Here are Colorado's major summer hatches in basic chronological order as they appear in the summer along with some fly choices and fishing tips. Don’t forget many of these hatches overlap and trout may feed on several different hatches in the same day.
The first major hatch of the summer and at two to three inches in length, Salomflies are also the biggest insect we’ll see all year and the hatch begins before the official start of summer, sometime in late May or early June. Primarily found on the upper Colorado around Pumphouse, smaller numbers of these big stoneflies are also present in the Eagle and Roaring Fork Rivers. Try a # 2-6 brown or black Pat’s Rubberleg, Yuk Bug or Bitch Creek for the salmonfly nymph and a Rogue River Stone, Orange Stimulator or Orange Noble Chernobyl for the adult. While trout will hammer nymph patterns for weeks before the actual hatch, the adults are only around for a few days and your timing must be superb to experience good dry fly fishing.
Green Drakes are Colorado’s largest mayfly species. These #10-12 olive mayflies are found in the largest numbers on the Roaring Fork River but also hatch on the Eagle and Gore Creek. Their emergence varies from mid-June to early July depending on stream flows and water temperature. The Zug Bug, Mercer’s Poxyback Drake, and Olive Guide’s Choice are all good nymph patterns while the Green Drake Parawulff, Lawson’s Cripple Drake and House and Lot Variant are great dry flies.
The summer hatch of caddis usually begins right after runoff begins to recede in mid to late June on the Eagle and Roaring Fork Rivers. These tan caddis run #12-16 and hatch for several weeks with trout feeding heavily on the surface. Soft Hackle Pheasant Tails, Guide’s Choice Hare’s Ear and Barr’s Graphic Caddis will work dead drifted or on the swing while a Tan Stimulator, Tan Elk Hair Caddis and Tan Foam Caddis will all work on the surface.
PMDs or Pale Morning Dun mayflies hatch beginning in early July on the Colorado, Eagle and Roaring Fork and trout seem to prefer them as a late morning change of pace from caddis. Colorado’s PMD are a pinkish orange color and average #16-18. Good nymph patterns include a brown Micromayfly, Trina’s Bubbleback PMD, and Quasimodo Pheasant Tail. For risers try a Pink Foam Parachute, Melon Quill or PMD Parawulff.
Golden Stoneflies are the Salmonfly’s slightly smaller (#4-10), less popular but more numerous and more important cousin. They hatch on all area rivers from early July through the end of summer. The adults emerge mostly at night but nymph patterns can be effective anytime while a big Golden Stonefly dry fished in the early morning or when hoppers are around can bring explosive strikes. For nymphs it’s hard to beat a Tan Pat’s Rubberleg, Twenty Incher or VVA Rubberleg Hare’s Ear. Dries that work well are a Tan Chubby Chernobyl, Yellow PMX, or a Peacock Stimualtor.
Yellow Sallies are another stonefly but at #14-18, much smaller in size. These bright yellow insects start hatching in early July often alongside caddis and PMDs on the Eagle and Roaring Fork. They’re slow and trout like them. Look for patterns that feature a red, pink or orange butt for added attraction and realism. Mercer’s Microstone, Kyle’s BH Yellow Sally, are good nymphs while a Yellow Foam Stone or Yellow Elk Hair Caddis will fool surface feeders.
Usually, by mid-July in Colorado a variety of terrestrial insects such as ants, beetles and grasshoppers are on the menu. They’re a valuable food source on any piece of moving water from mid-summer through early fall but the trout on the Colorado River seem especially inclined to pound hoppers fished tight to grassy banks. Terrestrials, while they can be fished drowned and under the surface are really most effective as dry flies. Here’s some favorite patterns: Gould Half-Downs, Royal and Yellow PMX, Chubby Chernobyl, Noble Chernorbyl, and the Fat Albert.
Red Quill mayflies are often seen hovering in packs of adults over the water. As their name implies they are a rusty red color in size #12-16. Most common on the Colorado but also important on the Eagle and Fork, they begin hatching in August. For nymphs, a simple Pheasant Tail or Red Copper John is a good imitation while a Royal Wulff with a trailing Rusty Spinner are top dry fly choices.
Another mayfly, the Trico, or "the white-winged curse", is a diminutive #20-24 olive and black mayfly with bright, whitish wings. They hatch in late summer around mid-August on all of Central Colorado’s major trout fisheries. Trico Spinners, small Royal Wulffs and Renegades are especially important to trout sipping on the surface in slow water on the Colorado. Drowned trico imitations, Barr’s Trico Emerger and black midge emergers work well in faster water on stream like the Eagle or Roaring Fork.
When the small Blue-winged Olive mayflies begin hatching with the arrival of cooler nights in late August or early September, it’s a sure sign that summer is coming to an end. The same bug that hatches in the spring, this late summer/early-fall version tends to run a little smaller at #20-22. They can be found on any trout stream but hatch in the largest numbers on the Colorado River. Barr’s BWO Emerger, Sparkle RS-2 and the WD-50 are ideal nymph patterns while the Adams Parawulff, Foam BWO Parachute and the good old Parachute Adams are go-to dry flies.
With some basic knowledge of these ten summertime hatches, anglers in Colorado can expect to have good fly fishing no matter when they hit the river during summer. For more information on the best fly patterns, when to fish Colorado or to book a guided fly fishing trip, check in with the Vail Valley Anglers fly shop in Edwards, Colorado or check us out online.
Brody Henderson, Guide and Content
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