03-02-2003, 06:56 PM

Contact: Dennie Hammer (307) 527-7125
For Immediate Release



CODY – The microscopic parasite Myxobolus cerebralis, that infiltrates the head and spinal cartilage of fingerling trout and causes whirling disease, was discovered in fish sampled from and the Clark’s Fork River and its tributary Bennett Creek this winter.

The parasite was detected after examining rainbow, Yellowstone cutthroat and brown trout, and mountain whitefish, plus several species of small, young of the year fish. Only some of the young of the year fish and rainbow trout were infected.

According to Clark’s Fork Hatchery Superintendent Dave Miller, neither the parasite nor the disease is present in the hatchery. Hatchery fish are inspected for whirling disease twice a year; the inspection performed last January and August had negative results.

Finding the parasite in the drainages near the hatchery is a concern, but not a threat at the present time. “The water we use in our hatchery comes from a closed system, that is, from several underground springs,” Miller said. “The water is piped directly to the facility. Also, the raceways are concrete which allows for proper cleaning which prevents whirling disease spores from establishing.”

However, to minimize the possibility of the parasite being unintentionally introduced into the hatchery system precautionary measures are being implemented. “Many hatchery visitors are anglers that stop by as they fish the Clark’s Fork River,” he said. “Although we welcome visitors to our hatchery, visitors will not be allowed to wear any type of hip boot, wader or wading shoe, nor will they be allowed to carry fishing equipment while walking within the facility.”

Miller also plans to surround the facility with a security fence to restrict unauthorized access.

Cody Regional Fisheries Supervisor Steve Yekel, is concerned about the discovery of the disease, but does not feel that it is a major problem at this point. “It will be very important to continue to monitor fish in and around the hatchery to keep track of the movement of the disease,” he said.

Yekel added that the discovery of the disease would not affect fish management in these waters at this time. Sampling to determine the degree the organism may have spread in the drainage is scheduled for 2003.

Yekel said anglers could help minimize the spread of the disease by taking a few precautions. “Anglers should take the time to clean the mud from their boots, waders, rafts, boats and trailers before moving to their next fishing site,” he said. He added that the parasite produces myxospores which are virtually indestructible and which can survive in a dormant form for up to 30 years in water and mud. Because an infected fish can harbor tens of thousands of the myxospores he also recommends discarding skeletal parts and fish entrails in dry waste that goes to a landfill when possible. Anglers should not discard these parts in the water where the fish was caught, nor should they be disposed of in a kitchen disposal. Whirling disease myxospores can survive most wastewater treatment systems.

Yekel also stated that whirling disease is slowly drifting downstream in the South Fork Shoshone River. In 1996, whirling disease was discovered in fish samples taken about one mile above the confluence of Boulder Creek and the South Fork. Fish samples collected in 2002 indicate that the parasite has moved downstream from that location about 6 miles, nearing the confluence of Ishawooa Creek with the South Fork. The disease was not found in samples collected several miles upstream of the original 1996 infection site.