A Tale of Two Skwalas

It’s March 1st. Quarter-size wet snowflakes mix with sleet. On the icy wind, a buzz is building across the frozen landscape, faint at first but growing louder and louder. There it is again. Listen carefully. Can you hear it? “The Skwalas are coming.” These four words, like Beethoven’s 9th, are sweet music indeed to the ears of cooped-up fly fishers suffering from winter’s melancholia.

On the surface, the early season Skwala hatch on Western rivers has all the elements of a juicy Hammett mystery—anticipation, uncertainty, and elusiveness. The plot develops something like this: Cast size 8 and 10 dry flies to wild rainbows and browns hungry as hostages after a winter diet of pinhead-size midges. Brave wind, snow, and rain. Freeze your butt. Pray for a warming weather front. Ignore the caustic remarks from the uninitiated: “Dry-fly fishing in March, are you nuts?” “Where are the rising fish? It’s still winter for crying out loud.”

Only in the last two decades or so has the Skwala stonefly been identified by entomologists as a different species than its distant cousin the Golden Stone. “Skwala stoneflies are among those rare aquatic insects so little known, or its importance so recently noticed, that it goes by its Latin genus name rather than a raft of confusing common names,” notes renowned fly fisher and writer Dave Hughes.

This new revelation has uncorked a frenzy of fly fishers pursuing trout with nymphs and large dry flies in late winter and early spring on several Western rivers from the Rocky Mountains to the coastal Cascades and high Sierra of Northern California. However, for the majority of fly fishers still unfamiliar with the Skwala hatch, the notion of casting big dry flies to hungry trout amid frequent whiteouts, rainstorms, and blustering winds still sounds like a fishy tale.

To help raise awareness of the Skwala phenomenon, I have given more mention to two rivers that produce abundant Skwala hatches—the Yakima, in eastern Washington State and the Bitterroot in southwest Montana. Both of these systems share enough commonalities that they characterize the Skwala hatches of several other Western rivers where they are also important. But before getting too far upstream, a touch of history is in order.

Family Matters

The story of the Skwala stonefly begins in prehistoric times long before humans walked out of Africa to colonize the world some 80,000 years ago. Changing little in appearance over millennia, these primitive aquatic insects have sometimes been mistakenly identified as Salmonflies, Golden Stones, and Yellow Sallies.

Sometimes referred to as short-winged Spring Flies, Skwalas belong to the Plecoptera family. Skwalas are a big clan with over 30 families and 121 species and are linked to some surprising relatives. “The Skwala nymph features three distinct thoracic segments giving them an armor plated appearance just like their distant cousin the cockroach,” notes writer Philip Rowley, in Fly Craft Angling.

Skwalas are further classified within subfamilies, Perlodidae and Isoperlinae. In terms of territory, the Isoperlinae family is scattered from Atlantic Canada and Minnesota south to Mississippi and South Carolina. Sparser populations result in less interest by trout and by anglers. In the West, where the Perlodidae family rules, it’s a different story. Two species similar in size, shape and color, Skwala americana and the less common Skwala curvata, occur only in Western streams.

Eat or be Eaten

Skwalas are predators. Adult females are 1½" not including antennae and tail, versus 1" to 1¼" body length for males. Females are voracious, carnivorous, eating machines. Needing protein to feed the egg clusters that will eventually grow within the black tear-shaped sac that extends off the tip of the abdomen, female Skwalas constantly snack on aquatic organisms like mayfly nymphs and midge larvae. Could this account for declining mayfly hatches in streams with large Skwala populations? “It’s a possible theory that has been raised but can’t be proven without further scientific study,” notes John Banks, Ph.D., who teaches graduate-level courses in biology, entomology, and ecology at the University of Washington’s Tacoma Campus.

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One fact is established. Whether it’s the Yakima, Bitterroot, Clark Fork, Big Hole, Deschutes, McKenzie, Owyhee, or Yuba rivers where Skwalas thrive, water temperatures trigger the hatch. “The nymphs get active and start migrating when water temperatures reach 38 to 40 degrees F. The adults hatch when water temperatures rise into the mid to upper 40s,” says Steve Joyce, co-owner of Red’s Fly Shop on the banks of the Yakima River in eastern Washington.

After a long cold winter, trout are tired of eating small mayflies and aquatic larvae. The sight of an inch-long Skwala nymph can get the their attention the way a dying salmon does a hungry grizzly. The fish are also moving into a prespawn mode that raises both their hunger level and their metabolism as the water temperatures warm.

Like all stoneflies, male Skwala nymphs lead the migration from midstream to the river’s edge. Skwalas are clingers and crawlers and as a result are lousy swimmers. They are easy targets for trout if they lose their grip and begin to drift.

“This is a key time to get your nymphs down so they drift just off the bottom,” says Joyce. “Fishing a two-fly indicator system is your best setup. Your top bug could be a Pat’s Stone, Jimmy Legs, or Kaufmann’s Stone in a size 10. Your bottom nymph should more closely imitate the Skwala nymph,” adds Joyce.

The Yakima has one of the earliest Skwala hatches compared to rivers like the Bitterroot in southwest Montana,  500 miles to the east. In mid-February, with daytime temperatures averaging 42 degrees F. and water temperatures hovering around 37, the Skwala emergence begins. Conversely, Bitterroot Skwalas start migrating three to four weeks later in March because of much colder air and water temperatures. “Each year anglers keep trying to fish the hatch earlier and earlier, with little success,” says Brandon Boedecker, owner/outfitter of Montana-based Pro Outfitters. “Its kind of like advertising Christmas in July.”

A Year to Remember

In the spring of 2012, the Skwala hatch exploded on the Yakima. From top to bottom, there were reports of Skwalas on the water and crawling all over the banks.

“I’ve never seen anything like it in 15 years of guiding,” said Johnny Boitano, co-owner of Troutwater Fly Shop in Ellensburg, Washington.

I can back up Boitano. I was fishing with Steve Joyce in the Yakima Canyon, and we saw several days of the same phenomenon. Battalions of Skwala adults would suddenly appear floating down the river, anywhere from noon to 2 P.M., with fish rising to smash the bugs with violent strikes.

It’s difficult to judge if the Skwala hatch on the Yakima was an anomaly. Prior to 2012, three years of record high water during March and April made the river unfishable. However, if the right conditions converge in 2013—such as stable flows and mild temperatures—it could be déjà vu.

A more typical Skwala emergence is what occurred on the Bitterroot in the spring of 2012: “The problem is our spring weather makes the hatch hard to predict both in timing and duration,” says Boedecker. “It’s kind of like Bigfoot. You hardly see Skwalas on the water, or shucks on the rocks, or adults flying around like Salmonflies or Goldens, so anglers wonder if there really is a hatch.”

Of all Western rivers, the Bitterroot is best known for its Skwalas, and every year triggers a spring pilgrimage of fly fishers. “Word spread about 10 years ago,” says Sean O’Brien, owner/outfitter of Osprey Outfitters, in Hamilton, Montana. The Bitterroot’s habitat is the perfect incubator for stoneflies and other aquatic life. Fast-flowing, riffled, well-aerated cold water with large to medium cobbled rock bottoms is ideal stonefly habitat.

Unlike the Yakima River’s miles of steep, shadowed basalt cliffs, the expansive, sun-exposed flatlands of the Bitterroot Valley are wide open and level. “We call it the banana belt of Montana,” says O’Brien.

The Bitterroot Valley floor has tremendous solar access and as a result is an incubator for aquatic life. Turns out in the case of the Skwala hatch, abundant sunshine is a friend, not a foe. Unlike summer rays that often put trout down, sunny days in late winter and early spring warm the water temperatures that fuel the hatch.

Two other rivers with notable Skwala hatches, the Yuba in northern California and the Deschutes in southern Oregon, experience daytime highs in the 50s and 60s in January and February.

As a result, knowledgeable local fly fishers start nymphing the Skwala hatch as early as January, and cast dry-fly imitations in mid-February.

Hear the Drumbeat of the Skwalas

As more and more Skwalas reach the river’s edge, the males hunker down preparing for the arrival of the females, which could be in a few weeks, here again depending on water temperatures.

Once the female nymphs follow the males into shallow water, the reproductive process begins. But how do they find each other?

“Stoneflies locate each other through drumming vibrations. The males thump rocks with their abdomens and the female follows the sounds,” explains Banks. So do trout feel the drumbeat? Science says yes. “Underwater sound has probably been used by marine animals for millions of years,” says Banks. The science of underwater acoustics began in 1490 when Leonardo Da Vinci wrote, “If you cause your ship to stop and place the head of a long tube in the water and place the extremity to your ear, you will hear ships at a great distance from you.”

Think about that the next time you wade willy-nilly into a run or slap your oar in the water or carelessly drop your anchor. There’s really no need to announce your arrival.

The female adults return to the river to lay their eggs. Even though they have wings, females are often reluctant to use them. Rather they skitter across the water’s surface depositing their precious egg cargo. Once her egg mass separates and falls to the stream bottom, the cycle is renewed.

Back on the bank, the males spend their days roaming around looking to mate with more females. They never fly. Their wings are only about half as long as their abdomens, and too small to take flight. This is an anatomical condition called “brachyptery” or short, nonfunctional wings. It occurs in many stoneflies.

“Early in the adult hatch, when water temperatures rise above 45 degrees F., many fly fishers prefer bushy patterns like Stimulators or Chubby Chernobyls to simulate the female skittering across the surface to lay her eggs,” says Joyce. He also says that as the hatch progresses, it’s important for your dry fly to ride low in the surface film. That’s because Skwala wings lie flat along their backs while at rest.

The egg-laying flights of the females don’t begin until the temperatures are warm enough for them to take flight—this is usually early afternoon. Casting a dry fly alongside the willows and shoreline during the warmest part of the day can produce explosive strikes.

Because trout see females almost exclusively, adding a small piece of black foam, which represents the egg sack, to the tip of the abdomen, makes a lot of sense. Trina’s Dog Puke (Skwala) and many other patterns include an egg sac as part of the adult Skwala imitation.

Does Skwala Color Matter?

Substantial research shows why color matters. Read Trout Tactics by Dave Hughes or Color Vision in Trout and Salmon by Gary Borger, and you will see how color plays a pivotal role in fly fishing.

At first blush, the untrained eye might see few color differences between Skwalas in the Yakima and those in the Bitterroot. However, habitat, water temperatures, and the timing of the hatch can affect the color and size of Skwalas.

For example, the Rocky Mountain Skwala found in the Bitterroot is olive and dark brown. The adults have dark smoky-colored brown wings, and brown legs, and olive highlights on their abdomens. The males are usually smaller and generally darker in color than the females.

Skwalas on the Yakima River, however, tend to have more dirty yellow abdomens with a slight tinge of olive. In the higher reaches of the river, closer to the Cascade Range, male adult Skwalas are noticeably smaller and darker. Higher elevation, colder water temperatures, and a later emergence are thought to be the reasons for the difference in size and color, but diet and the color of the river substrate also play a huge role.

Farther south, in the Deschutes, Willamette, McKenzie, and the Yuba in northern California, female Skwalas have paler wings, and olive abdomens tinged with primrose. The males are usually smaller and darker, with yellow and dark brown variegated abdomens.

To the west, in the Big Hole River Valley, yet another subtle difference occurs in the adult. “Very dark olive bodies that almost look black,” says Eric Thorson, co-owner of the Sunrise Fly Shop in Melrose, Montana.

The Big Hole Valley is one of the coldest zones in the continental U.S., and as a result, it also has one the latest Skwala hatches in the West. “We get the bugs for about three weeks with excellent dry-fly fishing in May. The problem is that hardly any anglers show up to fish it,” adds Thorson.

Despite the lack of attention on the Big Hole, there’s no question that news of the early season Skwala hatch is emerging faster than a rising river. Google “Skwala” and an army of websites and YouTube videos pops up. In addition, guide chatter fills cyberspace with real-time reports via everything from Facebook to Twitter. Photos of big fish in hand or in the net are downloaded instantaneously from smart phones and posted on the Internet.

Is the Skwala hatch as biologically important as the big bugs that come later like Golden Stones, Salmonflies, or Green Drakes? Probably not. But to the pysche of a fly fisher, they may be even more important, or at least more exciting, because when you hear “the Skwalas are coming,” you know also that a long winter is finally over, and good fishing is on the horizon.

Three Skwala Fly Recipes

Thurman's  Thurminator Stone

HOOK: #10 Montana Fly Company 7073.
BEAD: Black Tung Bead, #2.
WEIGHT: Lead wire, 1 mm.
THREAD: Olive 6/0 UNI-Thread.
TAILS/ANTENNAE: Olive Nymo Thread. 
BODY: Olive 6/0 UNI-Thread.
RIB: Black #1 wire.
HACKLE: Olive organza.
LEGS: Olive Super Floss.
WINGCASE: Olive UV Frog’s Hair under brown raffia.
COLLAR: Olive UV Frog’s Hair.

Clook's "Floater in the Pool"

HOOK: #8-12 MFC 7073 or Daiichi 1730 with bent shank.
THREAD: Olive 6/0 UNI-Thread.
TAILS: Pearl Flashabou Accent.
RIB: Brown 60-pound-test nylon monofilament.
BODY: Olive Antron dubbing.
WINGCASE: Brown 3 mm closed-cell foam.
THORAX: Pale yellow Wabbit Dubbing.
UNDERWING: Pearl Flashabou Accent.
WINGS: Cow elk flank.
LEGS: Centipede Legs, #1, black.
INDICATOR: Yellow 3 mm closed-cell foam.

Trina's Dog Puke (Skwala)

HOOK: #10-12 MFC 7026 or Tiemco 5262.
THREAD: Olive 6/0 UNI-Thread.
TAIL: Brown goose biot.
EGG SAC: MFC X-Body, medium #2 Skwala.
BODY: Mottled yellow Skinny Skin.
LEGS: Brown Super Floss.
THORAX: Light olive Frog’s Hair.
UNDERWING: Dark dun Medallion Sheeting.
WING: Cow elk flank.
THORAX: Skwala UV Frog’s Hair.

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Michael Hamilton is a former broadcast journalist. His awards include Associated Press and United Press International Reporter of the Year, he was nominated for two television Emmy Awards, and received three Edward R. Murrow Awards for Excellence in Broadcasting. He has been writing outdoor and travel freelance articles for a decade.