Salmonfly

Scientific Name: Pteronarcys californica

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.

 

How to Match a Salmonfly

Hatches are matched from Westfly's database of "standard" fly patterns.

Nymph
Size 6-10 Kaufmanns Stonefly, Rubber Legs. Dark brown and orange
Bankwater near foilage: indicator, tight line
Adult
Bankwater near foilage: standard dry fly, skating
Adult
Size 6-10 Clarks Stonefly. Darker brown, dark orange
Riffles, moderate-fast runs, backeddies, seams: standard dry fly
Egg-layer
Size 6-10 Stimulator, Madam X. Darker brown, dark orange
Riffles, moderate-fast runs, backeddies, seams: standard dry fly, skating
Egg-layer
Size 6-10 Clarks Stonefly, Chubby Chernobyl, Norm Woods Special, Chubby Norman. Darker brown, dark orange
Riffles, moderate-fast runs, backeddies, seams: standard dry fly

 

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Characteristics

NYMPH COLOR: Black or chocolate brown

ADULT SIZE: 30-50 mm

ADULT COLOR: Dark brown wing, head, and top of abdomen; orange brown bottom of abdomen; orange band just behind head.

OTHER CHARACTERISTICS: Nymph--gills between legs ("hairy armpits"). Female adults can develop dark brown egg sac at rear of abdomen prior to laying eggs.

 

More About Salmonflies