Genetic and phenotypic evidence for splake presence in brook trout and lake trout spawning habitats

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© 2016 International Association for Great Lakes Research. Management of Michigan's fisheries relies extensively on hatchery fish. Hatchery production in Michigan includes splake, a fertile hybrid produced artificially by crossing lake trout (Salvelinus namaycush) and brook trout (Salvelinus fontinalis) that are stocked in near-shore waters of the Great Lakes. Splake seldom occur naturally because brook trout and lake trout are typically reproductively isolated in space and time. Because some splake are fertile, concerns have been raised over splake stocking based on observations of fish of intermediate phenotype in brook trout and lake trout spawning areas. The overall goal of this project was to determine whether splake are present on brook trout and lake trout spawning habitats. We analyzed 10 microsatellite loci to genotype putative splake collected from two brook trout spawning tributaries to Lake Superior, known hatchery splake, and Michigan Department of Natural Resources (DNR) lake trout and brook trout hatchery strains used in the splake program. Identification of fish of intermediate phenotype as F1 hybrids or either parental species in the two brook trout streams was based on species-specific genotypic differences resolved using Bayesian model-based clustering. Four hybrids were identified among the 15 putative splake from the two brook trout streams. Collections were made at several lake trout spawning reefs to quantify the number and reproductive status of splake, revealing that approximately 56% of captured splake were sexually mature. Results from spawning areas of both parental species confirm that splake were present and may pose a threat to the genetic integrity of spawning populations where they occur.

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Journal of Great Lakes Research