Microsatellite Analysis of Population Structure in Alaska Eulachon with Application to Mixed‐Stock Analysis

• Published in: Transactions of the American Fisheries Society
• Main Authors: Flannery, Blair G., Spangler, Robert E., Norcross, Brenda L., Lewis, Cara J., Wenburg, John K.
• Other Authors: U.S. Fish and Wildlife Service
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Archipelago; Alaska
• Online Access: http://dx.doi.org/10.1080/00028487.2013.790841; https://afspubs.onlinelibrary.wiley.com/doi/pdf/10.1080/00028487.2013.790841

Abstract Estimation of genetic population structure, diversity, and effective population size ( N e ) is important for defining meaningful conservation units and assessing genetic health. Recent conservation concerns in Alaska have highlighted the need for research on Eulachon Thaleichthys pacificus , a species about which relatively little is known. Therefore, genetic variation was assayed at 14 microsatellite loci to investigate the genetic population structure of Alaska Eulachon. This analysis revealed a low degree of genetic divergence ( G ST = 0.005) that is structured by broad‐scale northern and southern geographic regions. Overall, there is a significant correlation between genetic and geographic distances, suggesting that gene flow is geographically restricted and follows an isolation‐by‐distance (IBD) model. However, closer analysis reveals an absence of IBD within regions and that gene flow is primarily restricted by the geographic distance between regions, a pattern that better approximates the hierarchical island model. Gene flow is likely restricted between regions by a biogeographical barrier (i.e., the Alexander Archipelago). Alaska Eulachon have high levels of genetic diversity and relatively large N e estimates of 3,535 and 2,823 for the northern and southern regions, respectively, although a large variance in reproductive success is likely responsible for a low N e / N ratio. The observed genetic divergence suggests that it would be advantageous to manage the two regions separately to maintain productivity and evolutionary potential for Eulachon. Mixed‐stock analysis (MSA) of simulated and known‐origin mixtures supports the feasibility of regional stock separation. The northern and southern regions had MSA accuracies that were near or greater than 90% when fish from a single region comprised the mixtures. Further population structure may be present within regions, but additional analyses of collections across sampling years are necessary to clarify the microevolutionary processes.