Prosopium williamsoni
Mountain Whitefish
NS
G5
Collection Details
Specimens
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Records
Taxonomic Hierarchy
Actinopterygii (Ray-finned Fishes)
Salmoniformes
Salmonidae (Trouts and Salmons)
Prosopium
Prosopium williamsoni (Mountain Whitefish)
Description
This species account was compiled from
FishBase (Froese, R. and D. Pauly. Editors. 2025. FishBase. World Wide Web electronic publication. www.fishbase.org, version 04/2025.)
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Characters
Body shape: fusiform / normal. Body slender, elongate, nearly cylindrical in cross section but variable, more compressed laterally than round whitefish. Head short; eye moderate, its diameter less than snout length; snout more or less pointed, compressed laterally, pinched, rounded in lateral view, a single flap of skin present between nostrils. Mouth small, ventral in position, overhung by snout; maxillaries extending posteriorly almost to anterior margin of eye in adults. Teeth small, restricted to a small patch on tongue and on gill rakers in adults, although small teeth may be present on the premaxillaries in young, but absent from jaws, vomer, palatines and pre maxillae in adults. Overall coloration silvery, but light or dark brown or olive on back, becoming silvery in sides and white below. Scales, specially on back, may have pigmented borders. dorsal fin often dusky, pelvic and pectoral fins in adults with amber tint. Striking features: none.
Distribution
North America: Mackenzie River drainage in Northwest Territory, Canada south through western Canada and northwestern USA in the Pacific, Hudson Bay and upper Missouri River basins to Truckee River drainage in Nevada and Sevier River drainage in Utah, USA.
Habitat Associations
Freshwater. benthopelagic. depth range 5-20 m. Found in: streams, lakes.
Biology
Occurs in lakes and fast, clear or silty streams. Feeds mainly on benthic organisms such as aquatic insect larvae, mollusks, fishes, and fish eggs (including their own) but may feed on plankton and surface insects when the need arises (Ref. 1998).
Max length: 70.0 cm TL; common length: 23.4 cm TL; max weight: 2920 g; max age: 17 years.
Reproductive mode: dioecism; fertilization: external; nonguarders (open water/substratum egg scatterers); parental care: none.
IUCN Red List Status: Least Concern (LC), assessed 2016-07-27. Resilience: Low (tmax=14).
Commercial or Environmental Importance
Fisheries: minor commercial; gamefish.
References
Scott, W.B. and E.J. Crossman (1973) Freshwater fishes of Canada. Bull. Fish. Res. Board Can. 184: xi+1-966.
Page, L.M. and B.M. Burr (1991) A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.
Balon, E.K. (1975) Reproductive guilds of fishes: a proposal and definition. J. Fish. Res. Board Can. 32(6):821-864.
Thompson, G.E. and R.W. Davies (1976) Observations on the age, growth, reproduction, and feeding of mountain whitefish (Prosopium williamsoni) in the Sheep River, Alberta. Trans. Am. Fish. Soc. 2:208-219.
IGFA (2001) Database of IGFA angling records until 2001. IGFA, Fort Lauderdale, USA.
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