Can you keep a trout, arctic char, grayling and mountain whitefish in Colorado?

No minimum size statewide. Brook trout 8 inches or shorter may be kept in addition to this limit, up to 10 more per day — a rule meant to thin out overpopulated brook trout in small streams. Applies at Clear Creek at the stretch this site tracks (Golden/canyon area) — the flies-and-lures-only, catch-and-release special rule only covers a short alpine headwater stretch near Loveland Pass, well upstream.

CPW source page

One of Colorado's best-known Gold Medal trout stretches. 16-inch minimum and a 2-fish bag replace the statewide 4-fish, no-minimum default, and only artificial flies and lures may be used.

CPW source page

2-fish bag replaces the statewide 4-fish default along essentially the entire Eagle River, from above Minturn down to where it meets the Colorado River at Dotsero. No minimum size or gear restriction is stated for this stretch, unlike the flies-and-lures-only South Platte and Clear Creek special waters.

CPW source page

What we left out on purpose

• Walleye/saugeye/sauger and white bass/striped bass/wiper both carry a higher combined limit (10 and 20 respectively) specifically on the Arkansas River and the South Fork Republican River. Neither water is covered by this site, so the higher regional numbers are not modelled — the statewide figures apply everywhere this site actually reports on.
• Clear Creek carries a flies-and-lures-only, catch-and-release special regulation from its headwaters near Loveland Pass downstream to Duck Lake — a short alpine stretch far above Golden, where this site's Clear Creek report is anchored. The statewide trout rule is used here because the site's location sits well below that special-regulation stretch.
• This silo covers finfish only. Colorado's crayfish and bullfrog rules (both unlimited statewide) are not modelled, consistent with every other state in this silo.
• Aquatic tiger salamander larvae (a legal live-bait/food species in Colorado under 5 inches, gilled) is not a finfish and is not modelled here.
• Colorado's countless named Gold Medal and special-regulation stretches beyond the four waters this site actually reports on (Deckers, Dream Stream, Eagle River, Clear Creek) are not modelled — the same restraint applied to Louisiana's and Mississippi's dozens of named-water exceptions.