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.

"(The fish) came back positive (for the disease)," Schneidervin said. "We canceled the construction of the barrier. We then (sampled) above the Vat Diversion. One fish from a sample of 54 came back positive. That really sparked a discussion (about where to place the diversion dam)."

Schneidervin said because only one fish tested positive, the group felt it could still slow the spread of whirling disease upstream or through the diversion.

"The proposed barrier site was moved about 11.2 miles above the diversion to a narrow spot upstream," he said.

"We also decided to remove fish between the two structures once the new barrier was completed.

As a final measure, sentinel fish in cages were placed in the stream at the Vat Diversion. "(Sentinel fish were also placed) near the new barrier site to verify the single positive fish from the earlier sample," Schneidervin said. "The results (turned up) negative for the 120 fish tested in the fall and the 66 tested in the spring. With only one fish (testing positive among the) 240 fish tested, there is a good possibility that the disease may not be spreading into this upper section of the stream."

To beat the spring floods this year, DWR heavy equipment crews plowed through several feet of snow and cleared some massive drifts to open the road. Then they moved huge rocks into place to construct the fish barrier. A week later, crews went in, treated the stream with rotenone and then removed the fish that the rotenone killed between the two barriers.

"We didn't want to leave any fish carcasses in the stream as one fish could carry hundreds of thousands of whirling disease spores just in its head (alone)," Schneidervin said. "(That's the likely way that) whirling disease got to the Duchesne River in the first place. Research indicates the disease is likely being moved by someone taking a fish from a contaminated water and, after cleaning it, throwing the head and guts into another stream or lake."

Whether whirling disease spreads in the future depends on many factors, few of which are in the DWR's control.

"We've put the structures in place. Now, slowing the spread of disease depends a bit on luck and cooperation, especially (from) anglers," Schneidervin said. "The experts generally agree (that anglers are to blame for) the recent spread of the disease.

"Some spread is likely from anglers not cleaning their gear, such as waders, after fishing in a contaminated stream. A greater threat is anglers moving fish and fish parts from one place to another.