Every spring across the trout-laden rivers of the American West, something spectacular happens. As runoff begins to subside and the days stretch longer, an enormous insect emerges from the cobbled riverbeds. The Salmonfly—Pteronarcys californica, a massive, prehistoric-looking stonefly that ignites the water with life and draws trout to the surface with a reckless hunger.
The Salmonfly is a species of giant stonefly in the order Plecoptera. They grow up to 3 inches long, being one of the largest aquatic insects in North America. Adults are typically dark brown to black with vivid orange or rust-colored markings on the underside.
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| Pteronarcys californica |
These insects are indicators of pristine river systems, and they require cold, clean, well-oxygenated water to survive. You can find them in rivers like the Colorado, Henry's Fork, Deschutes, Madison, and the Gunnison to name a few.
The Salmonfly’s has a long-life cycle. The nymph stage can last up to 3 to 4 years, the nymph lives beneath the surface, crawling among stones and river bottom debris. They feed on organic matter and slowly mature. As water temperatures climb in late spring, nymphs begin migrating toward the riverbanks in preparation for emergence. During this time, trout will feast on these vulnerable nymphs. At night or early morning, nymphs will crawl out of the water onto rocks, logs, or grasses and split their exoskeletons to become winged adults.
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| The Salmonfly are massive in size. |
Adult Salmonflies have a short terrestrial life of just a week or two. They fly awkwardly, mate, and females return to the river to drop eggs, slapping the water surface and are often easy targets for trout.
For fly fishermen, the Salmonfly hatch is of legend. It is an incredible time of the most explosive dry fly fishing of the year. Witnessing a big trout suddenly rise with abandon and crashing through the water surface to devour these Salmonflies is extraordinary! Timing is everything. The hatch typically runs from mid-May to early July, depending on location, altitude, and weather. Rivers warm from the bottom up, so anglers often follow the hatch upstream over days or weeks.
Dead drifts close to banks, under overhangs, or near logs often draw violent takes from trout lurking for an easy, high-protein snack. If you haven’t experienced this unbelievable kind of dry fly fishing, put it on your fishing agenda to seek and fish it! See you on the river!
