Mountain whitefish

The mountain whitefish (Prosopium williamsoni) is one of the most widely distributed salmonid fish of western North America. It is found from the Mackenzie River drainage in Northwest Territories, Canada through western Canada and the northwestern USA in the Pacific, Hudson Bay and upper Missouri River basins to the Truckee River drainage in Nevada and Sevier River drainage in Utah.

Habitat

The mountain whitefish are commonly found in mountain streams and lakes, favoring clear cold water and large deep pools of at least a meter's depth; the Lake Tahoe population lives just above the bottom in deeper water.

Distribution

This species occurs throughout the western half of North America, as far north as the Mackenzie River (Canada) and the drainages of the Hudson Bay, in the Columbia River, upper Missouri River, upper Colorado River, Adirondack Lakes of New York, and Lake Champlain.

Behaviour

Mountain whitefish are demersal feeders, stirring up the substrate with pectoral and tail fins to expose insect larvae and other invertebrates, including snails, crayfish, and amphipods. Their main feeding time is in the evening, but they will also take drifting prey during the day. The mountain whitefish frequently feeds in the lower strata of streams, but populations may rise to the surface to prey on hatching insects, including mayflies. Mountain whitefish fry are a common food source for other trout species.