Assessment of the Effects of Habitat, Harvest and Community Interactions on the Abundance of Walleye Sander Vitreus in Inland Lakes Throughout Ontario
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Walleye (Sander vitreus) is an important species to the recreational fishery throughout Ontario. Fish community interactions between walleye and other species are rarely considered when establishing management targets which may lead to the creation of conflicting management objectives. Other studies that have focused on competitive interactions between species have typically focused on interactions between two species in isolation of the remaining species within the fish community and considered only a small subset of lakes. My study examined how the presence/absence of multiple species within the fish community affects the abundance of walleye across a broad spectrum of habitat conditions and fisheries. A Schaefer model was modified by distinguishing carrying capacity into a habitat and fish community component to account for between lake differences in suitable habitat prior to testing for interactions. Walleye catch-per-unit effort (CUEW, kg/net) was assessed in 140 Ontario lakes using the Fall Walleye Index Netting Protocol. An all subsets approach was used to estimate parameters in a multiple regression. Fish community and fishing pressure were significant predictors in explaining walleye abundance (adjusted R2=0.45, p<0.001). The presence of bluegill (Lepomis macrochirus) and smallmouth bass (Micropterus dolomeiu) were significant negative predictors in the top model (αbluegill = -1.54, partial r2=0.1; αsmallmouth = -0.28, partial r2=0.03). In many studies, smallmouth bass have also been found to have a significant diet overlap with walleye. These interactions present challenges when establishing management objectives for mixed fisheries.