Species Profile

Mountain Sucker Pacific populations

Scientific Name: Catostomus platyrhynchus
Taxonomy Group: Fishes
Range: British Columbia
Last COSEWIC Assessment: November 2010
Last COSEWIC Designation: Special Concern
SARA Status: No schedule, No Status

Individuals of this species may be protected under Schedule 1 under another name; for more information see Schedule 1, the A-Z Species List, or if applicable, the Related Species table below.

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Quick Links: | Description | Habitat | Biology | Threats | Protection | Other Protection or Status | National Recovery Program | Documents

Image of Mountain Sucker


The Mountain Sucker (Catostomus platyrhynchus) is a freshwater bottom-dwelling fish belonging to the family Catostomidae. They are identifiable by their elongated, dark green to grey or brown cylindrical body, with the underneath colored pale yellow to white. Blotches of black are often seen on the sides and a straight lateral line (green to black) is also present. During breeding season this line turns red and fleshy bumps on the surface of the body develop, called “nuptial tubercles.” This species’ mouth is large and ventral with a large upper lip and a lower lip shaped like paired wings. Lips are covered in fleshy bumps called papillae. Notches at the corners of the mouth and an incomplete cleft on the lower lip help to distinguish this population from most other catostomids. Mountain Suckers have a dorsal fin, caudal fin, anal fin, and two each of pectoral and pelvic fins. Adult individuals typically range from 127 to 152 mm in length.


Distribution and Population

Three designatable units (DUs; representing discrete and evolutionarily significant units of the species) exist in Canada: Saskatchewan-Nelson River populations and Milk River populations (occurring in Saskatchewan/Alberta), and Pacific populations (occurring in British Columbia). Pacific populations are found in the Similkameen River and its tributaries including the Columbia River system, North Thompson River, lower Fraser River and potentially at the confluence of the Salmo and Pend d’Oreille Rivers. Abundance estimates for Pacific populations are unknown at this time.



Little information is available on Canadian habitat requirements; in many instances therefore, studies from other regions are used as a proxy. Small streams (e.g., 2 – 10m wide and <1 m deep) are preferred over large ones, although they have been found in lakes and large streams on rare occasions. Water clarity (clear to turbid) and elevation (20-800 m) vary greatly across habitats. Fish are typically found along shorelines where cover is more abundant, however larger vegetation, including pondweeds, muskgrass, algae, and cress, is not always present. Studies from Montana show that substrate composition varies widely, but cobbles appear to be the most common type.



Typical food for the Mountain Sucker consists of plankton, small invertebrates, and microscopic organic matter scraped from the surface of rocks. Spawning occurs in late spring/early summer; at such time typically 990 – 3,710 eggs are laid, usually hatching within two weeks. A typical length reached by young of the year is 30 - 64mm.



Threats to Pacific populations include: • water availability, use and climate change; • channelization and siltation; • impoundments and flow regulation; • toxicity (e.g. chemical spills); and • exotic species. The Mountain Sucker’s naturally fragmented distribution renders them more susceptible to cumulative effects from a multitude of threats, rather than one primary threat. Populations of the Similkameen River are likely the most affected by habitat degradation due to development and mining activities.



Federal Protection

In Canada, the species is afforded protection under the Fisheries Act, and is currently under consideration for listing as Special Concern under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available online at www.AquaticSpeciesAtRisk.ca or on the SARA Registry at www.SaraRegistry.gc.ca.

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.


Other Protection or Status

Provincially, the Mountain Sucker is on the Blue List in British Columbia.



PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

5 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Status Report on the Mountain Sucker Catostomus platyrhynchus in Canada (2011)

    The Mountain Sucker, also commonly known as the Northern Mountain Sucker or the Plains Sucker, is a small (usually < 250 mm fork length) bottom-oriented fish of the western mountainous regions and westernmost Great Plains of North America. The Mountain Sucker has a sub-terminal mouth with characteristic “fleshy bumps” (papillae) on the lips. The body is elongate, cylindrical and somewhat compressed caudally. Molecular genetic data and the distribution of Mountain Suckers among three National Freshwater Biogeographic Zones (NFBZ) identify three designatable units (DU) in Canada (Saskatchewan-Nelson DU, Missouri DU and Pacific DU).

Response Statements

  • Response Statement - Mountain Sucker, Pacific populations (2011)

    This small freshwater fish has a patchy distribution within the North Thompson, lower Fraser and Similkameen rivers drainages in British Columbia. It has a small area of occupancy and number of locations within each of these areas. It is likely that habitat quality will continue to decline over about 40% of its Canadian range owing to increased water extraction in the Similkameen River drainage that climate change is expected to exacerbate.


  • Order Acknowledging Receipt of the Assessments Done Pursuant to Subsection 23(1) of the Act (2016)

    His Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, acknowledges receipt, on the making of this Order, of the assessments done pursuant to subsection 23(1) of the Species at Risk Act by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) with respect to the species set out in the annexed schedule.
  • Order Amending Schedule 1 to the Species at Risk Act (2016)

    The Minister of Fisheries and Oceans has prepared listing advice for the 15 aquatic species received by the GIC. This advice serves as the basis for the Minister of the Environment’s listing recommendations to the GIC. Thirteen of the fifteen species are addressed in the proposed Order Amending Schedule 1 of SARA.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2010 - 2011 (2011)

    Under Canada’s Species at Risk Act (SARA), the foremost function of COSEWIC is to “assess the status of each wildlife species considered by COSEWIC to be at risk and, as part of the assessment, identify existing and potential threats to the species”. COSEWIC held two Wildlife Species Assessment Meetings during the past year assessing the status or reviewing the classification of a total of 92 wildlife species.