GLEN CANYON NATIONAL RECREATION AREA — The National Park Service and Arizona Game and Fish Department will administer two treatments of the fish toxin rotenone to eliminate invasive green sunfish from a backwater slough.

The slough is located on the Colorado River within Glen Canyon National Recreation Area, 3 miles below the Glen Canyon Dam.

The first treatment is planned between Nov. 2 and Nov. 6, followed by a second treatment 10 days later to address fish that may have hatched after the first treatment.

The treatments will be applied by Arizona Game and Fish Department biologists, pending approval by the Arizona Game and Fish Commission. The cobble bar area surrounding the slough, the slough itself, and a short distance up and downstream will remain closed to the public for the duration of both treatments. The closure is marked by buoys and signs.

Rotenone is a natural substance derived from plant roots. It has been effective at eliminating localized populations of green sunfish, including in the Colorado River Basin.

Since 1990, the Arizona Game and Fish Department has used rotenone as a fish removal tool in 22 waters to support conservation of native fish, control invasive species, and to improve angler opportunities.

The environmental consequences of rotenone are minor, except to fish and invertebrates. Between eight and 30 gallons of rotenone will be applied to treat the slough. Fish will be removed from the area following treatments.

An impermeable fabric barrier will be installed at the mouth of the slough for the duration of the two treatments to minimize exchange of water with the river. Potassium permanganate, a chemical used to purify drinking water, will be added to the slough, and into the river just below the fabric barrier to neutralize the rotenone.