RAPID: Contrasting Ecological Gradients Before and After Dam Removal

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Thousands of small mill dams were constructed in the Great Lakes region during the 1800's. The ecological communities above and below these dams become quite different. Public safety concerns now require removal of many dams and open a migration corridor that can change ecological interactions. This project focuses on a recent dam and reservoir removal in Big Spring Creek near Briggsville, Wisconsin. The upstream community contains a typical cold water fish assemblage dominated by brook trout, sticklebacks, sculpins and creek chubs. The reach below the dam is dominated by a typical warm water assemblage--largemouth bass, bluegill, yellow perch and white suckers. Monitoring seasonal changes in water temperature, fish community structure and food web structure will test the alternative outcomes posed in two questions:1. Will the colder water displace the warm water fishes and allow the cold water assemblage to expand downstream?2. Will the dam removal allow upstream invasion by large predators (bass) and competitors (suckers) that can reduce and displace the coldwater fish community?More that 400 small dams are scheduled for removal in Wisconsin during the current decade. Public interest in outcomes is always high. Results of this study will offer guidance and expectation of the ecological changes that result from similar dam removals. This project will provide support to a graduate student plus four undergraduate hourly employees. It will also serve as a demonstration site for the Ecology of Fishes class (48 students) at UW-Madison.