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© 2026 Barbless.co. Flow and gauge data from USGS; weather from Open-Meteo. · v2026.10.18.2

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  4. Westslope Cutthroat Trout

Updated June 25, 2026

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Westslope Cutthroat Trout: fish species profile

Fish › Trout

TroutSalmonidaeG4 (Apparently Secure) · ESA: Not listed · Idaho: S4

Westslope Cutthroat Trout

Oncorhynchus clarkii lewisi

Idaho’s native westslope cutthroat thrives in cold, clear mountain rivers and eager dry-fly water.

Overview

Size range

10–39 in

Size range

10–39 in

Size range

Typical adult length in the waters we cover.

Water temperature

Coldwater

Water temperature

Coldwater

Water temperature

Preferred thermal regime for this species.

Active season

Spring through fall

Active season

Spring through fall

Active season

When anglers most often encounter this species.

Origin

Native

Origin

Native

Origin

Stocking and native history where this species is found.

Habitat

Headwater Streams, Rivers & Large Rivers, Lakes & Reservoirs

Habitat

Headwater Streams, Rivers & Large Rivers, Lakes & Reservoirs

Habitat

Primary water types where this species is found.

About Westslope Cutthroat Trout

Westslope cutthroat trout are native to northern and central Idaho and remain a hallmark fish of clear, connected mountain rivers like the St. Joe, Lochsa, Selway, Kelly Creek, and Coeur d’Alene drainages. This coldwater trout belongs to the salmon family and is especially at home in smaller streams and river sections with clean gravel and gentle gradients.

Westslope Cutthroat Trout Silhouette

Westslope Cutthroat Trout species silhouette
Primary

Behavior

spawning
Spawns in freshwater over gravel, with fish moving into suitable tributary or stream habitats in spring to early summer depending on runoff and elevation.
feeding style
An opportunistic coldwater feeder that takes insects, crustaceans, small fish, and surface food when conditions line up.
seasonal notes
Best activity often tracks cool water and insect hatches, with fish using pocket water, seams, and softer current near cover in clear mountain streams and rivers.

Habitat

water types
small streams, mountain rivers, tributaries, coldwater rivers
preferred holds
Look for them in clear, cold runs and riffles with gravel bottoms, gentle-to-moderate gradients, undercut banks, wood, boulders, and current seams near tributary influence.

Where Found

Blue Ribbon waters

  • Westslope cutthroat trout

    Kelly Creek

  • Westslope cutthroat trout

    Lochsa River

  • Westslope cutthroat trout

    Middle Fork Salmon River

  • Westslope cutthroat trout

    North Fork Coeur d'Alene River

  • Westslope cutthroat trout

    Saint Joe River

  • Westslope cutthroat trout

    Selway River

Recommended waters

  • Westslope cutthroat trout

    Cayuse Creek

  • Westslope cutthroat trout

    Coeur d'Alene River

Diet

They feed mostly on insects, but also take crustaceans and small fish when the opportunity is there.

  • AntInferred
  • BeetleInferred
  • Blue-winged OliveInferred
  • CaddisInferred
  • Golden StoneflyInferred
  • GrasshopperInferred
  • Green DrakeInferred
  • Mahogany DunInferred
  • March BrownInferred
  • MidgeInferred
  • October CaddisInferred
  • Pale Morning DunInferred
  • SalmonflyInferred
  • SculpinInferred
  • SkwalaInferred
  • Yellow SallyInferred

Angler Tactics

tactics
Keep presentations light and natural in clear water. Cover pocket water, seams, and shaded banks, and match hatches or switch to terrestrials when fish are looking up.
effective methods
dry flies, nymphs, small streamers, terrestrials

Regulations

Rules can vary widely by river, drainage, season, and whether fish must be released, so always check the current Idaho Fish and Game seasons and rules for the specific water before fishing.

Regulations vary by water. Check current Idaho Fish and Game rules before fishing.

Conservation

Status: Native to Idaho (S4)

G4 (Apparently Secure) · ESA: Not listed · Idaho: S4

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OverviewSilhouetteBehaviorHabitatWhere FoundDietAngler TacticsRegulationsConservation

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On this profile

  • 9 waters
  • 16 food sources
  • 1 photo

Westslope cutthroat trout

South Fork Coeur d'Alene River