Invasive Brown Trout in the Flathead Drainage Put Native Trout and a World-Class Fishery on Alert

Montana Fish, Wildlife & Parks has confirmed non-native brown trout in the Flathead Drainage, including Ashley Lake and a reported fish from Church Slough. That may not sound like much if you are used to brown trout being treated like a prized sport fish, but in northwest Montana this is a serious red flag.

The Flathead system still holds native westslope cutthroat trout and threatened bull trout. Brown trout do not belong in that drainage. If they get established, they can compete with and prey on other fish, and once a reproducing population spreads through connected water, the problem gets a whole lot harder and more expensive to fight.

FWP fisheries biologist Kenny Breidinger said the agency is taking any brown trout detection in the Flathead seriously because Ashley Lake and Church Slough could become sources for wider spread. That is the right mindset. Invasive species work is not glamorous, but waiting until a fishery is already overrun is how managers end up with fewer tools and worse choices.

Anglers are being asked to help by reporting any brown trout they catch in the drainage. That is practical conservation. The people on the water are often the first early-warning system, and a clear photo, location, and report can matter more than another argument from the bank.

There is nothing anti-fishing about protecting a fishery from the wrong fish in the wrong place. Good management means knowing when harvest, removal, reporting, and quick agency response are all part of keeping wild trout water wild. The Flathead is worth that kind of attention before the damage is permanent.