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Colorado River Hatches

Hatches and Seasons
You can fish the Colorado 365 days a year if you know where and in what seasons to find the river's most important hatches.

Caddis hatch all summer long on the Colorado, starting with a major Brachycentrus hatch in early spring before runoff. This may be the most dependable hatch on the river, and the dry-fly event of the year if conditions are right. The hatch starts in late April downstream of Glenwood Springs and moves upstream as water temperatures become more favorable, erupting on the Upper Colorado in early May and in Middle Park sometime after Mother's Day.

If you find the caddis before the mud comes, you'll see blanket hatches so thick you'll lose your fly in the blizzard. If this happens, try flies that are different from the rest. A #16 Renegade fished dry or on the swing is deadly in these situations.

Several species of caddis combine to provide steady late-afternoon hatches through early summer, and they gradually taper down (both in size and quantity) through the summer until they disappear in late September. Stimulators, Elk-hair Caddis, and King River Caddis (#14-#18) are among those that take fish. October Caddis can be a factor late in the year in Middle Park. Again, Stimulators (#10-#12) are a good choice.

The salmonfly hatch on the Colorado River is rarely seen. Your best chance to see trout chowing on big salmonflies (Pteronarcys) is in Middle Park during the last week of May or first week of June. There are also earlier, localized salmonfly populations downstream in the Pumphouse/Radium area, and below Glenwood Springs. Wherever there is rocky, well-oxygenated water, there are salmonflies.

If you witness the hatch, or better yet, the egg-laying flights of the adult insects, you'll not soon forget the experience. The nymphs migrate to the shallows prior to emergence, and crawl out of the water onto nearby rocks and vegetation where they split their nymphal shucks and emerge as winged adults. These airborne Godzillas of the insect world are like newborn robins, and every one of them flies like they left the nest a few days too early. Their first attempts at flight are often cut short by an awkward emergency water landing. They rarely survive on the water long, because the trout know they are a great meal. Big #6-#8 dry stonefly patterns like the Rogue Stone, Stimulator, Turks Tarantula, or Chernobyl Ant catch trout all summer. The same patterns in smaller sizes (#6-#10) are also effective imitations for Golden Stoneflies, which are most commonly seen early mornings in July, or on overcast afternoons below Glenwood Springs.

Stonefly nymphs are productive all year round, and the local opinion is that you don't need anything particularly realistic. Halfbacks, Prince Nymphs, and 20-inchers in sizes #6-#10 are Colorado River favorites.

Yellow Sallys (#14) catch smaller fish (12 to 15 inches) below Glenwood Springs, but the big fish rarely hunt them. In Middle Park, the hatch is more pronounced, and a Yellow Sally pattern can be an effective searching pattern. Look for these bugs around July 4 in Middle Park, and up to two weeks earlier in the lower river.

The Red Quill is an important hatch in Middle Park and the Upper Colorado between the Pumphouse Recreation Area and State Bridge. The bugs start hatching as soon as the river begins to rise with melting snow in May, and continue through June. When the hatch is on, the trout can become downright foolish, taking almost any #14-#16 mayfly imitation. Duns hatch in the afternoon, and the spinners mate over the riffles in the last hour of the day. Caddis usually hatch during this same time period, and it's not unusual to fish dry flies from noon until dark during this part of the year. Don't try to be home for dinner; you'll miss the day's best fishing.

The first and last mayflies of the year are Blue-winged Olives (Baetis and Pseudocleon). They are the least sensitive to sediment, and can be found hatching on all sections of the river in April and May, and again in the fall in September and October. Because these flies are so small (#16-#20), you should look for areas where the insects collect. Try backwaters, foamy back eddies, and in the flat water below riffles. Trout won't chase the flies, but they will station themselves in places where they can eat their fill with little effort. While spring and fall are the most common hatch periods, you can see Olives any day of the year. A cloudy afternoon in June or an August rain shower can bring on surprising hatches.

Midges hatch on the Colorado year-round, but are most important in March and April, and again in October and November. The heaviest hatches are in Middle Park just downstream of the confluence of the Williams Fork, and in the lower river, below Glenwood Springs. Between November and March, the lower river is at its clearest, and warmer water temperatures keep the fish feeding through the winter.

Midge pupa imitations like the Miracle Nymph, Brassie, and RS-2 are favored patterns, but almost anything #18 or smaller will catch fish. When trout sip midge pupae near the surface, coat your leader with floatant to within about 12 inches of your fly. When fish are taking midges, they are more likely to take a small fly just under the surface than a dry fly.

You can find PMDs on the Colorado in July. Look for them to appear on the lower river around July 4 and in Middle Park around mid-month. They last two weeks or more. On the lower river, all the mayflies are Texas-size, and guides tie their bugs correspondingly large. In Middle Park, the PMDs are a standard #14-#16; near Glenwood Springs, #12-#14 is not too large. Pink-bodied parachute or Sparkle Dun variations are most effective.

The best Trico fishing on the Colorado is in Middle Park, particularly in the western half of the valley near Elktrout Lodge. There are three relatively unknown sections of public BLM land in this area, all of them bordered by private property. Visit the BLM office in Kremmling for a map and directions to this water.

The Trico spinner fall usually happens when the air temperature is about 70 degrees F., so you'll need to fish early in the morning during the hot days of late summer, and later in the morning as fall approaches. Duns hatch in the late evening and early morning, before the spinner fall. A #20 Parachute Adams can catch fish when the duns are hatching; any #20 fly with a dark body and white spent wings works during the spinner fall.

Rocky runs and riffles of the lower and upper Colorado have good populations of Green Drakes. The hatch starts about June 1 below Glenwood Springs, and as late as the middle of July near the mouth of Gore Canyon. The first few weeks of opportunity are usually lost to high muddy water, but as the water comes down, a #12-#14 Quigley Cripple or Green Drake Hair-wing Dun can bring fish to the surface.

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