Biologists are hoping that constructing a fish barrier and removing fish from 11.2 miles of the West Fork of the Duchesne River will stop or at least slow down the spread of whirling disease.

Biologists built the barrier and removed the fish after whirling disease was discovered in the main stem of the Duchesne River. The river is in northeastern Utah.

"We don't know if we can completely stop the spread of whirling disease," said Roger Schneidervin, regional aquatics manager for the Utah Division of Wildlife Resources, "but we would sure like to slow it down for a very long time."

To try and slow its spread, DWR biologists have constructed a small barrier above the Vat Diversion. The barrier will stop fish from moving upstream.

"We then treated the stream between the new barrier and the Vat Diversion with rotenone to remove all of the fish," Schneidervin said.

He said the biologists' goal is twofold: "We want to keep fish from moving above the new barrier to the upper reaches of the West Fork, and we want to keep fish from moving down the diversion tunnel system. This system transfers waters from the West Fork to Current Creek Reservoir, to Strawberry Reservoir and eventually to the Wasatch Front via Diamond Fork."

Whirling disease was discovered in the main stem of the Duchesne River in the late fall of 2006.

"After the discovery, we checked to see just how far it had spread," Schneidervin said. "Our original surveys indicated it had not made it very far above the confluence between the North Fork and the West Fork."

Schneidervin believes a series of beaver dams stopped the upstream spread of fish into the West Fork. Fish sampled a mile below the Vat Diversion did not have the disease.

"With high hopes to contain it at that point, we began the process to get funding and clearance to place a barrier on the West Fork," Schneidervin said. "(Our goal) was to protect a valuable pure-strain population of Colorado River cutthroat trout and to stop the possible spread of the disease through the Vat Diversion."

As the necessary paperwork and work to find sources to fund the barrier progressed, the DWR continued to sample the stream.

"In June 2007, after the spring runoff, we checked the stream again," Schneidervin said. "We were quite surprised to find (that) fish (with) the disease had moved upstream. Cutthroat trout are spring spawners. In their drive to find places to reproduce, (they) defeated the extensive complex of beaver dams."

By the end of the summer, everything was all lined up and ready to go. But before they built the barrier, biologists decided to take one more fish sample. They sampled above and below the proposed barrier site.