Yellowstone National Park staff will use a fish toxin next week to further eliminate non-native trout species in the ongoing effort to restore native trout, according to a news release.

From Monday through Aug. 26, park staff will use the fish toxin rotenone to remove non-native rainbow trout and brook trout in the upper Gibbon river drainage.

Rotenone is a naturally occurring chemical compound derived from the roots of tropical plants.

Biologists then will add potassium permanganate to the water to remove the effects of rotenone and prevent impacts to downstream waters. These treatments will be repeated in 2019 and, if needed, 2020.

The upper Gibbon River drainage is in the central portion of Yellowstone National Park and includes streams that flow out of Grebe, Wolf, and Ice lakes. The Wolf Lake Trail and Virginia Cascades Drive will be closed to the public during this project.

Once nonnative fish are removed, biologists will reintroduce native fish species to the streams in this area in 2021.

Bad trout -- Yellowstone invasive species brook trout. Wyoming Game and Fish Department

This work continues the park’s efforts to create refuges that support the reintroduction of native westslope cutthroat trout and fluvial arctic grayling, the park’s native grayling strain.

The historic stocking of non-native fish nearly eliminated these species from Yellowstone.

In recent years the park has restored them to the East Fork of Specimen Creek, Goose Lake, and Grayling Creek. Documents describing this work can be found on the National Park Service planning website.