Yellowstone National Park biologists have announced plans to release toxins into a river to remove exotic fish.
The poisons are expected to be discharged Monday into the upper Gibbon River drainage in northwest Wyoming.
Park officials say the project targets rainbow trout and brook trout native to the Yellowstone River watershed, but not to the upper Gibbon ecosystem.
The following areas are expected to remain closed until Sept. 13:
Virginia Cascades Drive Wolf Lake Trail Wolf Lake Cutoff trail (to Ice Lake) Areas of the backcountry to the north and south between Canyon and Norris Junctions
All campsites in the area will remain open. Closures may lift if the project is completed ahead of schedule.
Park officials say about 110 miles of stream and seeps could be poisoned, and the treatment could be repeated in 2020 to ensure the fish are wiped out.
Officials say this step would enable the reintroduction of westslope cutthroat trout and Arctic grayling planned for 2020 or 2021.