Taxonomy & naming
Opsariichthys pachycephalus was described by Albert Günther in 1868, with Taiwan as the type locality. The Catalog of Fishes gives Opsariichthys pachycephalus Günther, 1868 as valid in Xenocyprididae. Its range is Taiwan.
Morphology
A stream chub. FishBase gives a maximum of 6.5 in TL for males or unsexed fish. Opsariichthys chubs are generally laterally compressed with a large mouth, and males of the genus develop a hooked lower jaw and bright colouring when breeding.
Habitat
FishBase records the species from Taiwan and classes it as demersal and subtropical. No further habitat details are recorded.
Feeding
Diet is not recorded in the FishBase entry. The genus Opsariichthys is made up of active predators that take insects and small fish.
Mating
Courtship and spawning behaviour are not recorded in the FishBase entry.
Breeding
Fecundity, egg type and spawning season are not recorded in the FishBase entry.
In the aquarium
A fast chub for a large, cool tank with flow. FishBase gives no temperature, pH or hardness range for this species, and the atlas does not set one. Keep it with fish of similar size, since adults are likely to eat small tank mates, and keep the tank covered.
Conservation
No IUCN assessment for this species is known to the atlas.