Walleye (Sander vitreus) are an important fish for the Ojibwe (Anishinaabe) people. Since a recorded high in the early 2000’s the population of Walleye (Sander vitreus) have been steadily decreasing while populations of largemouth bass (Micropterus salmoides) have been increasing. Different factors were identified and tested at Fish Lake Reservoir north of Duluth, MN and they include: temperature, predation, dissolved oxygen (DO), and vegetation. Experiments were carried out using a Hydrolab probe that took data at depths a foot apart until the bottom was reached. Preliminary conclusions include surface water being too hot to sustain Walleye (Sander vitreus), deeper waters have too low of DO levels that stresses the fish, and vegetation spreads which then dies, decomposes and uses oxygen; as of now, Walleye (Sander vitreus) are limited to where they can live at Fish Lake Reservoir.