Forecasting the effects of invasive dreissenid mussels on walleye (Sander vitreus) habitat occupancy and yield

Abstract

Over the past few decades, dreissenid mussels have been introduced in North America and have caused changes in various ecosystem responses including water clarity and fish production. This thesis investigates the response of walleye populations to dreissenid invasion. A predictive model was developed to estimate increases in water clarity following dreissenid mussel invasion and extended to predict an increase in mixing depth and decrease in walleye yield from an Ontarian dataset. Observed declines in walleye yield where dreissenids have invaded were determined to be partly due to increases in water clarity, but concurrent declines in total phosphorus and angler effort likely contributed as well. Finally, walleye production models were developed for Manitoban Boreal Shield and Plains lakes, highlighting the importance of total phosphorus as an indicator of primary productivity in Plains lakes. These walleye production models were related to the water clarity model and small changes in walleye yield post-dreissenid invasion were predicted. These predictive models could prove to be useful tools to managers in uninvaded lake ecosystems.