Biologists build barrier, remove fish

Work continues to contain whirling disease in the Duchesne River

DUCHESNE — Biologists are hoping that constructing a fish barrier and removing fish from 1 1/2 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.

Biologists remove fish killed by the rotenone treatment. It's important to remove these fish—a fish that has whirling disease can contain hundreds of thousands of whirling disease spores.

Photo by Ron Stewart

"We don't know if we can completely stop the spread of whirling disease," says 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, UDWR 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 says.

Schneidervin says 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."

Discovery

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 says. "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 says. "[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. "

Getting past the dams

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

"In June 2007, after the spring runoff, we checked the stream again," Schneidervin says. "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."

Another discovery

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 says. "We cancelled 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 says because only one fish tested positive, the group felt they could still slow the spread of whirling disease upstream or through the diversion. "The proposed barrier site was moved about 1 1/2 miles above the diversion to a narrow spot upstream," Schneidervin says. "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 says. "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."

Barrier built

Division of Wildlife Resources biologists release rotenone into the West Fork of the Duchesne River.

Photo by Ron Stewart

To beat the spring floods this year, UDWR 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 says. "[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."

Anglers—your help is needed

Whether whirling disease spreads in the future depends on many factors, few of which are in the UDWR'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 says. "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."

"With the new, exotic threats to our waters, such as whirling disease, quagga mussels, zebra snails and even plants, anglers need to learn a whole new way of dealing with their catch and equipment."

Tips

Schneidervin says you can do several things to prevent the spread of whirling disease:

• Do not transport fish from one water to another and clean the fish in a different water. Also, if you're fishing a stream, don't move fish from one part of the stream to another area on the same stream.
• After cleaning your fish, dispose of their parts, especially their heads, in a landfill.
• If a landfill isn't available, clean the fish and dispose of their parts by burying them deep, a long way away from a water.
• Clean all of your equipment thoroughly and dry it after every use.

New way of thinking

"Fishing is a great sport, and it can supply an excellent meal," Schneidervin says. "We just need to develop a new way of thinking and dealing with some new, serious threats to [fishing]."