Genetic Marking of Sockeye Salmon Anadromous Returns in the Sawtooth Valley Lakes, Idaho

The Snake River Sockeye Salmon population was listed as endangered under the Endangered Species Act in 1991 when only a handful of fish returned the prior year.  In that same year, a captive broodstock program was inititated to maintain the population and prevent species extinction.  The goals of the program were twofold:  1) Conserve the population in the short-term by reducing demographic, genetic, and environmental risks that could lead to extinction and 2) Re-introduce and re-build the Snake River Sockeye Salmon population.  Progeny are reintroduced to the Sawtooth Valley Lakes in Idaho at different life-history stages using a variety of release options including: 1) eyed-egg releases to lake incubator boxes, 2) pre-smolt releases direct to the lakes, 3) smolt releases to outlet streams and to the upper Salmon River, and 4) pre-spawn adult releases direct to the lakes. Generally, the pre-smolts and smolts are marked with different tags or clips but these marks can lead to reduced survival and there was no way to differentiate natural fish from those returning from an eyed-egg release strategy.  Using 13 microsatellite loci and parentage analyses, every fish in the program was genotyped and 95% of the returning fish could be assigned back to a release strategy.   In addition, important measurements such as the number of recruits per spawner, effective population size and genetic diversity could be calculated and used to evaluate the different release strategies.  This information was used to not only determine the best direction for recovery but also to help with broodstock selection. Genetic marking has shown to be a valuable tool for the monitoring and evaluation of many conservation hatchery programs and will provide invaluable information to this program.