(English) Muskellunge population assessment in two northcentral lakes aided by angler participation

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A population assessment of muskellunge (Esox masquinongy) in two connected northcentral Minnesota lakes allowed evaluation of angler data when assessing various population metrics, including the residual effects of historical stocking efforts, as a non local strain had been introduced into the native population during the 1970s. In 2012, the Minnesota Department of Natural Resources sampled and marked muskellunge using trap nets during the pre-spawning and spawning periods and electrofishing during the post spawn period, while anglers collected data from fish caught during the 2012 open water season. Angler released all fish after collecting a scale for genetic analysis. Microsatellite DNA genotypes were used to differentiate individuals thus identifying recaptures and to estimate accuracy derived from the stocked strain. Anglers reported catching 16% of individuals marked by biologists. Of muskellunge reported by anglers, 78% were from the lake where they were initially captured while 22% were reported in the lake opposite their initial capture. Postspawn movements suggested that more individuals migrated from the lake characterized as having preferred spawning and nursery habitat to the lake characterized as having preferred summer habitat and prey. The age and length frequency distribution of fish captured by anglers and trap nets were similar, while electrofishing sampled younger and smaller fish, likely because it occurred postspawn when many adults had moved offshore. The best estimate of adult population size was produced by a model incorporating fish length as a covariate. Density was estimated at 0.70 adults per ha or 1.92 adults per littoral ha. Higher percentages of nonlocal ancestry were associated with smaller maximum size potential in von Bertalanffy growth models. Our study described key population characteristics for a muskellunge population while demonstrating that anglers could reliably collect several specific types of data that supplement data collected by management agencies.