**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract for this completion report are provided below.  For a copy of the full completion report, please contact the author via e-mail at brian.sloss@uwsp.edu . Questions? Contact the GLFC via email at frp@glfc.org or via telephone at 734-662-3209.**

Delineation of natural boundaries of MuskELLUNGE in the Great Lakes and THE effects of supplementation on genetic integrity of Remnant stocks

Brian L. Sloss², Patrick Hanchin³,John Farrell⁴, Kevin Kapuscinski⁵, Loren Miller⁶, Kim Scribner⁷, Chris Wilson⁸

² College of Natural Resources, 800 Reserve St., University of Wisconsin-Stevens Point, Stevens Point, WI 54481;

³ Michigan Dept. of Natural Resources, 96 Grant Street, Charlevoix, MI 49720;

⁴ State Univ. of New York, College of Environmental Science and Forestry, 250 Illick Hall, 1 Forestry Drive, Syracuse, NY 13212;

⁵ College of Arts and Sciences, CRW225, Lake Superior State University, 650 W. Easterday Ave., Sault Ste. Marie, MI 49783;

⁶ Minnesota Dept. of Natural Resources, Univ. of Minnesota, 200 Hodson, 1980 Folwell Ave., St. Paul, MN 55108;

⁷ Michigan State Univ., 13 Natural Resources Building, East Lansing, MI 48824;

⁸ Ontario Ministry of Natural Resources, Trent Univ., Peterborough ON, Canada K9J 7B8

November 2017

ABSTRACT:

Muskellunge (Esox masquinongy) are important apex predators that support numerous recreational fisheries throughout the Great Lakes region. Declines in muskellunge abundance from historical overharvest and environmental degradation have threatened the viability of many populations and prompted significant restoration efforts that often include stocking. The goal of our study was to investigate contemporary population structure and genetic diversity in 42 populations of muskellunge sampled across the Great Lakes region to inform future management and supplementation practices. We genotyped 1,896 muskellunge (N = 10-123/population) at 13 microsatellite loci. The greatest genetic variation was between populations of Great Lakes origin and populations of Northern (inland) origin, with both groups also exhibiting significant substructure (overall F_ST = 0.23). Genetic structure was generally correlated with geography; however, we only found marginal evidence of isolation by distance, likely due to high genetic differentiation among proximate populations. Measures of genetic diversity were moderate across most populations, but some populations displayed low diversity consistent with small population sizes or historical bottlenecks. Many of the populations studied displayed evidence of historic introductions and supplemental stocking, including the presence of individuals with primarily non-native ancestry as well as interlineage hybrids. Our results suggest that the historic population structure of muskellunge is largely intact across the Great Lakes region, but also that stocking practices have altered this structure to some degree. We suggest that future supplementation practices use local sources where possible, and incorporate genetic tools including broodstock screening to ensure that non-native muskellunge are not used to supplement wild populations.