AUTHORS: Matthew R. Acre, U.S. Geological Survey, Columbia Environmental Research Center; James J. Roberts, U.S. Geological Survey, Lake Erie Biological Station; Dustin W. Broaddus, U.S. Geological Survey, Columbia Environmental Research Center; Ryan J. Trimbath, U.S. National Parks Service, Cuyahoga Valley National Park; Curt P. Wagner, Ohio Department of Natural Resources, Division of Wildlife; Ramsey A. S. Langford, Summit Metro Parks; Eric Waits, U.S. Environmental Protection Agency, Office of Research and Development; Daniel J. Sullivan, U.S. Environmental Protection Agency, Office of Research and Development; Marc A. Mills, U.S. Environmental Protection Agency, Office of Research and Development; Nick Barkowski, U.S. Army Corps of Engineers; David M. Walters, U.S. Geological Survey, Columbia Environmental Research Center
ABSTRACT: Fragmented aquatic systems are ubiquitous across the globe. Dams and other water control structures represent significant barriers to fish passage. In many countries, these structures represent ageing infrastructure which no longer serve their original function prompting an accelerated dam removal period. In the U.S., nearly 1200 dams have been removed in the last two decades. Dam removals serve multiple functions such as securing public safety by removing failing infrastructure, defragmenting riverscapes, and restoring the natural aesthetics of the river. Additionally, removals offer an opportunity to inform conservation science and community recovery in reconnected systems. The Cuyahoga River, infamous for catching fire and one of the driving forces that established the Environmental Protection Agency, has undergone several dam removals since 2006. One of the last remaining dams, constructed in 1913, is slated to be fully removed by 2026. To empirically assess fish community response to current and future restoration efforts we established 12 sites on the Cuyahoga River. We electrofished each site four times annually from 2022 to 2024 following methods of the Ohio Environmental Protection Agency (OEPA). OEPA data was consistently collected on a 5- to 7-year cycle throughout the river and enabled us to directly compare historical assemblages (1987-2017) to more contemporary periods (2022-present). At the time of writing, we have collected over 20,000 fish and representing 60 species. We used ordination analyses, Bray-Curtis distances, and trajectory analyses to link disturbance events with community changes. The best predictor of community changes were dam removals followed by environmental variables such as river discharge. Other community metrics (diversity and richness) and trajectory analysis suggests communities downstream of the Gorge Dam, and with direct access to Lake Erie, are in a dynamic state. These baseline community data are critical to evaluate effectiveness of small and large restoration projects such as dam removals.
