Officials issue warning after spotting predatory fish in river where it doesn't belong

Officials are urging anglers in Montana's Flathead River to reconsider "catch and release" practices when it comes to invasive brown trout.

What's happening?

As Field & Stream reported, the predatory fish has been detected in the river, according to a notice from the Montana Department of Fish, Wildlife & Parks.

The Flathead is among the few waterways in Montana still free of brown trout. They imperil native trout such as bull trout and westslope cutthroat trout by consuming their young fish and beating them to valuable resources.

"Protecting our native trout populations is a priority," declared FWP Regional Fisheries Manager Mike Hensler, per Field & Stream. "Brown trout pose a threat to native species in the Flathead drainage, and we need the public's help to manage this invasive species."

Another set of factors that gives brown trout the upper hand is the timing of their spawning season and their resilience to environmental challenges, per the Montana Field Guide.

Why is the spread of brown trout important?

Trout populations in Montana are already facing a series of concerning developments that are lowering their numbers. In response, the state has implemented protective measures.

The arrival of an invasive species in what was formerly a safe harbor for native trout threatens these fish even more. It's not just brown trout that are threatening native species in Montana. A plethora of invaders, such as the faucet snail, zebra mussels, and water lilies, have come from across the globe.

Due to their relentlessness and adaptability, the arrival of brown trout could end up spelling doom for native fish less capable of competing with them or contending with environmental challenges.

What's being done about brown trout in the Flathead River?

The FWP plans to verify the presence of brown trout through environmental DNA sampling. That can help illuminate the infiltration in the Flathead River and dictate further steps to combat the spread. The department reiterated that moving live fish from one body of water to another is strictly forbidden.

If an angler encounters a brown trout in the Flathead River or its tributaries, the FWP recommends they immediately kill the fish. Once that's done, they urge reporting it to their FWP regional office with details of the catch, including the time and location. 

That will not only take out an invasive fish but also help the FWP expand its base of knowledge about where the fish is in the river.

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