A genetic evaluation of relatedness for broodstock management of captive, endangered Snake River sockeye salmon, Oncorhynchus nerka

Abstract

The use of captive broodstocks is becoming more frequently employed as the number of species facing endangerment or extinction throughout the world increases. Efforts to rebuild the endangered Snake River sockeye salmon, Oncorhynchus nerka, population have been ongoing for over a decade, but the use of microsatellite data to develop inbreeding avoidance matrices is a more recent component to the program. This study used known genealogical relationships among sockeye salmon offspring to test four different pairwise relatedness estimators and a maximum-likelihood (M-L) relatedness estimator. The goal of this study was to develop a breeding strategy with these estimators that would minimize the loss of genetic diversity, minimize inbreeding, and determine how returning anadromous adults are incorporated into the broodstock along with full-term hatchery adults. Results of this study indicated that both the Mxy and RQG estimators had the lowest Type II error rates and the M-L and RR estimators had the lowest Type I error rates. An approach that utilizes a combination of estimators may provide the most valuable information for managers. We recommend that the M-L and RR methods be used to rank the genetic importance of returning adults and the Mxy or RQG estimators be used to determine which fish to pair for spawning. This approach provides for the best genetic management of this captive, endangered population and should be generally applicable to the genetic management of other endangered stocks with no pedigree.