• Whitefish, Mountain

Latin name

Prosopium williamsoni

Other names

Rocky mountain whitefish, Williamson’s whitefish, grayling; French: ménomini des montagnes.


The mountain whitefish is long, slender, and almost cylindrical, though not quite the same as the round whitefish. It belongs to the species called "round whitefish". The mountain whitefish is less compressed on the sides than the lake whitefish. It is silver throughout, dark brown to olive or greenish-blue-gray on top, with scales that often have dark edges, and pelvic and pectoral fins that may have an amber tint in adults. The small mouth is slightly subterminal and the snout protrudes well beyond it. The caudal fin is forked, with 74 to 90 scales on the lateral line and 19 to 26 gill rakers.


Mountain whitefish are endemic to lakes and streams in the northwestern United States and southwestern Canada. It occurs inland in Alberta and Wyoming, overlapping the range of lake whitefish and slightly overlapping the range of round whitefish.


Typically found in rivers and fast, clear or muddy sections of large streams and lakes, mountain whitefish are usually found in stream channels in summer and in large pools in winter. They prefer temperatures of 46° to 52°F and are found in deep water in some lakes, although in northern lakes they usually stay no deeper than 30 feet.


Mountain whitefish can grow to 221⁄2 inches and 5 pounds. The world all-tackle record is held by a 51⁄2-pound fish caught in Saskatchewan in 1988. Mountain whitefish can live to be 18 years old.

Life history and Behavior

Spawning occurs from October to December in shallow, gravelly streams or sometimes in lakes with water temperatures of 42°F or lower. Parents do not guard the eggs, which incubate over the winter and hatch in the spring.

Food and feeding habits

Mountain Whitefish feed primarily on benthic organisms such as aquatic insect larvae, mollusks, fish and fish roe (including their own), as well as plankton and surface insects when larger food sources are not available.


No information

Phylum Chordata
Class Actinopterygii
Squad Salmoniformes
Family Salmonidae
Genus Prosopium
Species P. williamsoni
Conservation status No information
Habitat Pelagic
Life span, years 9
Maximum body weight, kg 2.9
Maximum length, cm 70
Sailing speed, m/s No information
Threat to people Edible
Way of eating Bentophage

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Whitefish, Mountain

Tags: Whitefish, Mountain