Loss of Genetic Integrity in Hatchery Steelhead Produced by Juvenile‐Based Broodstock and Wild Integration: Conflicts in Production and Conservation Goals

Abstract

AbstractWe examined whether a supplementation program for steelhead Oncorhynchus mykiss in southwestern Washington could produce hatchery fish that contained genetic characteristics of the endemic population from which it was derived and simultaneously meet a production goal. Hatchery fish were produced for three consecutive years by using broodstock comprised of endemic juveniles that were caught in the wild and raised to maturity, and then the program transitioned to an integrated broodstock comprised of wild and hatchery adults that returned to spawn. Importantly, some auxiliary conservation‐based husbandry protocols were attempted (i.e., pairwise mating between males and females) but not always completed due to insufficient broodstock and conflict between production and conservation goals. The hatchery met production goals in 6 of 9 years, but wild‐type genetic integrity of hatchery fish was degraded every year. Specifically, we analyzed 10 microsatellites and observed a 60% reduction in the effective number of breeders in the hatchery (harmonic mean of hatchery, Nb = 45, compared with the wild, Nb = 111). Hatchery fish consequently displayed reduced genetic diversity and large temporal genetic divergence compared with wild counterparts. To ensure the benefit of conservation‐based husbandry, spawning protocols should be based on scientific theory and be practical within the physical and biological constraints of the system. Finally, if conservation issues are considered to be the most important issue for hatchery propagation, then production goals may need to be forfeited.Received November 8, 2013; accepted February 19, 2014