Portions of East Fork Sevier River in Dixie National Forest to be closed for rotenone treatment

Stock image, St. George News

SOUTHERN UTAH — As part of a range-wide conservation agreement and strategy for the native Bonneville cutthroat trout, the Utah Division of Wildlife Resources will conduct a restoration project using the piscicide rotenone. The project will require a temporary closure within the East Fork Sevier River drainage on the Dixie National Forest beginning Sept. 5.

“We are trying to keep the species off the Endangered Species list, as well as restore native species back to their historic habitat,” Richard Hepworth, aquatics program manager for UDWR, said in a press release.

The rotenone treatment is aimed to rid all species of fish in targeted streams, ponds, lakes and tributaries in order to restore the native Bonneville cutthroat trout – along with other native minnows and suckers – to a portion of the East Fork Sevier River drainage.

A temporary closure of these areas during the piscicide application will be necessary to allow ground crews to safely work in and around the lakes and streams without harm or injury to the public. All use of the water (wading, fishing, swimming, etc.) within the project area will be prohibited during piscicide application and neutralization.

The East Fork Sevier River is one of the primary tributaries of the Sevier River. Since the 1970s, only two remnant populations – meaning they have persisted since the time of settlement – of native Bonneville cutthroat trout have been found in the entire East Fork Sevier River drainage.

The fish is native to Utah but has declined for many reasons, including past introductions of nonnative trout, Hepworth said.

“Brook trout, brown trout and rainbow trout were stocked as sport fish in the past, but are not native to the area,” he said. “Brook and brown trout spawn in the fall giving their young a competitive advantage over spring spawning BCT (Bonneville cutthroat trout) and rainbow trout hybridize with BCT. These factors have resulted in those trout species overtaking BCT throughout most of the Bonneville Basin.”

The Blubber Creek and Upper Kanab Creek restoration projects are part of a larger effort designed to restore over 50 miles of stream for the cutthroat trout and other native fish, including 36 miles of interconnected streams upstream from Tropic Reservoir.

Liquid rotenone (product name: Prenfish) will be applied to target waters using drip barrels. Depending on their location, most drips will run for three to eight hours.

The active ingredient in liquid rotenone is a powder derived from the roots of a South American plant. Rotenone is specifically poisonous to gilled organisms because it interrupts oxygen uptake from the water at the cellular level. After the rotenone has been applied, potassium permanganate, an oxidizing agent, will be applied to the rotenone treated waters below the target area which deactivates the rotenone in those areas.

Although liquid rotenone is relatively benign to humans, fish treated with the chemical have not been cleared by the Food and Drug Administration for human consumption. For that reason, fish that die during the project cannot be salvaged.

After successful removal of non-native trout, Bonneville cutthroat trout will be introduced to the stream. Similar restoration projects involving Utah’s native trout are underway throughout the state.

The following areas will be closed during the treatments for protection of public health and safety:

  • Blubber Creek – Sept. 5-7 – Off forest system roads and within 100 feet of Blubber Creek and its tributaries from the confluence of Blubber Creek with the East Fork Sevier River upstream through all the Blubber Creek drainage headwaters (T37S, R41/2W, Sections 26, 27, 34, 35 and 36; Salt Lake City Baseline and Meridian).
  • Upper Kanab Creek – Sept. 11-13 – Off forest system roads and within 100 feet of Upper Kanab Creek and its tributaries from the confluence of Upper Kanab Creek with the East Fork Sevier River upstream through all the Upper Kanab Creek drainage headwaters (T38S, R41/2W, Sections 1, 2, 3, 10, 16 and 21; Salt Lake City Baseline and Meridian).

For more information on the BCT restoration project, please contact Michael Hadley, Southern Region aquatics biologist, Utah Division of Wildlife Resources at 435-691-2204 or Kacy Ellsworth, Dixie National Forest public affairs officer at 435-865-3700.


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