide

Breeding the red-tail black shark (Epalzeorhynchos bicolor): a Critically Endangered cyprinid bred only commercially by hormone induction, impractical at home.

Overview

Epalzeorhynchos bicolor is an egg-laying cyprinid that is listed as Critically Endangered on the IUCN Red List (2011). It was believed extinct in the wild between 1996 and 2011, with a single specimen rediscovered in 2013 along the Mae Khlong River in west Thailand. Virtually all aquarium fish are commercially produced.

Sexing

Sex is difficult to determine until the fish are roughly 15 months old. Females are larger and wider-bodied, while males show brighter coloration, slimmer bodies and a more pointed dorsal fin.

Spawning Behavior & Trigger

Spawning triggers, mating cues and natural behaviour remain poorly understood. The species is a confirmed egg-layer, but on commercial farms reproduction is induced by hormone injection rather than by recreating a natural spawning trigger, and no replicable aquarium spawning method exists for hobbyists.

Common Challenges

Extreme intraspecific aggression prevents keeping more than one individual per tank, removing any chance of natural pairing. Even where hormone-induced spawning succeeds, high post-spawning mortality is reported. The species' conservation status further means that ex-situ breeding is recommended at the program level rather than as a hobby pursuit.