Castostomus platyrhynchus

Identification Tips:

• Mouth on bottom of head.
• Mouth has a shallow cleft between the lower lips, a deep notch at each corner, and a hardened sheath on the lower jaw.
• Dorsal fin: 10-12 rays

Conservation Status:

British ColumbiaCanadaNatureserve
COSEWICSpecies at Risk Act
Blue ListSpecial ConcernSpecial ConcernG5, S2S3

Information Source: BC Conservation Data Centre:

Life History:

• A very specialized feeder; scrapes algae and aquatic invertebrates from rocks using its chisel-like lower jaw
• Maximum size approximately 25 cm
• Probably a different species than the Mountain Suckers east of the Rockies.
• Little is known about its biology in B.C.


• Found in various river habitats with rocky bottoms.
• Occasionally in Lakes (outside of BC)


British Columbia
• A scattered distribution; Fraser River between Hope and Chilliwack, North Thompson River near Heffley, Similkameen River near Keremeos, and possibly in Salmo River (Kootenays)

• In the west, from Sacramento River in California north to southern BC
• East of the Rocky Mountains (likely a different species) it occurs from Saskatchewan and Alberta through the Missouri River system

Primary Information Source:
McPhail, J.D. 2007. The Freshwater Fishes of British Columbia. University of Alberta Press. Edmonton, Alberta.