AFTON -- The parasite causing whirling disease has been found in brood-stock cutthroat trout in a pond near the Auburn Fish Hatchery near Afton. The outside pond is isolated from and uses a different water supply than the hatchery itself where fish are hatched and grown for release.
Game and Fish Hatchery Supervisor Steve Sharon said the discovery will complicate hatchery operations but it does not represent a threat to the other fish production facilities or fish populations in the state.
“The pond where the parasite has been found is located within the stream channel of Webster Creek,” Sharon said. “The raceways and troughs at the Auburn Hatchery itself are fed from a spring that is entirely separate from the surface system. No sign of the disease has been found in any fish raised at the hatchery.”
The brood pond is located downstream from the hatchery discharge. The parasite was found in Webster Creek upstream from the brood pond earlier this spring.
Dave Money, G&F fish pathologist, discovered a low level of infection in the gill arches of the brood fish Aug. 16. The fish were collected during a routine July inspection.
Money said the fish, which are used for egg production, were infected as mature fish and therefore show no outward signs of the disease. The parasite attacks growing cartilage only and the only new cartilage in mature fish is in the gill arches. Fish eggs cannot carry the disease.
Young fish with growing skeletal cartilage are much more susceptible to the disease. They are also the only fish to show symptoms and suffer the effects of the disease, Money said. Mature fish can be carriers but will not die from the disease.
Money said all fish raised in Wyoming hatchery raceways since 1988 have been checked for the disease and no fish have tested positive. “We started a very aggressive testing program when the disease was first discovered in neighboring states,” he said. “We test hatcheries that might be at risk for the disease two times every year and all other hatcheries once a year. Whirling disease has never been found in any of these tests on production fish.”
State Fisheries Chief Mike Stone said the discovery will cost the G&F more money and will reduce the flexibility of the hatchery system, but he is adamant that it will not affect the spread of the disease.
“This discovery will not affect the quality of fish we raise here in Wyoming,” he said.
“We have not and we will not stock fish which are infected with whirling disease.”
“We believe we can manage around this situation with increased cost to the department, increased effort by all fisheries personnel, and a loss of flexibility,” Stone said. “This means it will take more effort and it will cost more money to provide the same level of fish production.”
Stone said the ultimate solution to the problem would be to develop facilities for brood stocks that do not rely on dirt ponds or on water from a creek or other surface water source. Such improvements could cost in the neighborhood of $600,000.
Officials also plan to adjust procedures in moving eggs from the brood pond to the hatchery to insure that no contaminated material might be transferred with the eggs. Precautions include additional treatment of the eggs and inspection of young fish.
Whirling disease attacks the cartilage of young trout causing skeletal deformities and sometimes a discolored black tail. It is potentially fatal to young trout and has resulted in significant population declines in wild fish in neighboring states. Current data indicate Wyoming has experienced no such population declines.
The disease has been found in Wyoming in the North and South Platte, the Salt, the South Fork of the Shoshone, and the upper Green river drainages. Young rainbow trout are at greatest risk but other trout species can also be affected.
The parasite has a complex two-host life cycle involving trout and a common bottom-dwelling tubifex worm.
The G&F follows strict procedures for cleaning and disinfecting all equipment. Anglers can help by following these similar guidelines:
- Please don’t throw fish entrails or other by-products into any body of water or drain.
- Thoroughly wash mud from vehicles, boats, trailers, waders, boots, fishing equipment and anything that else that could have come in contact with the streambed mud that harbors whirling disease spores and worms.
- Drain boats, equipment, coolers, live bait wells and any other water which could hold the parasite.
- Never transport aquatic plants and clear all weeds from equipment after every use.
- Please don’t transport any fish from one stream or lake another.