CEDAR CITY, Utah (ABC4) – Fish in two more Utah waterbodies are slated to be poisoned in late September as wildlife officials work to combat some trout hybrids threatening the native species. A similar treatment plan is scheduled for October for a Kane County lake.

Parts of Clear Creek and Fish Creek in Iron County will be treated with rotenone on Sept. 20-21, according to the Utah Division of Wildlife Resources. The treatment is in an effort to help restore native Bonneville cutthroat trout in these areas, which are part of the trout’s native range.

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Treatments at Fish Creek will be from its confluence with Clear Creek upstream six miles and at Clear Creek from its confluence with Fish Creek downstream for two miles to the Narrows.

What is rotenone

According to DWR officials, rotenone is a natural substance from the roots of a tropical plant in the bean family. Biologists will use an extremely low quantity of the substance to treat the streams. While it is not dangerous to people, pets, or other wildlife, rotenone is a respiratory toxin to fish.

As a precaution, DWR asks that you stay out of the area and do not enter the treated water from Sept. 20-23. Signs will be in the area during stream treatments.

Why are rotenone treatments being done?

Just like those planned for Navajo Lake in October, the rotenone treatments are intended to help native fish species in Utah and restore them to their native ranges. Habitat loss, breeding with non-native trout, and competition from non-native trout have caused dramatic declines in native cutthroat trout populations around the West, causing concerns about the species’ future.

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“Native fish species, including Bonneville cutthroat trout, were restored to the Clear Creek drainage between 2010 and 2014,” DWR Aquatics Biologist Michael Hadley says. “At the completion of that project, the Clear Creek drainage was the largest stream system in Utah populated by only native fish species. However, in recent years, rainbow trout and rainbow/ cutthroat trout hybrids have been observed in these creeks. These fish need to be removed in order to preserve the long-term genetic integrity of the native Bonneville cutthroat trout in this area. Without the removal of non-native fish species, we can and have lost entire populations of native cutthroat trout in areas.”

DWR says biologists will work to remove and relocate as many of the native fish as they can before treatments take place.

What happens after the rotenone treatments?

Following the treatments, DWR will restock the creeks with Bonneville cutthroat trout later in the fall. There are populations of native fish upstream and downstream of the treatment area that will help repopulate the streams after the treatment.

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Some fish will also be relocated from other streams to help bolster the native fish population in the area.