Chasing the Big Bug: The Salmonfly Hatch

It’s that time of year again. The beautiful time in Montana, with snowcapped peaks, full rivers, and hungry trout. Even better, it’s the time of year when prehistoric bugs hatch out of the snowmelt-fed waters, crawl their alienesque bodies onto river rock, and flutter up into bushes to begin the ritual that will bring them back the next year. It’s time for salmonflies.

The annual salmonfly hatch is the most sought after hatch on our local waters. It’s also notoriously difficult to predict and get right. But when you do, the rewards are plentiful.


For a few years, I worked in a local fly shop. Daily, you’d dispense the usual advice on techniques, river conditions, and hatches. But when the big bug was about to pop, it became something altogether different. The shop got busy. The phone rang a lot more. Celebrities with vacation homes would call and name drop to try and get an edge (it didn’t work). Everyone had the same questions: When would it happen? What river would happen first? What bridge were they at?

Suffice it to say, nearly everyone is chasing this event. The lucky (or well-informed) get it right. What does that mean? It means being on a river where you can toss dry flies the size of your pinky all day to trout that simply can’t resist them. It means for once, after a long winter and stubborn spring of nymphing, you win.


Get in on the glut

To say that the trout gorge themselves is an understatement. The bellies of those you catch are distended with salmonflies, individual exoskeletons discernible to the touch through their stretched skin. As the hatch progresses, your takes will become subtler—often devolving to gentle nose-bumps—as the fish literally can’t fit more in their mouths, or say no. When you do set metal to lip, the fish will often have bugs pouring out of their mouths. It’s a beautiful celebration of excess that would meet Gordon Gekko’s standard of approval. Moderation is not a concept aligned with the ethos of the big bug.


How you find ‘em

Depending on the river, yearly snowpack, and spring temps, the hatch can happen anywhere from late May until mid-July. If you want to fish it, it’s a good idea to call a shop or local guide and discuss the best time. Even locals have a hard time predicting the exact location and timing of bugs.

Theories vary on whether you want to be in front of, in the middle of, or just behind the hatch, but if you’re booking a trip, your guide should have ‘em dialed in. The bulk of the hatch will move miles upriver each day and leave the anglers chasing and guessing. Because of this, you want someone who is out on the river every day to help you find the right spot. If you’ve got a river in mind, they’ll have a timeframe for you. If you’ve got a specific date, they’ll have a river.

Salmonflies emerge when the weather is warm, the landscape is green, and the mountains are at their most picturesque. It’s a damn fine time to float down a river. And unless your mouse game is off the hook, it gives you the best opportunity of the year to hit numerous trout on the biggest dry fly in your box.

A friend who guides routinely gets clients into dozens of fish a day when the hatch is at its fullest. Where? Ah, not on the internet my friend. We’ve all got to earn it a little bit.

Photos provided by Luke Koerten, a great guide out of Bozeman, MT