Glacier National Park May Begin Removing Non-Native Rainbow Trout

by Amy Myers
Photo by Dennis Anderson/Star Tribune via Getty Images

Last week, Glacier National Park began public scoping for a proposed plan to preserve native fish species in its waterways. In order to do so, the park is conducting an environmental assessment (EA). This will help determine if it needs to remove the non-native rainbow trout from the area.

The plan hopes to help secure the cutthroat and bull trout populations. As it stands, bull trout are a threatened species, according to the Endangered Species Act (ESA). The St. Mary River drainage is the only one in the U.S. where you can find these fish, east of the Continental Divide.

Meanwhile, westslope cutthroat trout may not be in as dire of a state as bull trout. However, the Montana Field Guide states that these fish are “at risk due to very limited and/or potentially declining population numbers, range and/or habitat.” This makes the species vulnerable to extirpation, meaning they’ll no longer exist in the wild in Montana.

Initially, Glacier National Park reported, “Gunsight Lake was historically fishless but stocked in 1916 and 1920-1936 with non-native fish, including rainbow trout, which can migrate downstream and hybridize with native westslope cutthroat trout. The lake is well positioned to provide secure habitat for native fish due to downstream waterfalls that block upstream non-native fish migration.”

Glacier National Park Successfully Removed Another Non-Native Fish Species From Waterways

The park proposes to remove rainbow trout from Gunsight Lake using a fish toxicant. Once the population dies off, officials will then replace them with bull trout and “genetically pure” westslope cutthroat trout.

This isn’t the first time that Glacier National Park has utilized extermination methods. Just three years ago, the park also sought to remove Yellowstone cutthroat trout from a couple of its lakes. Surprisingly, this effort also protected the westslope cutthroat and bull trout.

“In 2019, Glacier National Park in partnership with Montana Fish, Wildlife and Parks, the US Fish and Wildlife Service, and the Glacier National Park Conservancy undertook a similar project in the Camas Creek drainage, successfully removing non-native Yellowstone cutthroat trout from Camas and Evangeline Lakes and translocating native westslope cutthroat trout and bull trout to both lakes,” the park explained.

Even with this success, though, the park stressed that the plan is only in its beginning stages.

“The proposed action is only an initial proposal; no decision to implement any action can be made until the NEPA process, including consideration of reasonable alternatives to the proposed action, is complete,” the park said.

During this stage, the park is conducting public scoping to “identify issues, concerns, and other alternatives” to the plan. Once the environmental assessment is complete, the forum will be open to public comment once more.

To add your insight, head here.