Photo: Naturalist Observation, c. 1912.
Species

Mountain Whitefish

Native salmonid (Prosopium williamsoni) of clear, cold rivers and lakes across western North America — from the Mackenzie River drainage in the Northwest Territories through western Canada and the northwestern U.S. A schooling bottom-feeder that holds in deep pools and swift runs alongside trout, and one of the few reliable fly targets through winter, taken by nymphing deep.

Key points

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Range: western North America — the Mackenzie, Pacific (including the Fraser and Columbia), Hudson Bay and upper Missouri drainages, through western Canada and the NW U.S. (source). Kootenay rivers include the columbia river, kootenay river, elk river, and duncan river priority waterway profiles 2026 07.
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Feeding habits: Subterminal mouth adapted for bottom feeding. Primarily consume aquatic insect larvae, such as midges, stoneflies, and small mayfly/caddis nymphs.
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Tactics: High-density nymphing near the bottom using small fly patterns (#14–18 bead-head Pheasant Tails, Hare's Ears, or brassies). Often school in deep pools, so finding one often leads to multiple catches.

Fishing by region

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Regulations, seasons, and the waters to target vary by region — in the Kootenays, see Beyond Trout in the Kootenays.

Open questions

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The exact role of mountain whitefish as competitors vs food source (juveniles) for trophy bull trout. #open

Related

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elk river — major whitefish stream.
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columbia river — major whitefish stream.
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prince nymph — effective fly pattern.

Sources

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Priority Waterway Profiles — river presence.
•
Wikipedia — Mountain whitefish — western North American range.
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