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From now into early March is the heart of winter in the Rocky Mountain region. With the exception of those few hardy souls who accept the challenge of fishing in the cold and snow, many anglers use this downtime to tie flies and plan for the upcoming fishing season. I’ve found the best way to begin planning is to pinpoint the timing of key insect hatches.

In this column, I’ll take a look at the first major hatch, the Skwala stonefly, which is probably your best bet for getting an early start on stream fishing in the West. Locals and a growing number of visitors target the Skwala hatch on Montana’s Bitterroot and Clark Fork rivers as their fishing season’s kickoff event.

The Skwalas do their thing in early spring, prior to run-off. The hatch usually begins in late February as winter fades and stream temperatures rise to a minimum of 45 degrees. Depending on weather, of course, eager anglers usually begin their assault the first week of March. The hatch peaks around the first two weeks of April. By May, the Skwala fishing is finished.

Like the larger and better known Salmonfly, the Skwala is a stonefly. The Skwala averages about one inch long, the body is usually dark brown or olive and sometimes black. Only the females have wings. When not in flight a Skwala’s wings extend the length of the body.

Because the stonefly’s life cycle passes through only two stages, the nymph stage and the adult stage, and because of their comparatively large size, stonefly hatches are simple to fish in comparison, for instance, to midges and mayflies. The stonefly’s large size makes the imitations easy for the angler to follow on the water.

Over the years, local fly tiers have developed many Skwala imitations. Fly shops and guides can tell you what’s working. Personally, I’ve found a floating size 10 or 12 green-bodied Stimulator works as well as anything. If you’re into nymphing, a stonefly nymph or Hare’s Ear fished just off the bottom works well. Some anglers go both ways, using a dry imitation on top in tandem with a nymph imitation beneath.

Despite the relatively large size of the Skwala, they are not showy emergers. You may not even see one while fishing, but they are there and the trout know it.

Typically, a fishing guide will float you about 20 to 30 yards off the shoreline and have you cast toward the riverbanks. Don’t expect a 20-fish day; four or five trout is a good day. But the browns and rainbows will likely be in the 14- to 18-inch range – nice fish.

The Bitterroot is prime Skwala water for visiting anglers. Two of my sons live near the Bitterroot, and both have fishing rafts, so I’ve fished the Skwala hatch here many times. Access is easy. The east and west forks of the Bitterroot come together a few miles south of the town of Darby to form the main river. Highway 90 parallels the “Root” for its entire length, about 70 miles, with many public access points along the way. The towns of Hamilton, Stevensville, Florence, and Lolo offer full services. The river feeds into the Clark Fork a couple miles west of Missoula.

Weather is critical in fishing the Skwala hatch. Late winter/early spring in Montana often brings quick changes of weather which can turn an otherwise uneventful float into, for lack of a better word, an adventure. When my son and I launched this past spring, for example, the weather was wonderful – no wind and not a cloud in the sky. Less than two hours into the float we had a staunch wind blowing into our faces and snowflakes plastered onto our clothing. Getting to our takeout required some strenuous rowing against the wind for over an hour. But before the squall hit we caught a few nice rainbows and a 16-inch brown, so the hardships were worth the hassle (easy for me to say, my son was rowing). The lesson here: Dress in layers and always be prepared for cold weather when fishing in the Rocky Mountain region in early spring.

Though the Bitterroot has become the most popular stream to fish this hatch, local anglers and guides know that the larger Clark Fork River also has a Skwala hatch. Spend a couple of days in the Missoula area and you can fish both streams. If the Skwala hatch doesn’t produce, fishermen have another option: mayflies. Blue Wing Olives begin coming off as early as late February, with peak hatches in April and May. Hungry trout eagerly rise to the occasion after a winter of inactivity. This occurrence of bug-meets-fish is widespread, from small creeks to large rivers, in most western states. Two other spring hatches, the Pale Morning Dun (PMD) and Western March Brown (WMB) provide similar options.

Mayfly hatches produce two fishable stages. First, the bottom-dwelling nymph (best imitated by a small, size 16-22, Pheasant Tail or Hare’s Ear) swims to the surface. During this stage, watch for trout flashing near the river bottom, or tailing just under the surface for the emerging nymphs. This typically occurs mid-morning.

Stage two has the recently emerged mayfly, now known as a dun, fluttering above the stream or riverbank, or floating on the water as they lay their eggs. The Blue Wing Olive resembles a mini pup-tent while riding the waves downstream. You’ll often see trout snouts breaking the surface as they feed. This dry-fly action normally takes place from mid-morning until late afternoon.

The adult Blue Wing Olives, Pale Morning Duns and Western March Browns are small, measuring three-quarters of an inch or less. Small flies and light tippets (6x) are in order. A drag-free drift is essential. These spring mayfly hatches don’t draw hordes of fishermen to western rivers and streams. But they can be a productive backup when the larger stoneflies fail.

Now is the time to make arrangements to fish the Skwala hatch. Here are a few guide services in Missoula and Bitterroot Valley: In Florence, try River Otter Flyshop & Outfitters. In Hamilton, The Flyfishing Center. Missoula has The Kingfisher, and Grizzly Hackle.

In next month’s column, I’ll take a look at the West’s biggest angling event, the salmonfly hatch, plus a few other key hatches that take place in summer and fall.

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