Salmonflies will soon be fluttering

By Patrick Straub EBS Fishing Columnist

For many of us freestone anglers, the first few weeks of June are challenging because the desire to fish our favorite undammed rivers is squelched due to spring runoff.

However, we are willing to take the good with the bad—without a hefty snowpack and a long runoff, our late summer stream flows can be low, causing warm water conditions. Patience during this time of muddy water and high flows can pay off big, because salmonflies are the next major local hatch.

For those new to fly fishing, trout mostly eat waterborne insects that generally measure under a half-inch in size. The salmonfly can reach lengths of 3.5 inches and when these large insects hatch on our local waters the trout respond by binge eating. Be prepared to enjoy this window of feeding abandon with the following tips.

Know the insect’s habits. Salmonflies hatch from nymphs, which live in the water year round. When conditions warrant, the nymphs begin to migrate toward a river’s shore and bankside structure, where they crawl out of the water, shed a cocoon-like case called a shuck, and become an adult salmonfly.

Once they’re out of the water they find a mate, then the female takes flight and lays her eggs by dragging her tail (ovipositor) in a river. This whole process of nymph migration to mating can take a single day, or up to a week.

Understand weather and stream flow patterns.
Fishing a salmonfly hatch is equal parts study and luck. Salmonflies hatch shortly after a river has reached its peak runoff and is experiencing a consistent drop in flow. Dropping stream flows are crucial, but so is river clarity. They typically go hand-in-hand—as a river drops it usually clears.

Weather conditions dictate when a hatch might occur and how long it will last. Cooler weather means a hatch will be delayed and last longer; warm and sunny days cause a hatch to happen sooner and move faster along a reach of river.

Follow the hatch. Salmonfly hatches often move upstream as conditions warrant. Think of the hatch as two pieces of a puzzle—the nymphs migrate first and then hatch into adults. For example, on a Monday the nymphs could be active in one location, then at another location upstream on Tuesday. But on Wednesday the nymphs that were active on Monday might begin hatching so you may want to return to that location and fish dry flies. Knowing this allows you to fish a hatch for its duration.

Tackle your tackle. Most of your fishing will occur near bankside structure if you’re casting dry flies, or subsurface if you’re fishing nymphs. Losing some flies is inevitable—rivers are high and off color, two factors working against you. Counter this by using stronger tippets: Fish 1X as the norm, 2X if you feel like you’re not getting the drift you need. Fishing 3X and 4X means you will lose more flies. That’s great for your local fly shop’s bottom line, but not ideal if you want to celebrate your catch with a fancy dinner.

Be adventurous. This hatch isn’t scheduled around 8 a.m. to 5 p.m., Monday through Friday workweeks. But that doesn’t mean you can’t fish it—like my toddler, you too can be up at 5 a.m. Get on the water early, fish a few hours and stumble into work; or with our long summer days, fish after work and be on the water until dark.

But be safe. Since these insects hatch when rivers are still swollen with runoff, exercise caution when fishing. The best fishing will be near the bank, so wading deep into a river is rarely necessary. If you float, be sure you know your limitations or float with an experienced boat handler. Getting home safely is the most important part of any fishing trip. If you don’t make it home, you can’t fish again.

Seeking out and fishing a salmonfly hatch requires patience, knowledge and some luck, so having the correct mindset is important. Knowing which came first—the trout eating the salmonfly or the salmonfly hatching after a long runoff—is not that crucial.

In fact, if you actually care about the correct answer to the salmonfly puzzle, then perhaps this hatch isn’t for you. There are plenty of empty chairs at your local chess league during the next few weeks.

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 is co-director of the Montana Fishing Guide School, and co-owns a guide service on the Missouri River.