Taxonomy & naming
Hamilton described the species in 1822 as Cyprinus shacra. It is now placed in Opsarius, with the authority in parentheses. The epithet is a vernacular name. Opsarius is a genus of stream-dwelling cyprinids of South and Southeast Asia, formerly included in Barilius, with an elongate body and a wide mouth suited to taking insects at the surface.
Morphology
A slender, silvery stream fish with a wide mouth. FishBase gives a maximum of 5.5 in TL; colour has not been described in the sources the atlas uses.
Habitat
It lives in rivers and streams of the northern Indian foothills, in the Ganges-Brahmaputra drainage, and FishBase gives the range as India, Bangladesh and Nepal. It was collected in a large river with a bed of sand, mud, gravel, pebble, cobble and boulders. FishBase gives a temperature of at least 72 °F and a pH of at least 8.0, with no upper limits.
Feeding
Opsarius are active surface and midwater predators of insects that fall on the water, taking small invertebrates and sometimes small fish. The diet of this species has not been described separately.
Mating
Mating behaviour has not been described.
Breeding
Captive breeding has not been documented.
In the aquarium
Keep it in a long tank with strong flow, high oxygen, cool to moderate temperatures and a tight lid, since these fish jump. Keep a group, and give small live, frozen and floating foods. Care notes come from the genus.
Conservation
The IUCN Red List category is Least Concern, assessed in 2010. Threats have not been described.