Ella Bowles

Concordia University
Rapid body size reduction and genomic change associated with harvesting within two generations in wild walleye populations

Ella Bowles*, Kia Marin, Pamela Macleod, Dylan J. Fraser

Whether or not exploited fishes experience evolutionary changes and the rate at which they occur will impact the amount of time available to mitigate damage to stocks. While there is substantial evidence for phenotypic changes in exploited fishes, the genetic evidence required to detect evolutionary change is seldom provided alongside phenotypic evidence, and the number of generations needed for those evolutionary changes is not well understood. We assessed changes in body size and genomic metrics in three exploited walleye (Sander vitreus) populations and a fourth less-exploited reference population over a 15-year period in Mistassini Lake, Quebec. Using >9000 SNPs, genetic metrics included population structure, neutral genetic diversity, effective population size and signatures of selection. Smaller body size, changing population structure and signatures of selection between historical and contemporary samples reflect coupled phenotypic and genomic change in the three exploited populations, while no change occurred in the reference population. This evidence is consistent with fisheries induced evolution within two-generations in the southern walleye populations, suggesting that in cases of exploitation, management action must be taken quickly.