Inverse Distance Weighting Enables Estimation of Lakewide Dissolved Oxygen with Minimal Sampling

Quantifying suitable fish habitat in large water bodies can be a major challenge for resource-limited fisheries managers. In this study the Inverse Distance Weighting (IDW) tool in the ESRI ArcMap Spatial Analyst toolset was used to estimate suitable winter habitat for a lacustrine population of Arctic grayling in Upper Red Rock Lake, Montana using limited sampling. In the winters of 2014 and 2015 dissolved oxygen (DO) was measured at 15 locations throughout the 800 ha lake from October to April every other week. These data were used to generate maps of estimated, available DO that displayed strong correlation to actual, measured values (r > .90). The accuracy of DO maps produced using IDW was a surprise and demonstrates that using IDW to estimate available habitat can be a useful tool for fisheries managers whose sampling intensity is limited.