Montana fly fishing near Big Sky, Montana on the Gallatin River, Madison River, and Yellowstone Rivers
‘Tis the season for the stonefly: Big water and big hatches
Spring to summer in mountain country is defined by change—the snow line creeps up, rivers are full and often dirty, and the fly fishing community is gearing up for summer. In our world, we're on the river more than not. When we're not on the river, we're checking streamflows and weather reports to find stable, or dropping, rivers. With the anxiety of runoff season, a little sweat equity often results in finding some of the best fishing of the year.
If finding fishable water is the challenge, thankfully fly choice and fishing method is often simple. High and dirty rivers mean stoneflies are on the move. Plecoptera, is the Latin order that defines stoneflies, but with over 3,500 species worldwide, none of us room in our fly boxes for all of them. Therefore as anglers we ditch the complex and go with simplicity: stick to the common names of stoneflies and you will be able to talk the talk just fine.
Salmonflies (Pteronarcys ) are the first stoneflies to hatch, followed by Golden Stoneflies (Perlidae), and later in summer Yellow Stones/Sallies (Perlodidae). Despite their differences, all stoneflies hatch in similar ways—by crawling to bankside structure and shedding a nymphal “shuck”or shell and emerging as flying adults. Think of the nymphal shuck as a cocoon for the emerging adult butterfly. We are still several weeks away from the emergences of adult salmonflies, but, if you want to catch fish before the hatches, and the masses of anglers, you need to understand how to fish stonefly nymphs.
Bank on it. Stoneflies need structure to hatch. With very few exceptions, they crawl out of the water onto rocks, sticks, or other shoreline objects. As these nymphs are migrating to shore, hungry trout know this and gobble up as many nymphs as possible. It’s as if the fish gods created this hatch so we could fish during runoff, because the trout’s main source of food is near the bank, it means we can still fish during periods of high water. With rivers that are bankfull, wading into swift current is unsafe. It’s a good thing that nearly all of your fishing should occur while standing near, or even on, the bank and fishing very tight to it.
Shorten and strengthen the system. Because the fish are tight to the banks, decrease the length of your leader and increase the strength of your tippet. When casting, a shorter leader will be easier to turn-over larger, heavier, flies. Plus, if you’re fishing while standing on the bank you want to avoid snagging branches or trees on your backcast or bankside structure on your presentation cast. Since none of us are perfect, the occasional snag occurs. A stouter tippet ensures you keep your flies more often. Increasing the strength of your tippet also helps if you hang-up on the bottom, because the dirty water might make it difficult to see underwater structure. A stronger tippet also comes in handy when you hook that trophy trout and need to land it in fast current.
Weight for it, weight for it. Accept the fact that until we see adult stoneflies, if you want to catch fish are you are going to fish subsurface. Even though the fish are tight to the banks, the current is often heavy and fast. Adding weight to your fly or your leader is essential. My favorite stonefly nymph pattern is a Pat’s Rubberlegs. This fly is very similar to a Girdle Bug or Bitch Creek and imitates a stonefly nymphs. To ensure stonefly nymphs have weight tied into the fly, typically wrapped on the hook shank during the tying process. Adding weight in the form of putty or split shot to the leader may be important as well. We like to start with as little weight as possible then add weight as needed if we're not getting deep enough, fast enough.
Double the pleasure. Simply put, fish two flies at all times. This increases your odds for a strike and adds a little more weight in the rig. The second fly can be tied directly off the bend of the hook of the first fly using a clinch knot.
Strike on anything. Using a strike indicator is very helpful when stoneflies are on the move. An indicator serves two main purposes: it allows you to detect a strike and holds your flies at the right depth. If you see it move in any erratic motion, set the hook. A good rule of how far to place the indicator above the first fly is twice the depth of the water. However, this varies based on current speed, flies on your leader, and your ability to mend effectively. We use indicators we can move easily, such as the AirFlo AirLock.
For most of our local rivers and streams, stoneflies make up the majority of a trout’s diet. Trout eat stoneflies year-round, but as spring fades into summer stonefly nymphs become more active and their emergence into adults, aka hatches and subsequently dry fly fishing, begins. Until the adults flutter about, if you want to catch fish you’ll need to adjust your tactics. If you don’t want to do that, then I’m sure there’s a bowling league somewhere that needs a few more rollers.
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