Microsatellites Reveal Population Substructure of Klickitat River Native Steelhead and Genetic Divergence from an Introduced Stock

Abstract

Determining fine‐scale genetic diversity and structure is critical for the conservation and management of populations, especially those under heavy anthropogenic influence. We analyzed 446 individuals at nine microsatellite loci to determine the local population structure of naturally produced steelhead Oncorhynchus mykiss and genetic differentiation from introduced hatchery strain steelhead in the Klickitat River of the Pacific Northwest. We detected significant genetic structure among steelhead in various tributaries to the Klickitat River; the most divergent population was located above a waterfall that acts as a partial upstream migration barrier (average pairwise FST = 0.13; P < 0.0001). Analysis of mixtures indicated an estimate of six to seven genetically distinct populations of naturally reproducing steelhead in this river system. The hatchery strain appears to remain genetically distinguishable from native stocks (average pairwise FST of 0.078 with P < 0.0001), as only 4.0% of naturally produced steelhead had their most likely assignment to the hatchery strain. These results indicate that the genetic integrity and variation of native Klickitat River steelhead have been maintained despite repeated hatchery introductions and that the potential is high for restoring this threatened population. Further, this study suggests that hierarchical analyses of mixtures to identify distinct populations in a watershed are a valuable method for directing management of reproductively isolated populations.

Population structure and partial anadromy in Oncorhynchus mykiss from Kamchatka: relevance for conservation strategies around the Pacific Rim

“…Expected heterozygosity in our study populations (0.24-0.54) was low compared with microsatellite studies of O. mykiss from other regions. For example, expected heterozygosity based on previous microsatellite studies ranged from 0.55-0.59 in Alaska (Olsen et al 2006), 0.51-0.87 in British Columbia (Heath et al 2001;Hendry et al 2002;Heggenes et al 2006), 0.68-0.86 in Washington (Ardren & Kapuscinski 2003;Narum et al 2006) and 0.62-0.79 in California (Aguilar & Garza 2006). We were able to compare single-locus measures of observed heterozygosity from these studies for five of our 10 loci.…”

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…There is correlative ) and experimental evidence that temperature influences residency through effects on energy allocation, with cooler temperatures allowing for greater accumulation of lipids that are limiting to maturation Sloat and Reeves 2014). Water temperature may also help explain why residents were more common in streams with high summer flows (Courter et al 2009) and at higher elevations within a river network (Cramer et al 2003;Narum et al 2006), all of which are often interconnected. Data on water temperature in relation to stream flow and altitude could answer the following questions: What are the effects of higher summer flows and cooler temperatures on growth and lipid storage and, in turn, residency and anadromy?…”

A Genetic and Phenetic Baseline before the Recolonization of Steelhead above Howard Hanson Dam, Green River, Washington

“…In comparison, average H e over 19 generations of steelhead at Snow Creek, Puget Sound, was 0.90 (Seamons et al 2007), whereas seven rainbow trout and steelhead collections in the Elwha River had a mean H e of 0.77 (0.67-0.82) and mean A r of 7.6 (5.5-9.6) over 15 loci (Winans et al 2008). Expected heterozygosity and allelic richness in the Walla Walla and Klickitat drainages in the mid-Columbia River averaged 0.79 and 0.805 (H e ) and 14.1 and 9.5 (A r ), respectively (Narum et al 2004;Narum et al 2006). Inland populations of O. mykiss in the Spokane River…”

“…Other work indicates steady but low levels of gene flow from rainbow trout into a sympatric steelhead population depending upon, among other things, the abundance of the steelhead returns (Araki et al 2007b). When found in allopatry, moderate levels of genetic divergence of these two life history types have been reported at DNA markers (Docker and Heath 2003;Narum et al 2006;Deiner et al 2007). Phenotypic variation in morphological and life history characters has been reported in isolated rainbow trout populations (Northcote and Hartman 1988;Keeley et al 2005).…”