PUTTING THE RED BACK IN REDFISH LAKE - TWENTY YEARS OF CAPTIVE BROODSTOCK PROGRESS TOWARDS SAVING THE PACIFIC NORTHWEST'S MOST ENDANGERED POPULATION OF SALMON

Thomas A. Flagg*, and Paul A. Kline
NOAA Fisheries, Northwest Fisheries Science Center, Manchester Research Station, PO Box 130, Manchester, WA 98353. E-mail: tom.flagg@noaa.gov

 

In November 1991, Snake River sockeye salmon (Oncorhynchus nerka) were listed as endangered under the U.S. Endangered Species Act (ESA). These fish are one of the most depleted populations of salmonids in the world, with the last known remnants returning to Redfish Lake in the Sawtooth Valley in central Idaho. Only 16 adult fish total (11 males and 5 females) returned to Redfish Lake during the decade after ESA listing, all were taken into captivity for broodstock. The culture program for Redfish Lake sockeye salmon has resulted in the production of over 10,000 adult captive descendants from these 16 wild fish. The genetic focus of the program and adherence to various central tenets of conservation aquaculture has enabled program managers to retain approximately 95% of the original founding genetic variability. Overall, the Redfish Lake sockeye salmon captive broodstock effort has experienced great production success. Survival to the eyed-stage of development usually exceeds 80%, while fry-to-maturation survival is also in the 80% range. Over 1.5 million captive-reared fish have been released as pre-smolts, 1.5 million as smolts, 1.0 million planted as eyed-eggs, and 5,500 released as pre-spawning adults to Sawtooth Valley lakes and tributary streams. Since the first program-produced adult fish started returning from the ocean in 1999, over 6,500 adults have returned to collection sites in the Sawtooth Valley. Average smolt-to-adult return from the ocean for anadromous sockeye salmon produced from juveniles released as smolts were almost 2.3 times greater than average rates for adults produced from pre-smolt releases (0.48% vs 0.21%). Average smolt-to-adult return for fish produced from natural spawning events were over 2.7 times higher than average rates for adults produced from smolt releases (1.30% vs 0.48%) and about 6.2 times higher than rates for fish released as pre-smolts. This outcome is a critically important as it demonstrates the potential for the population to become self-sustaining and effectively address draft recovery objectives. A new hatchery (Springfield) has been constructed in Idaho to produce 1 million smolts that should result in an average of 5,000 adults returning from the ocean annually. Models have been developed to transition the program from the captive broodstock phase through re-colonization and local adaption phases. This planning balances the amount of natural-origin spawners taken into the broodstock with the proportion released to the habitat for natural spawning and provides specific biological trigger points that should lead to phasing out both the captive broodstock and, ultimately, all hatchery intervention components. It seems certain that the use of captive broodstock technology and the steps described above have put the population on the road to recovery.