Swinging Flies for Bull Trout

The Flathead River system, including the Bob Marshall Wilderness, is one of the few places where you can legally target bull trout in the U.S. You must purchase a catch card from the state and you can get busy chasing these monsters. It’s no secret that big streamers are the ticket for bull trout but you must have a strong strategy for approach and presentation.

Fishing blind with a streamer will get the job done in the early season but the fish tend to migrate less as flows drop and temperatures increase. Shifting your focus to specific water types and swinging techniques will increase your success rates.

Best Water Types

Focus on the deep pools for bull trout. You can fish the deep water almost exclusively during the hot summer months. Bulls love sitting low and will often hug canyon walls. They will also sit below the heavy drops where the pool begins. The turbulence creates a cold, oxygen rich environment for them. The ideal scenario involves fishing for cutthroats through the pocket water and long runs, and then stopping to swing the big water for bull trout.

You will also see cutthroats feeding in many of the pools. The bull trout will sit down deep immediately below them. They often coexist in this fashion. Pick off a few cutthroats on your dry fly then switch rods for the bull trout.


Work together to locate and target the bull trout. Wherever possible, have one person climb high and gain a vantage point. Use that elevated location to spot fish. Once spotted, direct the angler on where to stand and cast. Watch the fly and note the depth. Make depth adjustments until the fly is close to the fish.

Making the Swing

Position yourself well upstream of the fish. You will need your entire shooting head/sink tip and a good amount of running line to get the fly down. Cast across the river and make a big upstream mend so all the line is above the fly. Leave some slack and pause for a few seconds while the line sinks. When the line goes tight, point the rod tip down river and maintain contact while the fly swings through the water column.

Make adjustments based on your partner’s recommendations. This may involve taking a few steps up river and letting the line sink longer to gain more depth. Placing the fly within a few feet of the fish will increase your chances of getting a reaction.

At Lazy J Bar O Outfitters, we offer summertime expeditions into the Bob Marshall Wilderness to pursue the incredible fly fishing opportunities, including swinging for bull trout. For more information, see our Fly Fishing page.  Give us a call at 406-932-5687 or send us a message for details.