Human impacts on Great Lakes walleye Sander vitreus gene flow,
diversity, and local adaptation
Abstract
Artificial propagation and wild release may influence the genetic
integrity of wild populations. This practice has been prevalent in
fisheries for millennia and is often termed “stocking”. In the
Laurentian Great Lakes, walleye populations faced declines from the
1950s to the 1970s, prompting extensive stocking efforts for
restoration. By the mid-2010s, walleye populations showed signs of
recovery, but the genetic legacy of stocking on population structure at
the genomic level remains unclear. Using a dataset of 45,600
genome-aligned SNP loci genotyped in 1,075 walleye individuals, we
investigated the genetic impacts of over 50 years of stocking across the
Great Lakes. Natural geographic barriers shaped walleye population
structure, but pairwise comparisons revealed changes in genetic
structure due to stocking from non-native sources also significantly
contribute to population structure. Admixture between Lake Erie walleye
and walleye from the re-populated Tittabawassee River indicate that
stocking may have re-distributed putatively adaptive alleles around the
Great Lakes. Genome scans identified FST outliers and evidence of
selective sweeps, indicating local adaptation of spawning populations is
likely. Notably, one genomic region showed strong differentiation
between Muskegon River and walleye from the Tittabawassee River which
was re-populated by Muskegon Strain walleye, suggesting admixture and
selection both impact the observed genetic diversity. Overall, our study
underscores how artificial propagation and translocations can
significantly alter the evolutionary trajectory of populations. The
findings highlight the complex interplay between stocking practices and
genetic diversity, emphasizing the need for careful management
strategies to preserve the genetic integrity of wild populations amidst
conservation efforts.