The Dixie National Forest is poised to wipe out a sport fishery on two streams to restore native trout to parts of the Paunsaugunt Plateau.
In coordination with Utah wildlife officials, the forest is looking to return populations of Bonneville cutthroat trout, along with native minnows and suckers, to the upper East Fork of the Sevier River, which will require killing all the fish, including beloved rainbow and brown trout.
For the first phase of the project, Upper Kanab and Blubber creeks, just west of Bryce Canyon National Park, will be closed for several days next month while biologists apply the fish-killing poison rotenone.
The project is part of a larger effort to restore cutthroat to 36 miles of interconnected streams above Tropic Reservoir, as well as isolated segments downstream, such as Hunt, Birch and Horse creeks.
“One of the challenges to restoring native trout is finding areas where fish will be able to persist following a disturbance without additional management from us because it requires that species to occupy long distances of interconnected stream,” said Dixie fish biologist Mike Golden. “This project provides us with that opportunity.”
Blubber Creek will be closed Sept. 5 to 7 and Upper Kanab will be closed Sept. 11 to 13.
Bonneville cutthroat is a subspecies whose historic range is confined to the streams that once fed the massive Lake Bonneville that covered northwestern Utah 14,000 years ago.
After the introduction of nonnative trout, cutthroats disappeared from stream after stream until there remained only six known populations in 1978, according to the Utah Division of Wildlife Resources (DWR). Since that nadir the number of populations has rebounded to 261.
Richard Hepworth, DWR’s aquatics program manager, said brook and brown trout spawn in the fall, giving those species an advantage over Bonneville cutthroat that spawn in the spring.
Cutthroat restoration projects, including in Salt Lake County’s Mill Creek Canyon, have been pursued all over the West and occasionally get bogged in controversy.
The Uinta-Wasatch-Cache National Forest has initiated an environmental impact study on a similar proposal for the north slope of the Uinta Mountains. This forest intends to begin poisoning stretches of the West Fork Smiths Fork drainage next year and restocking them with Colorado River cutthroat trout and other native fish, such as sculpin, speckled dace and mountain sucker, according to a notice posted Friday on the Federal Register.
DWR might also stock tiger trout, a sterile hybrid, to provide sport fishing opportunities while cutthroat populations are getting established. Forest Service officials are accepting comments on the Uinta project through Sept. 25.
Applying toxins to streams can make people nervous, but biologists take numerous steps to minimize collateral damage to nontarget organisms, such as small invertebrates and amphibians.
Trout Unlimited supports these efforts and sometimes lends a hand.
“In the inland West, cutthroat are the only native trout. We love to see our native fish and we don’t want them pushed out by nonnative sport fish,” said Jordan Nielson, a Utah-based project manager for the conservation group. “We don’t want to see any fish end up on the [the Endangered Species Act] list. The more miles we make sure we have for native trout, the better.“
Nielson emphasized that nonnative sport fish have a place in Western streams, but eliminating them from select streams, he said, is in the best interest of the angling community. The best streams for such projects are in high-elevation headwaters, which is why the Forest Service is often involved. It is also essential that barriers can be installed to keep nonnative fish from migrating back in.
“You’re finding a place with a good cold water stream and good flows, plenty of forage and bugs in the water,” Nielson said. “You need steeper banks and gradients to put in a barrier. It has to be accessible. Rotenone treatments can get expensive if you need a helicopter.”
Rotenone is especially toxic to gill-breathing organisms, but considered benign to humans and wildlife.
In next week’s application on the Sevier creeks, biologists will use drip barrels to distribute a 5 percent rotenone solution for three to eight hours. The goal is to achieve in-stream rotenone concentrations of 80 parts per billion, a level lethal to fish, but safe for most other aquatic life. They will apply an oxidizing agent to the creeks that neutralizes the toxin so it won’t harm fish downstream.
The Dixie also plans to install six permanent and three temporary fish barriers in the East Fork drainage to prevent nonnative fish from migrating upstream. Meanwhile, forest officials are pursuing another multiyear Bonneville restoration project on Mammoth Creek tributaries on the west side of the Sevier drainage.