Index of nursery habitat suitability for muskellunge in Georgian Bay, Lake Huron.

Abstract

To support Georgian Bay’s self-sustaining Muskellunge Esox m quinongy fisheries, we developed two index of nursery habitat suitability (INHS) models that can be used to identify and monitor the quality of Muskellunge nursery habitats in coastal wetlands. The INHS models were based on habitat features found in wetlands with age-0 Muskellunge identified at two large embayments in northern Georgian Bay. One INHS model had five variables that included proportional abundance of Yellow Perch Perca flavescens, proportional abundance of cyprinids, fish species richness, the wetland’s substrate slope, and a metric related to macrophyte abundance. The other INHS model included only three variables from the five-variable INHS, omitting information on macrophyte and fish species richness. When they were applied to an independent data set, both INHS models successfully tracked deterioration in nursery suitability after 15 years of sustained low water levels in Georgian Bay, but the five-variable INHS had higher overall accuracy and showed stronger discrimination between sites with and without young of the year. We applied the three-variable model to classify coastal wetlands in other regions of Georgian Bay and obtained a false-negative rate less than 13%. We also obtained a higher false-positive rate with the three-variable model compared with the five-variable model (54% versus 31%) because it required a lower threshold to indicate suitability (0.6 versus 0.70, respectively). These INHS models should allow managers to screen for suitable nursery habitat near current spawning sites across Georgian Bay and allow managers to predict how changes in water-level regimes might affect the suitability of spatially explicit wetland units.