Utilization of Diagnostic SNP Markers for Understanding Genetic Composition of Largemouth Bass Populations in Georgia

Abstract

Efforts to improve recreational fisheries have included extensive movement and stocking of black basses (Micropterus spp.) outside of their native ranges, perhaps none more so than the Florida Bass (Micropterus floridanus; FLMB), valued by anglers for their trophy bass potential. Resource managers need to understand the genetic composition of native populations to assess potential conservation impacts of their decisions, as well as to better estimate the likelihood of stocked fish contributing positively to the fishery. Additionally, monitoring stocking impacts over time necessitates good baseline genetic data. Historically, this information has been lacking in the state of Georgia, with analyses largely limited to sparse allozyme-based assessments. On this basis (as well as morphological characters), Georgia’s bass populations have been regarded as intergrade, resulting from a natural hybrid zone between M. floridanus and its sister species, Largemouth Bass (M. salmoides). Accordingly, utilizing diagnostic SNP marker panels, here we evaluated hybridization rates from over 2,700 individuals in 38 populations across Georgia’s 14 major river basins. FLMB and heterozygous allele frequencies were computed for each individual. Geographic isolation by the naturally occurring Fall Line showed a clear differentiation in average allele percentage and introgression level in populations above the Fall Line compared to those below the fall line. Additionally, several populations below the Fall Line were composed of pure FLMB individuals (n=525) and a novel population of LMB-like individuals was identified in the Altamaha River Basin, contradicting a simplistic view of Georgia bass as entirely intergrade in nature. Our findings should provide a strong foundation for informed bass management decisions in the future, as well as serving to highlight unique, and previously overlooked, aspects of bass genetics in Georgia.