Wyoming Game and Fish using chemical to kill nonnative fish in Big Sandy River and Reservoir - Casper, WY Oil City News
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Wyoming Game and Fish using chemical to kill nonnative fish in Big Sandy River and Reservoir

Burbot, a nonnative fish species. (Lucy Wold, Wyoming Game and Fish Department)

CASPER, Wyo. — The Wyoming Game and Fish Department said Thursday it will be taking steps over the next two weeks to eliminate nonnative species from Big Sandy River and Reservoir in an effort to conserve and restore native flannelmouth and bluehead suckers.

The department has spent two and a half month salvaging as many native suckers from a 56-mile stretch of the Big Sandy Reservoir in preparation to treat the water with chemicals to kill the nonnative species.

The river and reservoir will be treated with a chemical called rotenone that is lethal to fish. Game and Fish says the chemical is naturally occurring and found in seeds and stems of some plant species.

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While the chemical kills fish and other “gilled life” at low concentrations, the department says the chemical is not a risk to wildlife, livestock, pets or people.

“It has been used by government agencies to kill fish in rivers and lakes in the United States since 1952,” Game and Fish says.

The Big Sandy River is primary habitat for native flannelmouth and bluehead suckers. Once the nonnative white suckers, longnose suckers and burbot are killed, the native species will be reintroduced into the river and reservoir.

The nonnative suckers are a concern because they can hybridize with the native species or consume native fish.

“The reservoir is being treated to eliminate a large source of nonnative fish, especially the illegally introduced burbot,” Game and Fish said. “White suckers and burbot are significantly reducing the fisheries potential in the reservoir: white suckers bind up the majority of resources in the reservoir and burbot consume trout. The sport fishery in the reservoir will benefit from their removal.”  

Game and Fish says that its efforts to conserve and restore flannelmouth and bluehead suckers has been ongoing since the early 2000s.

Game and Fish said that Green River Region Fisheries Biologist John Walrath can understand why some people question the use of time and money spent on conserving native nongame suckers and chubs, but says that the efforts are done in response to calls for federal protection of wildlife species.

“Populations of flannelmouth and bluehead suckers have declined in Arizona, Colorado, Nevada, New Mexico, Utah and Wyoming,” Walrath said. “The six states have developed a range-wide conservation agreement and strategy with the goal of ensuring the persistence of bluehead sucker and flannelmouth sucker populations throughout their ranges. We believe that, as fisheries managers, we must stay proactive in the management of these two species to keep them from being petitioned for listing under the Federal Endangered Species Act. We do not want these native fish to become endangered, let alone go extinct.”