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Rainbow Trout

Rainbow Trout

Rainbow Trout (Oncorhynchus mykiss) in Idaho are actually represented by several distinct forms, most notably the native redband trout subspecies (Oncorhynchus mykiss gairdneri) found in the Columbia River drainage.

Redbands are distinguished from regular rainbow trout by their larger, more rounded spots and parr marks that remain into adulthood.

Idaho steelhead are also rainbow trout genetically - seafaring forms of redband trout that migrate over 700 miles from the ocean to spawn.

Scientific Name: Oncorhynchus mykiss

Also known as redband trout subspecies (Oncorhynchus mykiss gairdneri)

Physical Characteristics:
  • Redbands are distinguished from regular rainbow trout by their larger, more rounded spots and parr marks that remain into adulthood.
  • Adults typically ranging 12-20 inches and 1-4 pounds in streams, though lake-dwelling fish can grow larger.

What to know

Habitat Distribution

  • In Idaho, rainbow trout inhabit cold freshwater streams, rivers, lakes, and reservoirs where average temperatures stay below 65 degrees year-round, preferring well-oxygenated water from high-gradient mountain streams.

Key Locations

  • Key waters include the South Fork Snake River, Henry's Fork, North Fork Coeur d'Alene River, Boise River, and numerous alpine lakes.
  • Silver Creek requires technical presentations with long leaders and small flies due to selective trout.

Rainbow Trout FAQ

Answers from onWater's species guide.

What are the best lures and bait for Rainbow Trout in Idaho?

Kastmaster spoons (1/8-1/4 oz), Roostertail spinners (1/16-1/8 oz), Mepps Aglia spinners (sizes 1-2), and various trolling spoons like Needlefish and Dick Nites for lake fishing.

What flies work for Rainbow Trout in Idaho?

Essential fly patterns include Woolly Buggers (olive, brown, black) for streamers, Blue-Winged Olive soft-hackles (sizes 14-18) for baetis hatches, Griffith's Gnats (sizes 16-20) for midge clusters, Prince Nymphs (sizes 8-12) as stonefly imitations, and San Juan Worms for high water conditions.

When is the best time to fish for Rainbow Trout in Idaho?

Best fishing times for rainbow trout in Idaho are spring (March-June) when post-spawn fish are actively feeding to replenish nutrients, summer (June-August) during peak hatch activity, and fall (September-October) when cooler temperatures increase activity.

How do you catch Rainbow Trout in Idaho?

Spring fishing calls for nymphs and streamers fished deep, while summer offers excellent dry fly opportunities during major hatches like salmon flies, green drakes, and PMDs. High water periods after runoff can be productive with darker flies fished against banks.

What do Rainbow Trout eat?

Rainbow trout are opportunistic feeders with a diverse diet including aquatic insects (mayflies, caddisflies, stoneflies), terrestrial insects like grasshoppers and ants, crustaceans, small fish, fish e.g.gs, plankton, snails, and leeches.

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