Gibbon River closure map

Yellowstone National Park fisheries biologists will soon discharge the fish poison rotenone into much of the Upper Gibbon River drainage, which will be off-limits for part of September.

The project, which runs Monday until Sept. 13, is designed to scrub nonnative rainbow trout and brook trout out of the watershed, a step that would enable the reintroduction of westslope cutthroat trout and Arctic grayling.

Those two species are native to the Yellowstone River watershed but are not thought to be native to the Upper Gibbon system. The mottled sculpin, a minnow, is the only fish species known to naturally occur in the Gibbon above Gibbon Falls, park documents say.

Among eight stream watersheds from which Yellowstone has removed or plans to remove exotic species, the Gibbon project is by far the most ambitious. An estimated 111 miles of stream and seeps will be poisoned, according to the park’s native fish conservation plan.

The Upper Gibbon drainage includes Grebe, Wolf and Ice lakes and the streams that flow out from those waters. To make sure the nonnative rainbow and brook trout are wiped out, the treatments may be repeated in 2020. Reintroduction of fish is to begin in 2020 or 2021.

Westslope cutthroat and Arctic grayling were nearly eliminated from Yellowstone due to being out-competed and hybridizing with exotic trout. In recent years, the park has tried to restore both species to the East Fork of Specimen Creek, Goose Lake and Grayling Creek.

Starting Monday, Virginia Cascades Drive, Wolf Lake Trail and Wolf Lake Cutoff trail up to Ice Lake will be off-limits. Backcountry areas north and south of the road between Canyon and Norris junctions are also closed. The closures will lift if the poisoning operations wrap up early.

Contact Mike Koshmrl at 732-7067 or

Mike has reported on the Greater Yellowstone Ecosystem's wildlife, wildlands and the agencies that manage them for 7 years. A native Minnesotan, he arrived in the West to study environmental journalism at the University of Colorado.

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(3) comments

Larry Day

No, they don't "think" they're eliminating non-native fish from this section of the Gibbon, rainbows and brook trout were introduced to the region and there is ample historical record of the introduction and of their absence prior to that. We have both a responsibility and a legal obligation to protect our threatened native fishes. This project is part of that effort and uses well-established best fisheries management practices. This fall I will be enjoying the spectacular fishery down stream of the project and am not concerned about negative impacts. In a few years you will see that there was little to be concerned about. They do know what they're doing.

Marion Dickinson

Sad to think they are killing so many great fish because they "think" they may not be native to that particular creek.

Fish Biologist

Like Larry says, “thinking” a fish is native is not the case. We know the origin of fishes, and the nonnative rainbow trout, brown trout, and brook trou, along with climate change and habitat degradation are pushing the actual, honest-to-God natives to extinction. Don’t be sad. This is cause for celebration, unless you find extinction of beautiful, native fish with ever-decreasing distribution and increasing threats to be good or indifferent. Rainbow trout are native to the west coast of North America, but have been introduced to every continent except Antarctica, and they lead to extinction of native fish worldwide. Brook trout are decimating most of the native trout in the West. Google the Western Native Trout Initiative for information on our diversity and beauty of native trout and learn how threatened they are by known nonnatives.

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