Spawning season distribution in sub-populations of Muskellunge in Georgian Bay

Abstract:

Loss of spawning and nursery habitat has been implicated as a major factor in the widespread decline of Muskellunge Esox masquinongy populations in N. America. Although there is limited evidence of spawning-site fidelity in the Great Lakes populations of Muskellunge, such behaviour could result in recruitment failure if individuals return each year to spawning sites that have become degraded. In this study, we compare the spawning behaviours of individuals across three Muskellunge sub-populations in Georgian Bay, Lake Huron to address the hypothesis that the use of specific spawning sites and spawning-site fidelity is independent of the suitability of that habitat for successful recruitment. The study regions in Southeastern, Northeastern, and Northern Georgian Bay have experienced different impacts from human development and sustained low water levels. We used radio telemetry to tag 49 adult Muskellunge and tracked them for up to three years (between 2012 and 2015). Sufficient multi-year data were only acquired for 18 individuals in the Southeastern region, but of those, 17 showed fidelity to at least one activity center over two or more years. We found that male Muskellunge occupied significantly smaller activity centers and shallower depths than females during the spawning season. The locations of adult Muskellunge during this study were found in close proximity to current and historic nursery sites identified in each region by other studies, supporting the close spatial linkage between spawning and nursery habitats. This is the first study that confirms spawning-site fidelity in Georgian Bay Muskellunge and supports the spatial association between spawning and nursery habitat. The repeat use of degraded habitat by spawning adults, as appears to be the case in Southeastern Georgian Bay, highlights the need to identify and protect spawning and nursery habitat.