Yellowstone National Park staff were killing fish to make room for natives.
The park is continuing a project to eliminate nonnative fish from the upper Gibbon River drainage and eventually reintroduce native fish to streams in that area. The project is part of an overall strategy against nonnative trout species that were introduced into the region decades ago.
Park biologists used rotenone — a fish toxin — to kill nonnative rainbow and brook trout in the streams. Below the treatment area, biologists added potassium permanganate to the water to remove the effects of rotenone so it doesn’t impact downstream waters, according a park news release.
“Rotenone is a naturally occurring chemical compound derived from the roots of tropical plants,” the news release said.
The upper Gibbon River drainage includes streams that flow out of Grebe, Wolf and Ice lakes in the central part of the park. The Wolf Lake Trail and Virginia Cascades Drive that access this area were closed to the public during the project.
“Sometimes falls are used as natural barriers that assist with the project, other times the park will have to create an artificial barrier to help protect the headwaters above the project (from nonnative fish),” Bethany Gassman, public information officers for the park, said in an email Friday.
“To ensure the removal of nonnative fish, these treatments will be repeated in 2019 and if needed, 2020,” the release said. “Reintroduction of native fish will begin in 2021.”
This season’s portion of the project is set to end today.
The park hopes to create “refuges” to support populations of native westslope cutthroat trout and fluvial arctic grayling. The grayling are specific to Yellowstone.
“The historic stocking of nonnative fish nearly eliminated these species from Yellowstone,” the news release said.
In recent years, park projects have restored cutthroat and grayling to the East Fork of Specimen Creek, Goose Lake and Grayling Creek.
