Unique Georgian Bay nursery habitat features allows for successful habitat differentiation: Steps towards a spatially explicit muskellunge nursery habitat suitability index model

In Ontario, muskellunge (Esox masquinongy) management strategies are predicated on self-sustaining populations to ensure high quality trophy fisheries. These strategies provide safeguards for breeding adults and their spawning habitats. In Georgian Bay, Lake Huron, suitable spawning habitat appears pervasive given the Bay’s oligotrophic status. However, after more than a decade of sustained low water levels and increases in shoreline modification, coastal wetland nursery habitat structure has been altered for which muskellunge young-of-the-year (YOY) are sensitive. Thus, despite the presence of suitable spawning habitat, muskellunge populations may fail is suitable nursery habitat is limited or absent. This hypothesis was supported in southeastern Georgian Bay where suitable muskellunge spawning habitat failed to support YOY from a lack of suitable nursery habitat structure and altered fish community. Unfortunately, very little information exists that can help managers identify suitable nursery habitat in Georgian Bay which may be more limiting to recruitment and spawning habitat. To address this knowledge gap, a region in northern Georgian Bay was sampled for YOY muskellunge during 2012-13 to describe and quantify habitat parameters related to muskellunge nursery habitat in the absence of shoreline modification. Multivariate statistical techniques successfully differentiated muskellunge nursery sites from available habitat. Results suggested that suitable muskellunge nursery habitat in Georgian Bay encompassed a relatively narrow range of habitat parameters characterized by: steeper substrate slopes, greater densities and diversity of upper water column structuring submerged aquatic vegetation (SAV) and relatively low densities of low growing SAV. Muskellunge nursery habitat characteristics also p4romote a more diverse fish community and limited abundances of yellow perch (Perca flavescens) than sites absent of YOY muskellunge. These results are forming the basis of a spatially explicit muskellunge nursery Habitat Suitability Index (HIS) model for Georgian Bay. This HIS can nbe used in conjunction with current management strategies to provide a more holistic, complementary approach to managing muskellunge populations by accounting for the life stage habitats limiting to recruitment.