By Jessianne Wright
EBS Contributor

BIG SKY – During the last half of August, Yellowstone National Park staff moved forward with a native fish reintroduction project within the Upper Gibbon River drainage, which includes streams that flow out of Grebe, Wolf and Ice lakes into the Gibbon River.

Between Aug. 20 and 26, biologists removed nonnative rainbow trout and brook trout from the drainage by applying the piscicide rotenone, which is a fish toxin derived from the roots of tropical plants. Downstream of the treatment area, biologists added potassium permanganate to the water to limit the effects of the rotenone outside of the targeted waters.

Lori Iverson, a spokeswoman for the park, said staff are monitoring the streams to determine the effectiveness of the chemical treatment, though park biologists were unavailable to comment at EBS press time on Aug. 29.

During an April angling information meeting in Bozeman, fisheries biologist Jeff Arnold discussed the Upper Gibbon River drainage project, saying that managers treated the project area with rotenone in 2017 as well. The Lower Gibbon River Falls is a naturally occurring 20-foot cascade waterfall that serves as a barrier to upstream movement of fish into the treatment areas.

In October 2017, 2- to 3-inch-long cutthroat were introduced into Wolf and Grebe lakes to mitigate the impacts of the 2017 fish removal on loons and swans living in the area, Arnold said.

This year’s chemical treatment will be followed by reapplication in 2019 and, if needed, in 2020, to ensure the removal of nonnative fish. Once these nonnative fish are removed, reintroduction of native fish will begin. According to a statement released by park officials, reintroduction is slated for 2021.

The work on the Upper Gibbon is part of a larger reintroduction program aimed at restoring native Yellowstone and westslope cutthroat trout, as well as fluvial arctic grayling, to the park’s waters. Historic stocking of nonnative species has increased competition and predation for many native species, leading to a decline in their populations.

In recent years, park biologists have worked to restore native populations in the East Fork of Specimen Creek, Goose Lake and Grayling Creek.

Visit nps.gov/yell to learn more about the Native Fish Conservation Plan.