As the weather begins to warm on western Montana rivers, fly anglers get excited for early-season hatches of large stoneflies. The Skwala stonefly hatch is neither a prolific nor widespread hatch; there can be some significant hatches on Montana's Bitterroot and Clark Fork Rivers. The problem is the hatch is far more erratic than most, both in timing and duration. Water temperature is a key factor in the emergence. The Skwala nymph becomes fairly active at around 38-40 degrees and the adults will generally hatch anywhere from 42-47 degrees. The nymph generally emerges in the late afternoon and into the evening.
The Skwala stonefly is similar to a salmonfly (Pteronarcys californica) in appearance and habitat but is from a different biological family. The Skwala is kin of the little yellow stoneflies. Slightly smaller than a salmonfly and more drab in color, the Skwala hatch in western Montana as early as March. Much like other large stoneflies, the Skwala emerges by crawling to shore, and then rests on rocks or vegetation until returning to lay eggs. This size 8-10 stonefly sets the motion for great spring time dry fly fishing.
More about Skwala:
Order – Plecoptera, Family – Perlodidae, Sub Family – Perlodinae, Genus - Skwala Curvata and Americana or Parellela
Nymph Characteristics:
Body length - 1/2" (abdomen and thorax), with antenna and tail – 1 1/4"
Tail length - relatively long 1/2"
Color- tan to olive dunAdult Characteristics:
Body length - 1/2" (abdomen and thorax), with antenna and tail – 1 1/4"
Tail length - relatively long- 1/2"
Color - dirty yellow to bright yellow to dark/olive-black
The Skwala is a typical stonefly in that it prefers faster, oxygenated water. Also the life cycle is one year and it survives as a predator by eating other aquatic insects.
The Skwala is an important food source for trout in a few stages. In the active nymph stage it is often found in the water/food column for trout, being knocked loose and drifting freely. This is especially true during pre-hatch periods when its movement activity increases dramatically. Skwala also become available to trout as the female adult returns to the water to lay eggs. On windy days, adult Skwala are blown from plant material on banks into the water; or as a spent adult, it will typically fall on the water to die.
The Skwala stonefly can be found in California, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, Utah, Washington, and Wyoming.
Other hatches and important food sources for early spring are Blue Winged Olive, March Brown and Ameletus or Brown dun.
For more info: see the links below
Montana Fish, Wildlife and Parks – Fishing information
Wapiti Waters Fly Fishing Montana – Seasonal hatch primer for western Montana and more fishing information
Fly fishing blog – in western Montana
Westfly Entomology – for the western fly fishing community
Merle’s SmugMug photo site – More river and fishing photos in their original format/resolution. Incudes skwala photos, fish, river shots from the early season.
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