Salomone: Throwing stones in the river.

Fly fishers have a lot of learning to do when it comes to all of the insects that tempt a trout. Of the four main insect groups — midges, caddis flies, mayflies and stoneflies — it is the stoneflies that grow to tremendous proportions. When anglers regularly speak of insects in the size 18 realm, things can get a little crazy when a stonefly nymph on a size 2 hook is knotted to the end of your line. Challenging conditions, seasonal timing and substantial reward make stonefly nymphs a critical component to any fly anglers arsenal.

Spring leads anglers to newly-opened water as the river breaks free from the clutch ice created. Even slightly melted snow and ice increases the volume of a thin, winter river. As the water level rises, the flow does, too. The increased flow wears on the underside of the ice shelf. This results in more water in the river disconnecting insects.

Insects in the nymph stage battle the frigid conditions but inevitably get knocked loose. Stoneflies tumbling in the current create a too-good to pass up scenario. Skinny, undernourished trout are driven to feed the pains of hunger and a large stonefly nymph is just that type of food source.

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Even in the heart of winter, small, black stoneflies surprisingly emerge. Observant anglers will notice the dark insects crawling on white riverbank snow. These are little for stoneflies — like a size 12-16. The small stoneflies are thin in shape, too. They do not have the bulk that other stoneflies possess.

A size 14 black Copper John nymph mimics the thin body shape and still holds significant weight to get the fly down deep. Between the bead head and wire wraps, a black Copper John sinks quickly and rides along the river bottom like a naturally dislodged insect. As the first stoneflies of the year, this is a good transition time to use stonefly nymphs before the high water arrives.

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Trout ride along the river bottom and feed opportunistically. While getting a trout to move even an inch in the cold of winter water is never a possibility, spring begins to give trout more attitude and reason to move. A bulky bite of food curled up and tumbling along in the current is easy pickings for swift swimming trout. Give the fish a fly that represents too much of a temptation and they will move but not chase.

Stoneflies are the largest insects fly fishers regularly present. Examples of stoneflies measured above 3 inches emerge every June during the annual salmonfly hatch. Big and beefy is the best way to describe the salmonfly nymphs. As the nymphs move to stage closer to the bank in preparation for their emergence, increasing flows jar them loose. Rocks move and bugs get flushed into the river with no means for locomotion. Even in off-colored water, dark stoneflies stick out. The well known Bitch Creek nymph works in the few weeks before the hatch and during the emergence.

Pat’s rubber legs — in black, brown or purple — are a “necessity fly” for any true nymphing angler. The big bug creates a noticeable silhouette in stained or murky water. The long, flexible legs deliver an illusion of life from subtle movement. The slight leg motion sells the bug and seals the deal.

Kaufmann’s stonefly nymph has been a consistent producer for years. The wrapped segmented body and realistic wing pad on the back of the bug makes the Kaufmann’s nymph a solid choice for pre-runoff water. A realistic nymph gives fly fishers the best choice before the muddy color inundates the river.

Golden stoneflies are prevalent in the Eagle and Colorado Rivers. They represent a substantial bite but remain smaller than the giant salmonfly nymphs. Umpqua is a leader in the fly-fishing industry and has some of the best fly tier patterns. Mercer’s Biot Epoxy stone is one of the Umpqua patterns fly fishers put a lot of faith in — and for good reason. Mercer’s golden stonefly nymph rides deep, attracts attention and works well in conjunction with another nymph.

The time is now to pick out a small black stonefly nymph and to look ahead for the coming stoneflies. Large Pat’s rubberlegs nymphs will be the anchor temptation for months to come. Stoneflies are big, bad and a mouthful of goodness. Go ahead and throw some stones in the river.

Michael Salomone has lived in the Eagle River valley since 1992. He started his professional guiding career in 2002 and currently guides for Vail Valley Anglers. He lives on the bank of the Eagle River with his wife, Lori, youngest daughter, Ella and a yellow Labrador named Poppy. His published writing has appeared in Southwest Fly Fishing, Fly Rod & Reel, Eastern Fly Fishing, On the Fly, FlyLords, the Pointing Dog Journal, Upland Almanac, TROUT, American Fly Fishing, USA Today Hunt & Fish and Fly Fisherman magazines.