Hydrogeographic Vicariance Determines the Genetic Structure of Northwestern Walleye Populations

Abstract

Walleye Sander vitreus is one of the most important freshwater commercial and sport fishes in western Canada. It is an intensively managed species that is under considerable harvest pressure, yet little is known about the patterns of genetic variation and diversity of walleyes between connected water bodies and among river basins in this region. We examined the genetic variation of walleyes from 12 lakes in five different river basins of northern Alberta. Each lake contained a genetically distinct walleye subpopulation nested within a larger population of the river basin in which the lake was situated. Differentiation between subpopulations varied (F _ST = 0.05–0.29) and exhibited a broad-scale isolation-by-distance pattern. Patterns of genetic divergence aligned closely with the current hydrogeographical landscape, as subpopulations in the same river basin were more similar than those in different river basins. The clear and distinct pattern of genetic structure is likely to have been generated and maintained by historical vicariance and natal philopatry. Because walleye populations are so clearly genetically structured by hydrogeography in western Canada, these data can be used to monitor population status, assess stocking programs, delineate management units, and enable forensic enforcement of harvest restrictions in this region.

Received July 4, 2011; accepted December 6, 2011.

ACKNOWLEDGMENTS

Financial support was provided by Alberta Sustainable Resource Development, the Cumulative Environmental Management Association (CEMA), the Alberta Conservation Association (ACA), and the Department of Biological Sciences at the University of Alberta. The authors are greatly appreciative to M. Sullivan for his input, advice, knowledge, and enthusiasm for this project. The authors also thank W. Tonn and L. Foote for their comments and advice. Y. Laurent drafted the map of the population locations. Thanks are also extended to D. Latty, O. Watkins, S. Spencer, C. Davis, J. Walker, G. Sterling, D. Watters, and numerous other fisheries biologists and wildlife officers across Alberta for collecting the fin samples used in this project.