SALEM - The Oregon Department of Fish and Wildlife announced today it will euthanize approximately 50,000 rainbow trout being held at Leaburg Hatchery during the next few days because they have contracted, or been exposed to, an incurable disease. Healthy fish will be released ahead of schedule to prevent them from also contracting the infection.
These actions are in accordance with ODFW's Fish Health Management Policy, which prescribes the implementation of fish health strategies to reduce disease agents and fish losses in Oregon.
The trout being euthanized have been raised in a pond where fish were diagnosed last week with the infectious hematopoietic necrosis (IHN) virus. IHN is a naturally occurring virus that initially attacks the blood-forming tissues of the kidney. External symptoms include lethargy, darkening of the skin and hemorrhaging at the base of the fins. Past experience shows that hatchery fish losses can increase dramatically from this disease, which has no known treatment.
Staff from the Eugene-area hatchery are working with fish pathologists and other ODFW staff to minimize the chance of IHN recurring. Hatchery staff will clean the fish rearing ponds where the infection occurred and plan to take steps necessary to prevent the virus from entering the hatchery via the hatchery water source.
The infected trout had been destined for release in Willamette Valley waterbodies this fall. ODFW is evaluating the potential impact on fall fisheries of this IHN outbreak. The rainbow trout will be euthanized using MS-222 (tricaine methane sulfonate) a chemical in the novocaine family of drugs approved by the American Veterinary Medical Association's panel on euthanasia as an acceptable and humane way of euthanizing fish not used for human consumption. The fish will be frozen and sent to a landfill to contain the spread of the disease.
ODFW fish pathologists will continue to sample fish at the hatchery. If IHN infects more trout, additional steps will be taken to contain the disease. Leaburg Hatchery also was forced to euthanize trout in spring 2003 due to IHN. Leaburg Hatchery is the largest trout hatchery on the west coast, and reared more than a million rainbow trout this year. The hatchery's operations are funded by the U.S. Army Corps of Engineers.