By Patrick Straub EBS Fishing Columnist

Runoff season is finally over and our local rivers are clear and in prime form. Along with plenty of smiles on the faces of local anglers, the trout in our rivers have been happy as well—big bug season gives them plenty of opportunities for wholesome meals.

For the next few weeks, local anglers need to brush up on their stonefly entomology. Stoneflies, class insecta and order lecoptera, have over 600 species worldwide and range in sizes from 3/8 of an inch to 3 inches. Of the 600 hundred species, your homework is easy as only three are important in our area this time of year. They are the salmon fly (Pteronarcys californica); golden stoneflies (family Perlidae); and Yellow Sally stoneflies (Isoperla fulva or mormona). Don’t worry about the Latin nomenclature, I mainly included those because I found them on Google. 

Here’s some help to get the most out of fishing these exciting hatches. 

Stonefly lifecycle. Stonefly nymphs are in our rivers year-round. Like their adult counterparts, their size varies. As rivers drop and clear after runoff, stonefly nymphs become more active and begin a migration to streamside structure to hatch. Fishing nymphs near and along streamside structure during this migration can be quite rewarding. The nymphs will hatch into adults out of the water and the evidence is left by a vacant exoskeleton. Adult stoneflies work to find a mate by either crawling or flying. Once a mate is found, females will then fly above the water and land, laying eggs as they land. It is during these mating and egg-laying timeframes that adults are readily available to hungry trout. 

Salmon flies. These are the largest of the stoneflies and hatch immediately after runoff. The hatch moves upstream as water temperatures rise. Right now, the best place to find trout eating adult salmon flies will be the upper Gallatin south of Big Sky and the Yellowstone River in and around Yellowstone National Park. Their 2- to 3-inch, orange-colored bodies make them easy to identify. 

Golden stoneflies. Slightly smaller in size than salmon flies, “goldens” hatch a day or two after salmon flies. They can be found on the Lower and Upper Madison rivers, the Gallatin River and the Yellowstone River up to a week after salmon flies have hatched. A variety of golden stone species exist, but only be concerned with matching size and color—leave the Latin names for those anglers you’d leave off the party invite list anyway. Most golden stonefly adults will be around 2 inches long. 

Yellow sally stoneflies. These are the smallest of the stonefly species, yet they hatch in the most abundance and the most frequently. Unlike salmon flies or golden stone flies that sees a hatch move through a stretch of river, Yellow sally stoneflies will hatch for days in the same section. Unlike salmon flies and stoneflies, Yellow sallies hatch more like mayflies and caddis as the nymphs emerge slowly through the water column and the hatched adults fly over the water’s surface in dancing-like flights to mate and lay eggs. Adults range in size from hook sizes 10 to 18 with most being 10 to 14. 

Best fly patterns for each species. For salmon and golden stonefly nymphs a Pat’s Rubberlegs in sizes 8 through 12 is ideal. Color choice is debatable but choose a pattern with contrasting colors such as black and brown or brown and orange. For yellow sally nymphs, a size 14 and 16 Iron Sally is a local favorite and works year-round. For salmon and golden stonefly adults, a Chubby Chernobyl is a proven pattern and allows a larger nymph to be fished as a dropper. Choose the corresponding color and size if you are fishing salmon or golden stoneflies. Other successful salmon and golden stonefly dry flies are Fat Frank, Fluttering and Rouge Foam in sizes 4 through 8. For yellow sallies try Micro-Frank, Para-Sally, and Stimi Chew-Toy.

Stoneflies on our local rivers are the most anticipated hatches of the year. Perhaps that’s because when they hatch runoff is over and it’s back to fishing, or perhaps they are big bugs and trout rising to eat a large dry off the surface is visual and exhilarating. If you’re angler looking to fish our waters, the reason shouldn’t matter. Getting out and enjoying these large insects should. 

Pat Straub is the author of six books, including “The Frugal Fly Fisher,” “Montana On The Fly,” and “Everything You Always Wanted to Know About Fly Fishing.” He and his wife own Gallatin River Guides in Big Sky. He also co-owns Montana Fishing Outfitters and the Montana Fishing Guide School.