Rotenone treatment scheduled in Virgin River Gorge for nonnative fish removal

Utah's Division of Wildlife Resources Biologists measure Woundfin for release into the Virgin River, Washington County, Utah, March 10, 2011 | Photo DWR Wahweap Hatchery, St. George News

PHOENIX – The Arizona Game and Fish Department, Utah Division of Wildlife Resources and Virgin River Program will conduct a fish management project using rotenone in the Virgin River Gorge in southwest Utah and northwest Arizona to remove invasive red shiner and restore habitat in the Virgin River for native fishes.

Male red shiner in full breeding colors | Photo by Marine discovery via Wikimedia Commons – own work, GFDL; St. George News

The treatment is scheduled to begin the week of June 9, but depending on river flows and weather, may be delayed for an additional week.  During the treatment, access will be restricted to the project area, including the Cedar Pocket campground.

Virgin River Program partners are working on the project to ensure continued water delivery to the cities of St. George, Utah, Mesquite, Nev., Beaver Dam, Ariz., and to the surrounding areas. The implementation of this project will meet recovery goals for the endangered woundfin, one of the rarest species of fish in the southwest. Woundfin are threatened by red shiner, a non-native bait fish that thrives in the project area’s 17-mile stretch of the river between Utah’s State Line Fish Barrier and Arizona’s Virgin River Gorge Fish Barrier. The Arizona Game and Fish Commission reviewed the project’s environmental impact documentation and approved implementation of the project.

During the week of June 9, motorists along Interstate 15 and residents in nearby towns in Arizona and Nevada might notice the Virgin River colored red from a non-toxic, biodegradable dye. Arizona Game and Fish biologists will conduct a temporary dye flow test of the Virgin River to determine the flow rate of the river through the treatment area. The dye might also be used during the treatment week of June 16 to aid rotenone applicators.

Prior to the rotenone treatment, the Arizona Game and Fish Department and partners from the Virgin River Program will salvage native fish from the treatment reach and move them to safe refuge habitats and holding facilities. The remaining fish will be eradicated within the reach, targeting the invasive red shiner, which has moved up from Lake Mead into the upper watershed of the Virgin River.

Rotenone use is regulated by several state and federal laws and is registered for use to remove undesirable fish by the U.S. Environmental Protection Agency. There are no known side effects to humans, birds, or other mammals when rotenone is used according to the product label.

Potassium permanganate, a water purifier, will be used to deactivate the rotenone once the treatment is complete. Water may be temporarily discolored by the permanganate in the Virgin River Gorge.

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