ROSEBURG, Ore – Oregon Department of Fish and Wildlife biologists announced today that rainbow trout being raised at Butte Falls Hatchery tested positive for the Infectious Hematopoietic Necroses Virus, a virus that is not harmful to humans but can kill fish.
IHNV, a naturally occurring virus was found last week in samples taken from 30,000 rainbow trout fingerlings which hatchery workers then destroyed. The virus was again discovered this week in samples from another group of 125,000 trout fingerlings being reared in several ponds. These fish will currently have a low mortality rate and continue to be raised at the hatchery.
According to Rogue Watershed District Manager Russ Stauff, these rainbow trout are being reared as sentinel fish which ODFW pathologists use to test for the virus.
“Because we discovered IHNV at Butte Falls Hatchery last year, we need to closely monitor fish stocks for the next several years and these fish are being raised for that purpose,” Stauff said. “Our fish health policy requires that a hatchery remain free of the virus for three consecutive years before we stock fish into waters that don’t naturally have the virus.”
Stauff said if there is a need for additional hatchery trout in a waterbody that already is documented as IHNV-positive, ODFW can stock the fish. Local waters that are positive for the virus include the Expo Ponds and the Butte Falls Hatchery public fishing pond.
The fish could also be released in other IHNV-positive waters in the Willamette Valley should they continue to have a low mortality rate.
ODFW’s hatchery and disease policies focus on preventing the spread of pathogens to areas where they do not naturally occur. Hatchery fish that test positive for IHNV cannot be released in any waterbody that does not have the disease.
Officials do not have confirmation of how the virus was transmitted to the hatchery trout, but believe it may have come from wild steelhead spawning above the hatchery. IHNV was found last year in rainbow trout fingerlings, fall chinook stocks intended for the Coquille River, and winter steelhead for the South Umpqua River.