43,000 Diseased Salmon Smolts Killedby Staff
The Idaho Statesman, June 6, 2002
CASCADE LOCKS, Ore. -- The Oregon Department of Fish and Wildlife has killed more than 43,000 sockeye salmon smolts infected with an incurable virus.
The fish were reared at Bonneville Hatchery for the Idaho Department of Fish and Game.
The juvenile sockeye, destined to replenish low populations in Idaho´s Redfish Lake, had the IHN virus, which is found throughout the Columbia River.
The Idaho department requested the kill to prevent other fish from getting the disease.
The smolts were offspring of fish listed as endangered under the federal Endangered Species Act.
The virus attacks the blood-forming tissues of the kidney. Fish pathologists said 80 percent to 90 percent of the fish would have been dead within six weeks.
“We´ve tested thousands of fish in captive brood programs over the past 11 years and have never found the virus before,” said Keith Johnson, an IDFG pathologist. “Destroying these fish is a disappointment, but we have to make sure that no virus-positive fish are incorporated into the captive brood program.”
The sockeye smolts probably got the disease from adult steelhead that entered Tanner Creek from the Columbia River, pathologists said.
The smolts were killed using a chemical in the Novocain family of drugs. The fish were frozen and will be sent to a landfill to contain the spread of disease.
Press Release from Oregon Department of Fish & Wildlife
Diseased Sockeye Euthanized at Bonneville Hatchery
CASCADE LOCKS -- Oregon Department of Fish and Wildlife (ODFW) announced that more than 43,000 sockeye salmon smolts reared at Bonneville Hatchery for the Idaho Department of Fish and Game (IDFG) were euthanized today due to an incurable virus.
The juvenile sockeye, destined to replenish critically low populations in Idaho's Redfish Lake, contracted the IHN (infectious hematopoietic necrosis) virus, which is found throughout the Columbia River system.
The National Marine Fisheries Service (NMFS) directed ODFW to take today’s action after IDFG requested the fish be euthanized to prevent other fish from contracting the non-treatable disease. ODFW operates the sockeye rearing program as an agent for NMFS. The smolts were offspring of fish listed as endangered under the federal Endangered Species Act (ESA).
A cooperative captive brood program is in place to enhance wild populations using conservation hatcheries in Idaho, Oregon and Washington. Although the loss of the sockeye smolts will reduce the number of adults returning from the ocean in 2004, the Bonneville-reared fish comprise only one component of the sockeye restoration program for central Idaho. Out-migrating smolts from Redfish and other central Idaho lakes are now estimated at 68,000 in 2002.
Testing for pathogens and disease occurs regularly in the captive brood rearing cycle from egg to release as smolts. About 70,000 disease-free eggs were transferred to Bonneville Hatchery for rearing in January 2001 from NMFS's Manchester Research Station in Washington's Puget Sound area and from IDFG's Eagle Hatchery near Boise. Testing at Bonneville detected IHN infection in late April, 2002 just before the smolts were scheduled for transport to Idaho for release. Daily losses since early May reduced the number euthanized Tuesday to about 43,000 smolts.
"We've tested thousands of fish in captive brood programs over the past 11 years and have never found the virus before," said Keith Johnson, pathologist for IDFG who works closely with ODFW. "Destroying these fish is a disappointment, but we have to make sure that no virus-positive fish are incorporated into the captive brood program."
According to Oregon fish pathologists familiar with IHN, it is likely that 80 to 90 percent of the remaining fish would have died within the next six weeks. IHN 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. The most likely source of the disease was from adult steelhead carrying IHN that entered Tanner Creek from the Columbia River and swam above the hatchery water intake. Tanner Creek supplies water to the hatchery rearing ponds. Testing found that no other juvenile salmon or steelhead species currently being reared at the Bonneville facility have contracted the virus.
The sockeye smolts were killed using MS222 (tricaine methane sulfonate), a chemical in the novocaine family of drugs approved by the American Veterinary Medical Association's (AVMA) Panel on Euthanasia as an acceptable and humane way of euthanizing fish not used for human consumption. The fish were frozen and will be sent to a landfill to contain the spread of the disease.
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