Genetic assessment of lake sturgeon stocking practices in two Lake Superior tributaries

Lake sturgeon were extirpated throughout much of their historic range in the early 1900s due to overharvest, habitat degradation, and reduced water quality. Interagency management plans have worked to identify historic locations and remnant populations suitable for stocking and habitat remediation to rebuild self-sustaining populations of lake sturgeon within their historic range. The St. Louis River population was extirpated in the early 1900s until lake sturgeon were stocked from 1983-2000 from two different source populations (Wolf River, Sturgeon River). Natural reproduction was confirmed in 2011 and F1 generation larvae were collected in 2017 (n = 41) and 2019 (n = 51). Genetic assignment testing using 12 microsatellite loci identified first generation Wolf River and Sturgeon River offspring. However, the offspring sampled were produced by a small number of adult spawners (2017: Nb = 15 95% CI 9-31 and 2019: Nb = 16 95% CI 9-31) and had reduced allelic richness when compared to Wolf River individuals (p \u3c 0.05), indicating the founder effect has limited genetic diversity within the first years of reproduction. Lake sturgeon have been stocked at the Ontonagon River since 1998. In 2017, a total of 759 lake sturgeon were stocked in the Ontonagon River. Of these offspring, 84 were produced via partial factorial mating from gamete collections of Sturgeon River fish; the remaining 675 offspring were naturally produced larvae collected from the Sturgeon River. The family group had unequal paternal representation (χ2=50.05; p = 4.7x10-9; df = 4) and decreased genetic diversity in contrast to the stocked naturally produced larvae that had high estimated number of breeders. Additional familial relationships were identified between the lake sturgeon produced via gamete collections and wild caught naturally produced larvae. These results evaluate the effectiveness of different stocking projects and methods across the Lake Superior basin to inform ongoing management plans and retain high levels of genetic diversity in stocked populations