Even the name is impressive. It makes a person think of something from the age of dinosaurs. In fact, stoneflies have been around for quite a while. One genus of stoneflies, Mesoluectra, was around during the Jurassic period, back when dinosaurs reigned supreme in the great steamy marshlands of Montana.
Stoneflies are a member of the insect class of arthropods, and there are some 3,500 known species worldwide, and they’re found in every continent except Antarctica.
According to a Montana State University website, there are nine families of stoneflies present in Montana and 113 species, ranking us 6th among the states and provinces.
Trout, being opportunistic, as well as always on the lookout for their next meal, make stoneflies an important part of their diet. From the skwala, that shows up in springtime, to golden stones, yellow sallies and others, stoneflies in one stage of life or another become fish food. Chances are that a stonefly imitation will catch fish much of the time.
While stoneflies feed trout year around, it’s the Pteronarcys bugs, probably better known as the salmonfly, that grab our attention. They’re big, up to around two inches long, and colorful, with their orange abdomen. They’re widespread, inhabiting rivers of the west from British Columbia to California and on both sides of the Continental Divide. The Big Hole River of southwest Montana is known for its salmonfly hatch and, while the dates aren’t set in stone, this coming week is likely when the hatch will be on.
Stoneflies spend most of their life along the river bottoms. While some stoneflies are carnivorous, Pteronarcys stoneflies are vegetarian, living by chewing up small woody debris. After several years of submarine existence, the insects reach their final phase of life, as they move towards the shoreline of rivers, crawl out onto rocks and onto vegetation, such as grasses or willows. They then emerge from their exoskeleton and become a full-fledged winged insect.
After emerging, they take some time to let their wings dry and then they search out a mate. Nature takes its course and females return to the water where they flutter along the water’s surface, dipping the tip of their abdomen in the water and releasing eggs.
It is during this final part of life that the interests of trout and anglers intersect. When things work right, that fluttering salmonfly attracts fish in search of a big bite of protein. Some of the time, the trout finds itself with a hook in its jaw, having been tricked by a clump of feathers and hair tied onto a fishhook to resemble a stonefly.
Fly-fishing during the salmonfly hatch can be exciting, when a good-sized trout smashes into a dry fly, even when the trout ends up not taking it, or a sizzling run when it does get hooked. When it happens it creates instant memories that keep us warm during the winter.
While the salmonfly hatch can be exciting, it’s not necessarily the best fly-fishing time of the year, especially for the DIY angler. It usually happens when waterflows are high with spring runoff and the wade angler has to exercise a lot of caution when stepping into the water. A misstep can quickly become a misadventure.
If you like solitude on the water, the salmonfly hatch may not be for you. Looking upstream along the river you’re likely to see a long line of drift boats and rubber rafts working the shoreline. Some are guides and clients, and some are local anglers. It’s also the peak period for recreational floaters taking advantage of warm, sunny days to float the river. You can usually spot the recreational floaters. They’re the rubber rafts with 4-8 passengers with perhaps one person actually casting a spinning rod.
While the salmonfly hatch can sometimes be kind of a zoo, just remember that going to the zoo on a warm day in June can be a lot of fun. Actually, it’s one of those don’t miss events. So, go fish, remember the sunscreen and rain jacket, and create some memories.