The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Prosopium williamsoni
Prosopium williamsoni
(Mountain Whitefish)
Native Transplant

Copyright Info
Prosopium williamsoni (Girard, 1856)

Common name: Mountain Whitefish

Taxonomy: available through www.itis.govITIS logo

Identification: Scott and Crossman (1973); Wydoski and Whitney (1979); Sigler and Sigler (1987); Page and Burr (1991).

Size: 57 cm.

Native Range: Mackenzie River drainage (Arctic basin), Northern Territories, south through western Canada and northwestern United States in Pacific, Hudson Bay, and upper Missouri River basins, to Truckee River drainage, Nevada, and Sevier River drainage, Utah (Page and Burr 1991).

Native range data for this species provided in part by NatureServe NS logo
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Prosopium williamsoni are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CO195520094Cache La Poudre; Colorado Headwaters; Colorado Headwaters-Plateau; Roaring Fork

Table last updated 7/23/2024

† Populations may not be currently present.

Ecology: As with many western North American salmonids, Mountain Whitefish generally inhabit clear, cool waters (< 20° C) of high elevation streams, rivers, and lakes (Moyle 2002). Spawning occurs during late fall to early winter (October - December) in shallow areas of small tributaries or shoreline areas of lakes, primarily over gravel, rubble, or cobble bottoms (McAffee 1966; Moyle 2002). Mountain Whitefish are demersal feeders, consuming a range of benthic invertebrates, including insect larva, gastropods, and small crustaceans(McAffee; Ellison 1980; Moyle 2002).

Means of Introduction: Stocked for sportfishing in Colorado and as a game and food fish in Michigan.

Status: Established in Colorado. Extirpated in Michigan.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: Mountain Whitefish were thought to compete with juvenile and adult trout (McAffee 1966), but the diets of the two species are significant different and brook trout consume whitefish fry (Ellison 1980).

References: (click for full references)

Ellison, J.P. 1980. Diets of mountain whitefish, Prosopium williamsoni (Girard), and brook trout, Salvelins fontinalis (Mitchell), in the Little Walker River, Mono County, California. California Fish and Game 66(2):96-104.

Emery, L. 1985. Review of fish introduced into the Great Lakes, 1819-1974. Great Lakes Fishery Commission Technical Report, volume 45.

McAffee, W. R. 1966. Mountain whitefish. 299-303 in A. Calhoun, ed. Inland Fisheries Management. California Department of Fish and Game.

Moyle, P.B. 2002. Inland fishes of California. 2nd edition. University of California Press, Berkeley, CA.

Page, L.M. and B.M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Guide Series, vol. 42. Houghton Mifflin Company, Boston, MA.

Sigler, W.F., and J.W. Sigler. 1987. Fishes of the Great Basin: a natural history. University of Nevada Press, Reno, NV.

Scott, W.B., and E.J. Crossman. 1973. Freshwater fishes of Canada. Fisheries Research Board of Canada, Bulletin 184. Ottawa.

Wiltzius, W.J. 1985. Fish culture and stocking in Colorado, 1872-1978. Division Report 12. Colorado Division of Wildlife.

Wydoski, R.S., and R.R. Whitney. 1979. Inland fishes of Washington. University of Washington Press, Seattle, WA.

Other Resources:
FishBase Summary

Author: Pam Fuller, and Matt Neilson

Revision Date: 6/29/2023

Peer Review Date: 4/10/2012

Citation Information:
Pam Fuller, and Matt Neilson, 2024, Prosopium williamsoni (Girard, 1856): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=924, Revision Date: 6/29/2023, Peer Review Date: 4/10/2012, Access Date: 7/24/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/24/2024].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.