The following fly hatch chart covers the major hatches that occur throughout Colorado’s main river systems. Hatch species—as well as beginning and ending dates—may vary from river to river.

Colorado hatches go through three basic stages: Nymph (Larvae), Pupae/Emergence, and Adult. The nymph stage typically comes right before the actual hatch and offers a great opportunity for anglers to target trout using subsurface nymph patterns and wet flies.

Largest Colorado Hatches and Recommended Fly Patterns

Fly hatches provide the majority of food for Colorado’s river dwelling trout populations. Anglers will experience the highest catch rates when using fly patterns that match the hatch for the date and location of the river they’re fishing. The following are recommended fly patterns for Colorado’s major hatches.

Salmonfly

The salmonfly hatch is one of the first major hatches to occur in Colorado. Measuring 3-5 inches, salmonflies are one of the largest insects to hit the water. They’re mouthful for a hungry trout and provide for some of the most exiting fly action on the river all season long. It’s the only time of year anglers get to cast a giant size fly on stout tippet to hordes of aggressively feeding trout.

The largest salmonfly hatches occur in the upper Colorado river. Smaller hatches occur in several of the trout fisheries in west central Colorado including Roaring Fork and Eagles Rivers, as well as several tributaries of the Colorado River.

While salmonfly adults are only available as a food source for the short window during hatches, salmonfly nymphs are available year round.

Salmonfly hatches only last for a short time and peak hatch only lasts for a few days. Most salmonfly fishing is with nymph patterns pre-emergence. To dry fly fish with salmonflies, you have to hit the hatch just right.

Blue Winged Olive (BWO)

BWO hatches occur twice each year—once in the spring and again in the fall. Early hatches begin in late March and extend through April. Fall hatches run from early September through October. Spring BWO are a little larger than fall hatches which run #20-22. BWO hatches are found through Colorado’s river, but are most abundant on the Colorado River.

Green Drake

Green Drakes hatches are found primarily in three rivers, the Eagle River, Gore Creek, Piney River, and in largest numbers along the Roaring Fork River. Hatches typically begin in early July and run through August.

Caddis

Caddis hatches kick into full gear in mid to late June just after spring runoff and river flows begin to subside. Caddis hatches are most abundant on the Eagle and Roaring Forks Rivers. This hatch runs for several weeks on the surface offering excellent opportunities for dry and wet fly anglers.

Pale Morning Dun (PMD)

PMD hatches enter the scene mid June early July on the Colorado River, its tributaries, and Eagle and Roaring Fork Rivers. PMD hatches overlap with caddis hatches and trout are equally eager to take either fly. Colorado Pale Morning Dun mayflies are a pinkish orange in color from size 16-18 in the spring, and slighly smaller (#20) in the later summer. PMD hatches offer excellent nymph and dry fly fishing opportunities.

Golden Stonefly

The best way to think of a Golden Stonefly is a Salmonfly but smaller. Golden Stonefly hatches don’t garner the same attention from anglers as Salmonfly hatches but theiy’re more abundant, and often more productive for fly fishing. Golden Stoneflies hatch from June through mid August on most Colorado rivers.

Yellow Sally

Yellow Sally is one of the smallest of the stonefly species. Hatches start in late June early July and overlap with PMD and caddis hatches. Yellow Sally hatches are most abundant on the Eagle, Colorado and Roaring Fork rivers. They are also prevalent on the South Platte, Gunnison, and Arkansas rivers. Sally hatches provide some of the most reliable fly fishing of the year.

The most effective fly patterns incorporate a orange, pink or red butt.

Red Quill

Red Quill is a small mayfly (#12-16) that is redish in color. Clouds of Red Quill are often observed hovering just above the surface of the water. Red Quill hatches are most prevalent on the Colorado, Eagle and Roaring Fork rivers.

Trico

Trico is one of the smallest mayflies in North America. They have bright white wings that contrast against their darker olive and black bodies. Anglers sometimes refer to Tricos as the “white-winged curse” because they’re a difficult fly to imitate. They hatch late June to mid-August in Central Colorado’s trout rivers. Trico hatches are most prolific on Elevenmile, Deckers, Cheesman Canyon, Arkansas, Yampa, Gunnsion, Williams Fork and Colorado Rivers.

Terrestrials

Terrestrial insects including ants, beetles and grasshoppers hit the menu in July. From mid-summer through early fall terrestrials become a valuable food source for foraging trout. Fishing terrestrial dry fly patterns tight against grass laden banks is an effective method for getting bites. While terrestrials can be fished subsurface they’re more effective as dry flies.

Recommended fly patterns:

• Gould Half-Downs
• Royal PMX
• Yellow PMX
• Chubby Chernobyl
• Noble Chernobyl
• Chernobyl Ant
• Fat Albert
• Flying Black Ant
• Madam X