Nearly half the young Snake River sockeye salmon being raised at the Oxbow Fish Hatchery near Cascade Locks, Ore., were killed late last month as a result of a damaged raceway valve.
The dead fish are from the 2009 brood year being reared at the hatchery in Cascade Locks, Ore., operated by the Oregon Department of Fish and Wildlife under a federal permit issued to the Idaho Department of Fish and Game.
Sockeye raised at Oxbow are transferred to Idaho annually and released in Sawtooth Basin waters as part of the Snake River Sockeye Salmon Captive Broodstock Program, which was created in 1991. The program was initiated to conserve and rebuild the Redfish Lake sockeye salmon stock in the Sawtooth Valley of central Idaho. Snake River sockeye were listed on Nov. 20, 1991, as endangered under the Endangered Species Act.
The hatchery has a capacity of about 100,000 young sockeye. Hatchery workers on Aug. 25 noticed that fish numbers in an outdoor raceway were just over half what they should have been.
Upon inspection of the raceway, workers found a gap in a valve on the floor of the production raceway, and that fish had been drawn through this gap into a void under the raceway sometime between mid-July and Aug. 23.
They removed valves in lower portions of the raceway and retrieved 1,000 to 2,000 fish -- both live and dead. Engineers are evaluating the site to determine the size of the void, as well as the potential recovery of remaining live fish.
Oxbow got about 100,000 eggs of the 2009 brood year from the Burley Creek Fish Hatchery in Washington in December of 2009. In mid-July, after the eggs had hatched and grown into young fish, they were transferred to outside concrete raceways for final rearing before their release.
The fish numbered 94,826 when they were transferred. After the raceway valve problem, the inventory was 51,609 fish -- a production loss of about 45 percent.
The remaining fish are now in production raceways not associated with the damaged valve.
Meanwhile, an additional 100,000 young salmon of 2009 brood year are being raised at the Idaho Fish and Game Sawtooth Fish Hatchery. The loss at Oxbow accounts for a net reduction of only 25 percent of the 150,000 hatchery produced sockeye projected to be released in May 2011.
While the loss will affect the number of adults returning to the captive brood-stock program in calendar years 2012-2014, it doesn't affect the overall recovery efforts for Snake River sockeye salmon. Other genetically diverse groups of captive brood are being raised in Washington at the Manchester Research Station and Burley Creek Hatchery and in Idaho at the Eagle Fish Hatchery. Current and future egg production will not be limited as a result of this loss at Oxbow.
Since 2004, the Oxbow Fish Hatchery has added to the limited sockeye production of Snake River sockeye salmon with about 100,000 full-term young fish annually.