The Ebb and Flow of Walleye and Sauger in Two Large Midwestern Rivers

Large rivers are among the most productive ecosystems on earth, and the most affected by humans. Multiple anthropogenic stressors have decreased the productivity and resilience of these ecosystems for centuries, negatively affecting fish populations. Dam construction and downstream flow regulation have fragmented over 65% of the world's large river ecosystems, and dredging, riverbank protection, and leveeing have resulted in systemic simplification. Once simplified, large rivers are also more susceptible to further stressors like species invasions and climate change. In this presentation, we combine multiple long-term data sets and look back nearly 150 years to examine the consequences that a legacy of anthropogenic stressors has had on walleye and sauger populations in the Illinois and Mississippi rivers. Stable isotope data provide insight into changes in walleye and sauger trophic status, while community monitoring data provide insight into changes in walleye and sauger relative abundance, and that of other influential species as well. We then suggest potential rehabilitation efforts that may increase large river resilience to impending system change, and thus benefit walleye and sauger populations.