Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana

Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Stream photos

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Sweltsa (Sallfly) Stonefly Nymph Sweltsa (Sallfly) Stonefly Nymph

Dorsal view of a Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington

This species was fairly abundant in a February sample of the upper Yakima.

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27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Arthropod Order Amphipoda (Scuds)

A freshwater amphipod (scud). Tiny crustacean common to many freshwater environments

Dorsal view of a Amphipoda (Scud) Arthropod Adult from Salmon Creek in New York

Scuds can be an extremely important trout food source. They are often the most abundant aquatic macroinvertebrate in their habitat.

They are crustaceans so they don't go through the same life-cycle complications as aquatic insects. They start out as small scuds, grow to be big scuds, and die. The most significant family to anglers is Gammaridae with the species of the Gammarus genus heading up the list. The smaller Hyalella species of the Talitridae can also be important.

Though they all share the same silhouette, they can come in a surprising variety of sizes and colors. They run from size 8 to as small as you wish to imitate. The most common colors are olive or tan, though they can be found with yellow or gray base colors as well. Shading is often illusive to describe with highlights of pink, orange, green and even blue at times. It pays for anglers to notice both size and color differences in the waters they fish.

Where & when

Preferred waters: Best in alkaline water

Scuds are present year-round. They do very well in both lakes and streams. This is especially so in the West with its greater abundance of the alkaline stillwaters preferred by these critters. They're generally associated with slow water and do seem to be the most common there, especially in spring creeks and lakes or ponds with extensive weedy littoral zones (shallows). But some swift-flowing streams still hold good scud populations, and they can even be found in the riffles.

Scuds are very sensitive to light and prefer to remain deeply hidden during the day. Overcast days and periods of low light are the best times for anglers to use their imitations.

Amphipoda Fly Fishing Tips

Highly imitative flies have proven very successful and many anglers swear by them. Gravid female designs with their flashy segments of bright orange may give them that extra "edge" of attraction at times. Most anglers prefer special scud hooks with exaggerated short and rounded shanks, especially for dead drifting. Traditional hooks still have their place for use with active retrieves.

Some respected angling authorities however suggest that fuzzy Hares Ears, Birds Nests, and Zug Bugs are equally effective. They consider specialized scud patterns an unnecessary extravagance taking up precious space in their fly boxes. This is a valid consideration, especially for those anglers that don't regularly fish water where these crustaceans are important. Regardless of fly selection, fishing them in and around weed beds with known populations is often a good choice in low light conditions.