Speaker: Holly Embke
Basses and sunfishes are warm-adapted fishes that have increased in recent decades in Wisconsin. Concurrently, declines in cool-adapted species, including Walleye (Sander vitreus), have occurred but the cause is not understood. Multiple factors have been associated with these declines, including rising lake temperatures, habitat degradation, harvest, and species interactions. To quantify the role that competition and/or predation plays between increasing bass and sunfishes and the rest of the fish community, we are conducting a whole-lake experiment to remove bass and sunfishes from an experimental lake in northern Wisconsin while measuring the response of other fishes and invertebrates. In 2018, 2019, and 2020, ~220,000 fishes were removed, while species-specific fish catch-per-unit-effort (CPUE) and invertebrate relative abundances were measured. Golden Shiner and Yellow Perch CPUE increased. Overall, zooplankton have declined, while some groups of zoobenthos have significantly increased, indicating fish removals have altered the lake energy flow. We will continue removing fish in 2021 and monitoring these populations. This information will be used to understand the conditions necessary to support self-sustaining fish populations given global environmental change.