Human Impacts on Great Lakes Walleye Sander vitreus Structure, Diversity and Local Adaptation

Area of Science:

• Population Genetics
• Conservation Genetics
• Fisheries Management

Background:

• Walleye populations in the Laurentian Great Lakes experienced declines, leading to extensive stocking efforts for restoration.
• The long-term genetic consequences of these stocking practices on wild walleye populations at the genomic level were not well understood.

Purpose of the Study:

• To investigate the genetic impacts of over 50 years of walleye stocking on population structure and diversity across the Great Lakes.
• To understand how artificial propagation and translocations influence the evolutionary trajectory of wild fish populations.

Main Methods:

• Genomic analysis of 1075 walleye individuals using 45,600 genome-aligned single nucleotide polymorphism (SNP) loci.
• Population structure analysis incorporating natural geographic barriers and stocking history.
• Genome scans to identify F_ST outliers and selective sweeps indicative of local adaptation.

Main Results:

• Walleye population structure is shaped by both natural barriers and non-native stocking sources.
• Evidence of admixture between distinct walleye populations (e.g., Lake Erie and Tittabawassee River) due to stocking, potentially redistributing adaptive alleles.
• Identification of genomic regions under selection, suggesting local adaptation in spawning populations, with one region showing differentiation linked to stocking strains.

Conclusions:

• Artificial propagation and translocations significantly alter the genetic integrity and evolutionary path of wild fish populations.
• Stocking practices create a complex interplay with natural population genetic diversity, necessitating careful management.
• Findings emphasize the need for strategic management to preserve genetic diversity and integrity in conservation efforts.