Rare native fish found in Utah, then poisoned by mistake
A project launched by the Utah Division of Wildlife Resources to protect a recently discovered population of rare native trout killed almost every fish in the stream instead. The fish, located in Parley's Creek close to Salt Lake City, were believed to be pure Bonneville cutthroat trout, one of only two varieties of trout native to Utah, and candidates for listing under the Endangered Species Act.
Wildlife officials were attempting to rid a creek upstream of introduced rainbow trout by poisoning the water with rotenone. Rainbows and other non-native trout interbreed with Bonneville cutthroats and are the chief reason the native now occupies less than 1 percent of its former range.
Division staffers were unaware that anything had gone wrong until they were informed by a member of a local fishing club. Paul Dremann, conservation chairman of the Stonefly Society, went to the site Nov. 1 to check on the project.
"The whole stretch was strewn with dead fish," says Dremann. "My reaction was dismay and tremendous anger." Dremann then informed Charlie Thompson, a state fisheries biologist in charge of the project.
"I feel pretty bad about it," says Thompson. "They were really pretty fish."
Thompson says cold weather may have caused the rotenone to maintain its toxicity longer than expected. He also says other chemicals used to neutralize the rotenone may have killed the fish.
"I don't know what could have been done differently," Thompson says. Levels of the poison were kept far below recommended doses, and monitoring stations were carefully watched, he adds. "We worked so darn hard to make sure everything went right."
Critics say that is precisely the problem. Even with the best-laid plans, rotenone can be unpredictable. "It's a crap shoot," says Dremann. "This is a glaring example of how you can plan carefully and it can still go wrong."
Rotenone has killed the wrong fish before. A project on Utah's Fremont River in 1991 killed aquatic life along a 35-mile stretch of the river, including sections that flowed through Capitol Reef National Park. In 1990, 18,000 fish were killed in streams leading to Idaho's Salmon River. Perhaps the most infamous case of rotenone gone wrong occurred in 1962 when 430 miles of the Green River were poisoned, including sections in Dinosaur National Monument.
Rotenone kills fish as well as macro invertebrate species such as caddis flies and stoneflies. It can also kill amphibians in early stages of development. Since the Parley's Creek fish kill, Zach Frankel, director of the Utah Rivers Conservation Council, thinks a moratorium on using rotenone makes sense because the poison is unpredictable. Utah officials acknowledge the problems but say it is the most effective tool they have to control non-native fish. "There's no other way," says Thompson, since alternatives such as electroshocking are ineffective, time-consuming and expensive.
Discovery of the Parley's Creek cutthroats last year had astonished state biologists. They believed that most of Utah's native fish were holding out in remote streams, but the creek winds through a golf course and is not far from Interstate 80, just a 10-minute drive from Salt Lake City.
Two days after the discovery of the accident, wildlife officials found one small Bonneville cutthroat still alive in Parley's Creek. They hope it indicates more fish may have survived.
The writer works out of Salt Lake City, Utah.