SEVIER, Sevier County — It wasn't long ago that the Clear Creek drainage area north of the Tushar Mountains in Sevier County was a haven for native fish such as Bonneville cutthroat trout.
Michael Hadley, an aquatics biologist with the Utah Division of Wildlife Resources, said it became the largest stream in the state to feature only native fish after biologists completed a four-year rehabilitation project in 2014. But between habitat loss, breeding with and competition from nonnative trout — including rainbow trout and rainbow-cutthroat trout hybrids — those native fish species are once again struggling.
That's why the division is again planning to conduct rotenone treatments in parts of Clear Creek and Fish Creek in an effort to help restore the region's native fish population. The area is set to be at least the third Utah location that will receive rotenone treatment this year. The substance, which comes from the roots of a tropical plant, is toxic to fish but considered harmless for people, pets or other wildlife when used properly.
The area will be closed off from Sept. 20 through Sept. 23 as a result of the plan. At the start of next week, biologists will release the substance at Fish Creek from its confluence with Clear Creek upstream 6 miles, as well as at Clear Creek from its confluence with Fish Creek downstream to the Narrows, which is about 2 miles, according to the division.
State wildlife officials said that biologists will try and capture native fish and relocate them elsewhere before the treatment begins. The substance will otherwise kill off most of the fish remaining in the area, which Hadley said are becoming more and more nonnative species at this point.
"These fish need to be removed in order to preserve the long-term genetic integrity of the native Bonneville cutthroat trout in this area," he said in a statement Monday. "Without the removal of nonnative fish species, we can and have lost entire populations of native cutthroat trout in areas."
State wildlife biologists will then restock the area with native Bonneville cutthroat trout later this year. They also expect other native species in the stream areas not treated this month will travel to help repopulate the treated areas.
The division already conducted a similar treatment plan last month to protect the native Colorado River cutthroat trout in areas of the High Uintas. The agency also plans to do use rotenone at Navajo Lake next month to help trout thrive there.