Stonefly nymphs of many species are available on the Yakima year-round. The Skwala nymphs begin to become more active when water temperatures reach the upper thirties and become particularly vulnerable when they begin to crawl toward shore. This can occur as early as late January or February. One of the best-looking Skwala nymph imitations I've seen is Pat's Rubberlegs; its mottled olive-and-black chenille body reproduces the colors of the natural particularly well.

The best thing about the Skwala is that the adults begin to emerge, sometimes as early as mid-February, and continue to do so into April. This coincides with the pre-runoff period when flows are still low and the water is clear; they can provide excellent dry fly fishing throughout that period. I've written an article on Skwalas and Skwala fishing that will be published in the spring issue of Flyfishing & Tying Journal.