Genetic inventory of anadromous Pacific salmonids of the Elwha River prior to dam removal

Abstract

We genetically characterized seven species of Pacific salmonids in the Elwha River and in selected neighboring rivers prior to the impending removal of two dams. Monitoring the genetics of recolonization of the watershed by remnant native, hatchery, and/or adjacent watershed populations is a critical element to further our understanding of ecosystem restoration. By pooling data from independent studies, we assessed intraspecific diversity for pink salmon (Oncorhynchus gorbuscha), chum salmon (O. keta), coho salmon (O. kisutch), sockeye salmon (O. nerka), Chinook salmon (O. tshawytscha), rainbow trout (O. mykiss) and bull trout (Salvelinus confluentus). Levels and patterns of genetic variability within and among collections were evaluated at 6-15 microsatellite (mSAT) loci per species. Each species had 3-8 loci with 20 or more alleles. In all species, an Elwha collection was statistically different from one or more nearest-neighbor population. In addition, the native in-river collections of Chinook salmon and steelhead (anadromous rainbow trout) were distinguishable from existing in-river hatchery stocks. In most species, Elwha populations contained similar levels of genetic diversity as observed in neighboring river systems. In O. mykiss, variability at an evolutionarily adaptive major histocompatibility complex (MHC) gene paralleled the mSAT variation. Given the various levels of distinctiveness of Elwha populations, we discuss the use of these data as a genetic ruler to manage and monitor the genetic aspects of recolonization of the Elwha River, and the importance of tissue archives for new genetic techniques.