Callibaetis is the mayfly of lakes. Twenty-nine of the 31 lake pages on this site list it, and the two that don't, Pyramid and Walker, are alkaline desert lakes without the weed beds the nymph needs. It is a member of the Baetidae, the same family as the river blue-winged olive, and it lives the way its river cousins do: a fast-swimming nymph, a quick emergence, and a spinner fall you can set your watch by. What makes it different is where it lives. Callibaetis nymphs need still or barely moving water with submerged vegetation, so they are a stillwater insect first and only turn up in rivers where the water is slow and weedy enough to behave like a lake.
The speckled wing and how to recognize it
The adult is a medium-sized mayfly, a size 12 to 16, with a gray or tan body and a distinctive mottled pattern on the wings that gives it the common name "speckled dun" or "speckled-wing quill." The male spinner has clear wings with a dark leading edge; the female spinner keeps the speckling. Duns sit upright on the surface with wings folded like a sail. Nymphs are slender, olive to tan, with three tails and a habit of darting in short bursts and then pausing, which is the exact motion a strip-and-pause retrieve copies.
One thing sets Callibaetis apart from most mayflies: there are several broods a season. The first hatch after ice-out produces the biggest insects, a true size 12 or 14, and each following brood is a little smaller, so by late summer you are matching a size 16. If your size 14 Sparkle Dun is getting refused in August, go down a size before you change patterns.
The nymph is the meal
Trout in a Callibaetis lake eat nymphs all day, every day, for the whole season, and eat duns and spinners only when the surface fishing is on. The nymph lives in and around weed beds in water from a few feet deep down to whatever depth light still reaches the plants. Fish it there: over the tops of the weeds, along the edges where a weed bed drops off into open water, and across the shallow shelves early and late in the day.
The Callibaetis Nymph in 12 through 16 is on every lake page that lists the insect, from Crowley to Hebgen to Eleven Mile. A Pheasant Tail or Hare's Ear in the same size does the same job. Fish it on a floating or intermediate line with a long leader, count it down to the weed tops, and retrieve in short strips with a pause between them. The take usually comes on the pause. In the hour before a hatch, the nymphs get restless and swim toward the surface, and a nymph fished just under the film with a slow lift catches the fish that are chasing them.
Emergence: late morning, calm water
Callibaetis hatch in the middle of the day, typically from late morning into early afternoon, and the best hatches happen on calm, warm mornings. Wind that puts a chop on the water delays the hatch and scatters the duns. The nymph swims to the surface, splits its shuck in the film, and the dun rides for a while before flying off to the shoreline brush. Trout cruise the surface during the hatch, taking a dun or emerger every few feet, and the game is to read the direction a fish is moving and put the fly two or three feet ahead of it. A Sparkle Dun in 12 to 16, which is the dry listed on nearly every lake here, sits low with a trailing shuck and imitates the emerging insect and the dun at the same time. The CDC Callibaetis and CDC Callibaetis Emerger on the Strawberry, Almanor, Diamond, and Pass Lake pages ride lower still, for fish that ignore the dun and take only the cripples.
The spinner fall
Duns molt into spinners in the shoreline vegetation and return to the water to mate and lay eggs, usually the next morning, often around the same late-morning window as the hatch. On a good day the spinner fall and the hatch overlap, and trout may be taking both. The spent spinner lies flat in the film with wings out, and fish take them with a quiet sip that is easy to miss. A spent-wing Callibaetis spinner in the same size, or a Sparkle Dun trimmed flat, is the fly. Cast to cruising fish exactly as you would during the hatch.
Where and when on the lakes here
The peak months in the lake matrices line up almost perfectly with elevation and ice-out:
- June through August on the mid-elevation lakes: Crowley, Bear Lake, Blue Mesa, Eleven Mile, Eagle Nest, Heron, Flaming Gorge, Flathead, Chelan, Pend Oreille, Pass Lake, and Woods Canyon.
- June through September on the rich, weedy lakes that hold a hatch longest: Strawberry, Almanor, Diamond, Crane Prairie, and Spinney Mountain.
- July through September on the colder or higher lakes: Hebgen, Henry's Lake, Georgetown, Fish Lake, Convict, and Odell. Jackson Lake and Scofield narrow it to July and August.
- August and September only on the latest-thawing lakes: Fremont, Redfish, and Yellowstone Lake.
- May and October on Eagle Lake, whose summer water gets too warm for the fishing to matter.
The same insect does show up on three river pages, Silver Creek, the Henry's Fork, and the Metolius, all of them spring creeks with slow, weedy water. The fish behave like lake fish on those hatches, cruising and sipping, and the same flies work.
Setting up for a Callibaetis morning
- Get on the water early and fish the nymph over weed beds until you see the first duns.
- Carry two rods if you can: one rigged with the nymph on an intermediate line, one with a Sparkle Dun on a floating line and a 12-foot 5X leader.
- Anchor or kick to a spot that puts the sun behind you and lets you see cruising fish on the flats.
- Lead moving fish. A cast that lands on a cruiser's head spooks it; a cast three feet ahead gets eaten.
- Drop a size when refusals start. Late-season Callibaetis are a full hook size smaller than the June bugs.
Boat and motor rules vary lake to lake, and several of these waters are inside national parks, so check the managing agency before launching.