Rainbow Trout
Oncorhynchus mykiss · Salmonidae
Also known as: Steelhead (anadromous form), Redband trout
A hard-fighting, acrobatic salmonid and the world's most widely stocked trout.
- Typical size
- 0.3–2 kg (1–4 lb)
- Max size
- Lake-run fish and steelhead exceed 9 kg (20 lb).
- Water
- Freshwater
- Best season
- Spring and fall; cool water through summer at altitude.
Identification
Silvery body with a broad pink-to-red lateral band and heavy black spotting over the back, sides, and tail.
Habitat & Range
Cold, clean rivers and lakes; the sea-run steelhead form migrates to the ocean and returns to spawn.
Native to the Pacific drainages of North America and eastern Asia; introduced on every continent except Antarctica.
Diet & Feeding
Aquatic and terrestrial insects, crustaceans, fish eggs, and small baitfish.
Spawning & Reproduction
Spring spawner (unlike the fall-spawning brown). Females cut redds in clean gravel riffles.
Spawning windowSource-verified
- Run begins
- Feb 15
- Peak
- Apr 10
- Ends
- May 31
- Redd temperature
- 42–44°F
Spring spawner, February to May, with redd construction from about 42-44F - the mirror image of brown and brook trout, which spawn in autumn on falling temperature. In Colorado the timing is often academic: whirling disease eliminated many wild rainbow populations from the mid-1990s, so a large share of the state's rainbows are stocked fish that never reproduce successfully. CPW has run a long recovery programme breeding disease-resistant strains, collecting over 500,000 eggs since 2014 to stock into whirling-disease-positive rivers.
Timing is modelled for a mid-latitude reference population — fish the thermometer, not the calendar. Based on 2 cited sources.
Spawning timing by location
Spawning tracks water temperature, so the calendar shifts with latitude and elevation. These break rainbow trout timing down by state and water body.
- When Do Rainbow Trout Spawn in Colorado?
Colorado rainbow trout spawn in spring, February to May, at 42–44°F. The complication: whirling disease eliminated most wild rainbow reproduction in the 1990s, so many of the state's rainbows never spawn successfully at all.
How to Catch
Match the hatch on rivers; on stocked lakes, suspend bait off the bottom. Expect spectacular jumps once hooked.
Best techniques
- Fly fishing
- Float/bobber fishing
- Spinning
- Drift fishing
Lures & baits
- Nymphs & dry flies
- Prepared bait & salmon eggs
- Spinners & spoons
- Worms
Best season: Spring and fall; cool water through summer at altitude.