Trout Species of Colorado

Rainbows are the fish most Colorado anglers picture, and the South Platte tailwaters — Cheesman Canyon, the Dream Stream, Deckers — grow famously selective, well-fed fish in cold, regulated flows below the dams. The Blue River below Dillon is another classic, where mysis shrimp pushed through the dam produce heavy, silver rainbows. Identify them by the pink lateral stripe, profuse black spotting over the whole body, and the squared tail. Whirling disease gutted Colorado's wild rainbow reproduction in the 1990s, so many populations are stocked or built on disease-resistant strains — but the tailwater fish hold and grow like wild trout.

Brown trout are the backbone of Colorado's rivers — they hold in nearly every major drainage, from the Colorado and Roaring Fork to the Arkansas, Taylor, and Gunnison. Introduced from Europe, they out-survived the whirling disease that hit rainbows and now sustain themselves wild across most of the state. Look for buttery gold flanks, black and red spots, and red-orange spots ringed in pale halos. They're the wariest fish in the river and grow the largest; in fall they turn aggressive and territorial as they move to spawn, which is when the biggest browns of the year come to a streamer.

The Rio Grande cutthroat is Colorado's state fish, endemic to the southern Rocky Mountains and native to the high tributaries of the Rio Grande in the San Juans and Sangre de Cristos. It's the southernmost cutthroat on Earth, now restricted to a fraction of its historic range and managed catch-and-release in its native streams. Identify it by the orange-red throat slash, fine spots concentrated toward the tail, and rich golden-bronze sides.

On the west slope, the Colorado River cutthroat is the native trout of the upper Colorado, Yampa, and White drainages. It's often the most vividly colored of the three — deep crimson and brassy flanks on spawning fish — with the classic throat slash and tail-weighted spotting. Genetically pure populations survive mostly in isolated headwater streams above barriers that keep introduced rainbows out, and they're managed to prevent hybridization.

The greenback cutthroat is the native trout of the South Platte and Arkansas drainages on the Front Range, and one of the great conservation stories in American fishing — once thought extinct, then rediscovered in a single tiny population in Bear Creek near Colorado Springs. It's federally threatened, the subject of an intensive reintroduction effort, and any greenback you encounter is catch-and-release, often in closed or specially regulated water. Look for the largest, roundest spots of any Colorado cutthroat, crowded toward the tail, over deep green-and-rose flanks.

Brook trout — actually char, not trout — were introduced from the East and have naturalized across Colorado's cold high-mountain streams, beaver ponds, and alpine lakes, often where nothing else survives the winter. They're gorgeous: dark green vermiculated backs, red spots in blue halos, and white-edged orange fins. But in small headwaters they out-compete native cutthroat and frequently stunt, so many high-country drainages carry liberal or unlimited bag limits — keeping a few brookies for the pan is often encouraged. Check the local rule.

Lake trout — another char, also called mackinaw — live in Colorado's big, deep, cold reservoirs. Blue Mesa Reservoir on the Gunnison produces some of the largest lakers in the lower 48, and Eleven Mile Reservoir on the South Platte holds them too. They're a deep-water fish most of the year — light spots on a dark gray-green body and a deeply forked tail set them apart — and more a lake-fishing or ice-fishing target than a river quarry, though they pull hard when you find them shallow in spring and fall.