Public Review Begins for Westslope Cutthroat and Bull Trout Preservation Project in Gunsight Lake
By Moosetrack Megan

Posted: May 15, 2023

WEST GLACIER, Mont. [May 15, 2023] – Glacier National Park is seeking public comment by June 14, 2023 on an environmental assessment proposing westslope cutthroat and bull trout preservation in Gunsight Lake. The EA is available for public review and comment for 30 days on the National Park Service (NPS) Planning, Environment & Public Comment (PEPC) website at

Glacier National Park is proposing to remove non-native rainbow trout from Gunsight Lake and establish the lake as secure habitat for native westslope cutthroat trout and bull trout. Action is needed to remove the risk of hybridization to downstream native westslope cutthroat trout, provide westslope cutthroat and bull trout with habitat that is secure from the threats of hybridization and climate change, and support native trout genetics throughout the St. Mary River drainage.

Under the proposal, non-native rainbow trout would be removed from Gunsight Lake using an EPA registered and approved fish toxicant, rotenone. While rotenone degrades naturally with sunlight and water movement, detoxification would be hastened with a neutralizing agent. The neutralizing agent, potassium permanganate, is widely used for the treatment of municipal drinking water and wastewater. Both rotenone and potassium permanganate would dissipate with no detectable long-term changes to water quality.

Project activities would begin early September of 2023 with application in late summer or early fall to reduce the likelihood of non-target organisms being present. Native fish, including westslope cutthroat trout and bull trout, are not currently present in Gunsight Lake. The treatment area and Gunsight Pass Trail would be temporarily closed to the public during rotenone application. The Gunsight Lake wilderness campground would be closed to camping September 1, 2023, until spring of 2024.

Following the removal of the non-native rainbow trout, genetically pure westslope cutthroat trout and bull trout would be translocated into Gunsight Lake, likely by helicopter.

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

The EA evaluates impacts to westslope cutthroat trout; bull trout; amphibians; aquatic macroinvertebrates; zooplankton; grizzly bears; common loons and other water birds; water quality; recommended wilderness; natural soundscapes; and visitor use and experience.

Comments can be posted on the NPS PEPC website at or sent by mail to Superintendent, Glacier National Park, Attn: Gunsight Lake EA, P.O. Box 128, West Glacier, Montana, 59936.

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