Western fly anglers often go ga-ga over salmonflies, and for good reason. The nymphs are huge--sometimes constituting the largest non-fish biomass in the river. Adults arrive at the onset of summer when fishing is as pleasant as it's going to get.
Nymphs are large and live in riffles and rocky, bouldery areas with moderate to fast current. They often lose their grip and are taken all year by trout. An appropriate pattern dead-drifted near the bottom is effective.
After three years in the water, the mature nymphs crawl towards shore. In the process of migrating, many nymphs are knocked loose. Also, migration is heaviest near dawn and dusk, so fish a nymph pattern near shore at those times.
Those that make it to shore will climb onto alder trunks, grass stems, exposed rocks, and other out-of-the-water objects. The winged adult then emerges. And what a bug it is! At two-and-a-half inches long, with two pairs of wings and an orange body, it's hard to miss an adult salmonfly.
For as long as three weeks, the adults crawl around on streamside vegetation in search of a mate. Females then fly over the water, plop on the surface, and deposit their eggs. Or get sucked down by big trout. Dry flies are useful when the females return to the water. But dries are also effective throughout the entire hatch period because adults often end up on the water, either because the wind blew them there or just through bad luck.
Water temperature plays a key role in the salmonfly hatch. Hatches often start in the downstream sections of rivers where the water has had more time to warm up. Then the hatch works its way upstream.
After the hatch, there are still nymphs in the river, and trout will switch back to them in earnest in the fall. Some anglers use a smaller fly in the fall, on the theory that the biggest nymphs hatched in spring. It sounds good, but I've never noticed that the trout cared one way or the other.
Articles About Salmonflies
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Motion Flies In fly patterns as in politics, illusion can trump reality. Jeff Morgan
Last-Minute Stones Salmonfly/golden stone season is upon us. How's your fly box? Try putting these three patterns in there! Jeff Morgan
Salmonfly Nymphs Salmonfly nymphs are a the Big Mac of the river, an irrestible morsel for trout. Spring and fall are the best times to cast their imitations. Mike Schoby
Fishing the Salmonfly Hatch Adored by anglers and trout, salmonflies are the big bug of the river. But many anglers don't approach the fish and the "hatch" as they should--and loose fish they shouldn't. Scott Richmond