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Purpose
RATIONALE: During the past decade, assessments have indicated the emergence of natural lake trout recruitment in most management units across Lake Huron based on collections of YOY and unmarked individuals. Because wild fish are unmarked, managers lack the ability to characterize temporal and spatial patterns of strain-specific recruitment and whether recruitment at specific locales can be attributed to: (1) reproduction of strains stocked at or near each sampling station, or (2) dispersal and immigration of individuals from strains stocked elsewhere (source-sink effect). Previous research by PLs Stott and Scribner has shown that strain abundance at spawning locales are poor predictors of strain-specific reproductive success, but this work predated the recent lake-wide emergence of natural lake trout reproduction and was not spatially extensive enough to address the general questions of dispersal and local stocking to lake-wide natural recruitment. Knowledge of recruitment levels of hatchery strains stocked in different management units and how strain-specific recruitment varies across years, locations, and as a function of local or regional stocking efforts will provide information needed to improve future stocking and management of the potential transition process from primarily hatchery stock to wild stock. Better understanding of how strain-specific recruitment contributed to the nascent recovery of wild lake trout over years and locations in Lake Huron would also aid restoration in other lakes.
OBJECTIVES: The main goal of our project is to determine the relative contributions of stocked lake trout strains to the fisheries and how strain contributions varied over years, age groups and geographic locations. Specific objectives are to: (1) simultaneously estimate year and strain composition for wild mixed samples across Lake Huron and determine how these contributions differ among years and across management units; (2) determine whether contributions of different hatchery strains to natural recruitment is related to differences in relative stocking proportions or to dispersal; (3) determine whether contributions of specific hatchery strains is consistent across locations.
