Quantifying Isotopic Niche Overlap: The Effect of Water Clarity On Dietary Resource Partitioning Between Walleye and Smallmouth Bass In Boreal Shield Lakes

It is unclear how climate-induced water clarity shifts will affect interactions between native dark-adapted walleye and invading smallmouth bass in northern Ontario. This study used stable isotopes of nitrogen (¹⁵N) and carbon (¹³C) in fish muscle tissue to investigate how water clarity affects the partitioning of resources drawn from the base of the food web between walleye and smallmouth bass collected from 34 small (100-200 ha) Boreal Shield lakes. Quantitative metrics of isotopic interaction (area of overlap between multivariate ellipses in δ¹⁵N vs. δ¹³C biplot space, and distance between population centroids) were not significantly correlated with Secchi depth (m), DOC (mg/L), or true colour (TCU). Moreover, water clarity indices did not explain a significant proportion of the variation in any measure of isotopic niche dimensions for either species (area of ellipse, lengths of ellipse axes, or eccentricity). These results suggest that water clarity is neither a main driver of isotopic interaction between these species nor a main driver of dietary shifts. An analysis investigating other potential community and habitat predictors of isotopic interaction will also be presented. This research will shed light on which habitat characteristics impact walleye resilience in the face of invading smallmouth bass.