Western Spring Skwalas on the Bitterroot River

Fishing Montana's Bitterroot River during the spring Skwala (Skwala parallela) hatch is one of the West's greatest fly-fishing events. Yes, there are opportunities during summer to catch more and larger trout, but that isn't the point. The Bitterroot, which flows through one of the West's prettiest valleys, offers ample opportunity to catch wild trout on bushy dry flies during a time of year when the Rocky Mountain states are just shaking free from winter weather and the refreshing breath of spring is in the air.

The spring scent and the Skwala hatch offer an indication of what's to come. They revive our spirits and tell us that the worst winter days are behind, and that spring, summer, and fall–with all the angling possibilities they hold–are directly ahead.

Other Montana streams, such as the lower Clark Fork and Rock Creek, offer similar early-season Skwala opportunities, but they don't have as many bugs as the Bitterroot.

I do not regard the Bitterroot as a trophy-trout stream, and it isn't a trout factory like the Missouri or Bighorn rivers, where you can find from 5,000 to 6,000 trout per mile. Several hundred trout, at best, fin in each mile of the Bitterroot, and the big fish are few and far between. Don't get me wrong, the Bitterroot has 5-pound rainbows and browns, and anglers catch them on occasion, but you shouldn't expect to land one. Instead, count on lots of solid, well-proportioned fish in the 15- to 18-inch rang–including native westslope cutthroat. There is no better time to catch the river's largest fish on the surface than during the Skwala stonefly hatch.

Skwala Emergence

The Skwala hatch begins as early as late February and often continues through April. The hatch peaks between the last week of March and the third week of April, especially on warm spring days.

Skwalas are meaty, olive-brown insects. They live among the bottom rocks for a year before various signals, including water temperature and flow, tell them it's time to mate. Typically,the Skwalas crawl from the bottom to bankside vegetation, rocks, and bridge abutments when the water temperature reaches 50 degrees F. Once out of the water, they mate and the females take flight and hover over the river, dunking their fannies in the water, depositing eggs with each touchdown. The males are wingless, an anomaly among stoneflies.

In small to medium rivers like the Bitterroot and Rock Creek, Skwalas can turn up on the water almost anywhere, but it pays to concentrate your efforts on brushy banks with good holding water nearby. Other productive spots include below riffles and large rocks.

The lower Bitterroot near Missoula sees the first Skwalas as early as late February, but the hatch really kicks in around late March or early April as it progresses upstream. When weather and water conditions are consistent, the hatch moves upstream about four miles a day.

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Even during the hatch's peak, don't expect to see many bugs in the air or squadrons of Skwalas flying upriver, as you would expect of salmonflies during a prime Rocky Mountain salmonfly hatch. It's not that kind of spectacle. Instead, look for Skwalas wiggling across the surface, crawling up your waders, or negotiating shoreline boulders. If you turn over a submerged rock, you'll likely find several Skwala nymphs clinging to it. Don't be disappointed if you only find a few Skwalas. The Bitterroot's trout know the bugs are there and eagerly take the naturals, plus a variety of imitations.

Skwala Imitations and Tactics

Chuck Stranahan, who ran Chuck Stranahan's Flies and Guides in Hamilton, created Stranahan's Bitterroot Olive Stonefly (sometimes called the Riverbend Olive Stone) to fish the Skwala hatch. The dry fly's grizzly hackle and bulky elk-hair wing make it extremely buoyant, which allows you to hang a nymph dropper off the hook eye. The fly has a bullet head and hackles that are clipped underneath to make it ride low in the water like a female natural.

John Foust, a noted Bitterroot Valley fly tier and a veteran Montana guide, says bullet-head and Chernobyl-style flies are the way to go.

"There are two major parts to a good adult Skwala pattern," Foust says. "You need a wing that spreads out just like the natural and you need an egg sac. A bullet-head Skwala with an egg sac is an exceptional pattern. Really, it comes down to fishing a bullet-head or a Chernobyl Skwala. They both can support a dropper—the best technique for the Bitterroot."

Adult Skwalas measure about a half-inch to one inch long and are matched with #8 and #10 patterns fished dead-drift. Because the air is cold when they emerge, the naturals don't skitter on the surface like other stoneflies later in the season.

Nymph patterns, such as a rubber-leg brown stone and a peacock-body stone tied on #10 and #12 hooks, also work well. I've taken as many fish with nymphs as I have with drys.

You can catch more fish if you drop a small (#14-#18) bead-head Pheasant-tail Nymph off an adult Skwala dry. The small nymph matches Baetis and March Brown (Rhithrogena morrisoni) mayflies, which the trout eat, although they are not tremendously important on the Bitterroot. Occasionally the March Browns come off heavy for a couple hours in the afternoon, and a #16 Parachute Adams, gray or brown Sparkle Dun, or March Brown Cripple takes fish.

Skwala Fishing Equipment and Conditions

Nine-foot, 4- and 5-weight, medium- to fast-action fly rods are ideal for fishing the Skwala hatch, because they have the power to punch casts across the Bitterroot's wide stretches and hit bankside pockets quickly. I use 9-foot leaders tapered to from 3X to 5X, depending on water clarity (use thinner tippets in clearer water). For the nymph dropper, I attach 12 to 18 inches of 5X tippet to the dry's hook eye and put split-shot or Twist-On lead a few inches above the nymph to sink it to bottom.

Quick action is not the norm during Skwala hatches on the Bitterroot or other streams. You can catch many good fish in an afternoon, but your catch rate will depend on the weather and water conditions. During March and April in Montana, that's a crapshoot. For example, a few hot days will melt snow in the high country and flood the Bitterroot's tributaries. This clouds the mainstem Bitterroot and usually turns off the fishing. The same thing occurs when western Montana has a week of rain or snow, as it often does in spring.

During high-water conditions, the Bitterroot is no place for novice oarsmen. The river destroys rafts and boats each year, and it occasionally kills. It twists and turns, especially in its upper portions above Stevensville, which forces oarsmen to make quick decisions. Despite the high-water dangers, the Bitterroot has many exceptional floats. Here are a few of my favorites: Hannon Memorial to Darby Bridge (4 miles) or Wally Crawford (11 miles); Angler's Roost to Silver Bridge (7 miles, watch out for the diversion dam); Silver Bridge to Woodside Crossing (4 miles); Victor Crossing to Stevensville (9 miles); Lolo to Fort Missoula (both unimproved accesses; about 8 miles).

Excellent wade-fishing is available throughout the river system when the river's flow is 1,200 cfs or less. You can find decent wade fishing options whenever the river is below 1,500 cfs. The river is best fished from a boat when it is between 1,400 and 2,000 cfs. For up-to-date flow rates on the Bitterroot and other rivers, log on to https://waterdata.usgs.gov/nwis/rt. Choose the Montana section and then the link for "Bitterroot R. nr Darby" gauging station.

If you encounter dirty water when you visit the Bitterroot, don't fret. A few days of cool weather will cause the river to clear, and when it does, the fishing really turns on. During prime conditions, it's not uncommon to hook a dozen or more trout in a long afternoon. I landed about 15 solid fish during my best day fishing Skwalas. One year, I netted and released a fat 21-inch rainbow that I took on a Skwala dry.

If you live near the Bitterroot, hit it when conditions are prime. If you fly or drive long distance to reach it, plan to spend from 7 to 10 days on the water so you can experience at least some decent water conditions. But remember, the later you fish in April, the more likely you will see the river blown out.

The Skwala hatch is not a well-kept secret and the river is often crowded during the best weather, but the Bitterroot Valley endures enough marginal days–when Mother Nature spits wind-driven hail, rain, or snow–that ensure solitude. If you are willing to battle the elements, catching big trout on large dry flies with a measure of solitude is possible.

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Greg Thomas is the former Western Field Editor for Fly Fisherman magazine.