Western lakes and reservoirs offer many productive summer hatches, but only the Callibaetis hatch can be described by the method in which trout detonate on these insects--by "gulping" them.

To the best of my knowledge, the term rose from southwest Montana's Hebgen Lake and refers to the sound Hebgen's fat rainbow and brown trout make when they feast on Callibaetis. On a calm morning during the peak of a Callibaetis hatch, Hebgen's surface may be littered with dimples from feeding fish and the combined gulping sound made by these rising trout can give anglers the shakes.

Callibaetis hatch spring through fall on stillwaters throughout the West. Duns (below) have two tails, a cream underbody, and a brown or olive back. Spinners (above) are light gray with black speckled wings.

Despite its popularity among fly fishers in the West Yellowstone region, the Callibaetis hatch is mostly an afterthought to the typical angler. That's because we rarely encounter Callibaetis on rivers and creeks where most of us spend our time. Where they do hatch in decent numbers on moving water, they are often overshadowed by the excitement of the big-game bugs, such as hallowed giant stoneflies, Pale Morning Duns, caddis, and Green Drakes. Even on stillwaters, anglers are more likely to fish during a fleeting damselfly emergence than during a predictable Callibaetis hatch.

Callibaetis can be the most dominant summer insect on Western stillwaters and depending on the season, they offer a predictable chance to catch large trout on dry flies when rivers and streams are unfishable due to high, muddy water, or low, hot water. The Callibaetis hatch comes off like clockwork over a three- or four-month span on waters ranging from high alpine lakes in the Rockies to desert reservoirs in Idaho, eastern Oregon, and Washington. These insects also hatch on coastal, sea-level ponds and estuaries.

Gulper Special

During a good Callibaetis hatch or spinner fall, proficient anglers may have a dozen or more trout circle in and out of the net. On many of the West's special-regulation stillwaters, fish can average three or four pounds, and a real hog might tip the scales at five pounds or more. You'd be hard-pressed to find that many large fish on a public section of a river or creek.

Callibaetis are multibrooded insects, a fancy way to say they are abundant and on any given summer day you might find a slew of these bugs on the water. However, Callibaetis activity typically spikes early (May and June) and late (August and September) in the season. Be sure to note the size of the Callibaetis you are trying to imitate. As the fishing season progresses, each brood requires less time to mature but is smaller than the previous generation. The #14 pattern you used in the spring is too big to represent the #18 Callibaetis hatching in late summer.

Callibaetis are beautiful, mottled-wing mayflies, typically matched by #14-18 imitations. The duns have two tails, a cream underbody, and a brown or olive back.

In May and June, Callibaetis dun hatches and spinner falls typically happen during warm, late morning and afternoon hours, which allows anglers to live like bankers--you don't have to be on the water until 10:30 or 11 A.M. At this time the insect can be matched by either a #14-16 dun or spinner. Often spinner falls coincide with emergences, so you may find trout feeding simultaneously on both. At other times the fish can key in on one stage of the hatch and anglers must match that preference.

Use A.K.'s Callibaetis Spinner (below) to imitate mayfly spinners lying flush in the surface film.

A.K.'s Callibaetis Spinner

I encountered my most memorable Callibaetis action while fishing Georgetown Lake in southwestern Montana. There wasn't a breath of wind on the water and the sky was mostly overcast, so the big rainbows and even a few brook trout left huge boils on the surface. The entire lake was alive with emerging insects and trout gulping them down like candy. I tied on a length of 6X tippet and a #16 gray Sparkle Dun.

I made a cast and a fish ate. The next cast, same result. During the next half-hour I hooked a dozen or more large rainbows.

This trophy brook trout was caught on Montana's Georgetown Lake during a Callibaetis hatch.

I returned the next day. The bugs came off at 10 A.M. and they continued until 3 P.M. I landed two rainbows over 20 inches, a half-dozen between 13 and 18 inches, and one brook trout that may have weighed 4 pounds. I don't think an angler could have walked away from Georgetown Lake that day feeling anything but giddy. I wondered if all the anglers on the Bitterroot, Big Hole, or nearby Rock Creek--dealing with launch lines, racing to the best riffles, banging their boats off each other and trying to coax fish to salmonfly imitations--felt the same way.

After emerging, duns waste no time drying their wings in the sun and getting airborne, sometimes making them tough targets for rising fish. The best dun fishing occurs on overcast days when emerging Callibaetis ride the surface for extended periods until their wings dry.

Gray CDC Biot Compara-dun

July and August provide quality Callibaetis action, but the midsummer hatch and spinner fall is mostly confined to morning and evening hours when temperatures are cooler. September and even early October may provide decent Callibaetis hatches and spinner falls, especially during the warmest hours. The bugs are still fairly small and can be matched by a #18 imitation.

Matching the Callibaetis Emergence
Callibaetis are not difficult to match and even beginning anglers should be successful when casting a line during a solid emergence or spinner fall.

If you arrive before the hatch, work nymphs over submerged weedbeds where Callibaetis nymphs swim and are most active. Weedy areas and Callibaetis nymphs go hand-in-hand because the nymphs feed on diatoms and algae. They can tolerate high water temperatures so don't overlook weedy, shallow shorelines where water is often warmer.

According to Malcolm Knopp and Robert Cormier, authors of the book Mayflies, Callibaetis nymphs repeatedly swim from submerged weed beds to the surface and back again without pausing just before hatching. By swiftly flipping their tail, Callibaetis nymphs can jettison through the water in quick six-inch bursts. On the final ascent to emerge, they slowly rise through the water and typically do not stop until they reach the surface. This is when trout gluttonously feed because the slow-rising nymphs are easy targets.

Mercer's Poxyback Callibaetis

To imitate swimming nymphs, use a medium-sinking or full-sinking line and Callibaetis nymphs with or without a flashback or a Gold-ribbed Hare's Ear and retrieve it in quick six- to eight-inch strips. Use these tactics to enjoy a half-hour to an hour of productive action before the hatch begins.

If fish don't show interest in the swimming presentation, allow the fly to sink longer and retrieve it at a consistent pace like a nymph making a final ascent to the surface. Don't pause during this retrieve, because it may cause the fish to reject your fly.

When a decent emergence begins, the water's surface will be littered with mayfly shucks and host Callibaetis duns, cripples, and stillborns. Though the most telltale signs of a hatch will be the numerous boils and gulping sounds made by trout sucking down adult Callibaetis.

GULPER CENTRAL Good Callibaetis waters are spread across the West. Some are more noteworthy than others. Here's a look at several Northwest lakes and reservoirs where Callibaetis can be found. The top three stillwaters in each state are marked, but the locations listed after are also productive waters. Remember, this is a thin list when considering Callibaetis options. MONTANA Georgetown Lake Clarks Canyon Reservoir Hebgen Lake Cliff Lake Wade Lake Elk Lake Goose Lake Kipp Lake Duck Lake Mitten Lake Mission Lake WASHINGTON Chopaka Lake Dry Falls Lake Lenice Lake Quail Lake Lenore Lake Pass Lake Lone Lake Omak Lake Twin Lake Nunnally Lake Ell Lake Blue Lake IDAHO Henry's Lake Island Park Reservoir Chesterfield Reservoir Daniels Reservoir Twenty-Four Mile Reservoir Hawkins Reservoir OREGON Grindstone Lakes Chickahominy Reservoir Davis Lake Wickiup Reservoir Klamath Lake Crane Prairie Reservoir East Lake Gold Lake Lost Lake

The most effective way to catch trout during a Callibaetis emergence or spinner fall is to apply the old duck hunter's rule of thumb--don't flock shoot. In other words, don't cast blindly; target your fish. Watch for fish that repeatedly rise every few feet. Try to determine the direction the fish is traveling and maneuver so the fish crosses within casting range. Then place your fly in its path, wherever you think the next rise will occur.

It's important to be stealthy when fishing gulpers. Try to minimize surface disturbances created by your boat or float tube, or your legs if wading. A fish may not spook from ripples and small waves, but they may change their course to somewhere outside casting range.

To match Callibaetis emergers and duns riding on the surface use a Callibaetis Cripple, Callibaetis Sparkle Dun, Gulper Special, Bivisible Dun, or a Stalcup CDC Biot Compara-dun. Light Cahill and Parachute Adams patterns also work well. You'll garner more attention using 6X on a calm day when the surface is flat, but you'll pay for it when a large fish snaps your tippet like sun-bleached sewing thread. On windy days, when a surface chop is present, 5X works fine.

If you are having trouble finding an effective pattern or retrieve, don't fret. Voices carry vast distances on lakes and reservoirs and anglers are terrible at keeping their mouths shut. Give it a few moments and you will know exactly what pattern, what type of retrieve, and at what depth other anglers found success.

Matching the Callibaetis Spinner Fall
Callibaetis spinner falls occur at all times of the day. Early and late in the season spinner falls generally happen in the afternoon as air temperatures rise. During the hot midseason spinner falls are mostly restricted to cool mornings and evenings.

Callibaetis spinners are easily identified. Look for mayflies dancing near the banks, especially around brush, in quick, vertical two- or three-foot rises and drops. Fertilized females seek cover along the shorelines and rest for a few days until they are ready to deposit their eggs in the water. When the eggs are mature, the females begin depositing them in the water, usually in midafternoon, releasing somewhere between 400 to 500 eggs. They hatch almost immediately and begin feeding. Within six weeks, a nymph may harbor developed wing pads and be ready to emerge.

Callibaetis spinners are gray with two tails and clear wings accentuated by black patches. Because of their mottled wings, they are sometimes called speckled-wing mayflies.

During spinner falls, which are most pronounced near shoreline areas adjacent to weed beds, opt for a specific spinner pattern such as A. K.'s Quill-body Callibaetis Spinner or a CDC Biot Callibaetis Spinner.

The term "gulper" originated on Hebgen Lake (above) and refers to the sound the trout make when they feast on Callibaetis. When gulper fishing, don't flock shoot. Target your fish and cast where you think it will rise next. A cast into the ring of the last rise is the worst place for your fly to land.

While Callibaetis mayflies aren't about to take over top spring billing from the big-name hatches on rivers and streams, they do provide a great option for stillwater anglers who desire a predictable day and several large trout in the net for their efforts. Callibaetis hatches aren't difficult to match and they can bail you out when the West's rivers and streams run frighteningly high or late-summer bone-dry. Really, in a world of fleeting, hit-and-miss hatches the Callibaetis is refreshing--it's a beautiful bug that both you and the trout can count on.