Species Profile

Mountain Sucker Milk River populations

Scientific Name: Catostomus platyrhynchus
Taxonomy Group: Fishes
Range: Alberta, Saskatchewan
Last COSEWIC Assessment: November 2010
Last COSEWIC Designation: Threatened
SARA Status: Schedule 1, Threatened

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Quick Links: | Photo | Description | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Mountain Sucker

Mountain Sucker Photo 1



The Mountain Sucker belongs to the family of suckers that live in the western mountainous regions and western-most Great Plains of North America. Based on genetic and geographic factors, the Mountain Sucker has been separated into three Designatable Units in Canada: 1) the Saskatchewan - Nelson River populations; 2) the Milk River populations; and 3) the Pacific populations. The Mountain Sucker has the following characteristics: A sub-terminal mouth, no teeth and fleshy lips (a trait characteristic of suckers); snout is broad and heavy; eyes are small; the body is elongate, cylindrical and somewhat compressed; a relatively small body, with total lengths averaging between 127 to 152 millimeters. The longest length ever recorded was an Alberta specimen at 232 millimeters; the dorsal colouring is typically dark green to grey or brown. The belly is pale yellow to white; there is a dark green to black lateral band and/or five dorsal blotches of fine black pigment on the sides; and during the spawning season, spawning fish develop an orange to red lateral band and both male and females develop “bumps” (tubercles) on their fins.


Distribution and Population

The Mountain Sucker is found only in the western United States and Canada, typically at higher elevations, although they are found in lowland and prairie streams as well. In the U.S., it is found in the Green, upper Columbia, Yakima, upper Sacramento and upper Missouri river systems, as well as the Lahontan and Bonneville Basins, and in tributaries of the Colorado River, as far south as Utah. In Canada, it can be found in the Columbia, Fraser, Saskatchewan and upper Missouri River Systems (Milk River). Although locally abundant in some selected areas, the Mountain Sucker is not abundant in most Canadian waters where they are at the northern extent of their range.



Mountain Suckers are considered a cool water species, and are associated with small streams at elevations between 20 to 800 meters above sea level, although they occur occasionally in lakes, reservoirs and large rivers. Flows are moderate. The materials along the bottoms (substrates) of the water body vary, but are typically characterized by gravel or cobble.



Spawning occurs in late spring or early summer in riffles of moderate to fast flowing water often adjacent to pools. Spawners use the riffle areas, but return to deeper pools once spawning is complete. No nest is built, and the eggs are scattered over river or stream bottoms. Incubation of the eggs is likely between 8 to 14 days, with the frys’ growth rates variable between streams. Females tend to be larger, and live longer than males. Males live about seven years; females live about nine years.



Threats to the Mountain Sucker include habitat loss and degraded habitat quality as a result of agricultural and livestock practices; urbanization and industrial development; water management practices and irrigation; and the introduction of aquatic invasive species. In south-central British Columbia and southern Alberta and Saskatchewan, risks relating to water availability may become an even greater threat under drought and climate change conditions.



Federal Protection

The Mountain Sucker, Milk River populations, is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

Fisheries and Oceans Canada is currently consideration the listing of the Mountain Sucker, Milk River populations as Threatened under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available online at AquaticSpeciesAtRisk.ca or on the SARA Registry at 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.



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.

6 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, Milk River populations (2011)

    This small freshwater fish is limited to the Milk River basin of southern Alberta and Saskatchewan. It has a small area of occupancy and number of locations (8) that make it particularly susceptible to habitat loss and degradation from altered flow regimes and drought 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 (2017)

    His Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, pursuant to subsection 27(1) of the Species at Risk Act, makes the annexed Order Amending Schedule 1 to the Species at Risk Act.

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.

Consultation Documents