Effects Of Dams On Community Assemblages Prior To Removal In a High Quality River System In Vermilion County, Illinois
Dams change rivers from lotic to lentic habitats, there by affecting sediment transportation, habitat connectivity and water quality. These changes in the environment disrupt fish dispersal leading to changes of fish assemblages over time. The Vermilion River located in East-Central Illinois has several impoundments. Two particular impoundments in the system are the Danville Dam located 22 miles upstream of the Wabash River on the main channel and the other located on the North Fork tributary upstream of Danville dam. We sampled 12 sites (six site associated with each dam) using DC electrofishing during October 2012. Over all sites sampled we collected 54 different species. The North Fork tributary was dominated by Centrarchidae making up 59.2% of the assemblage. Cyprinidae was the most abundant family found in the Vermilion River sites consisting of 65.5% of the total catch. Non-metric multi-dimensional scaling (NMDS) suggested fish communities below Danville dam to be similar to communities found above extent of the pool. The results from NMDS also showed dissimilarities between the pool community and the upstream river community on the smaller North Fork. Overall clustering in the NMDS suggested the river communities from the North Fork were different than the Vermilion River. Though similar species were collected throughout the system, several species such as the bigeye chub, brindled madtom, largemouth bass, multiple redhorse species and sauger had restricted distributions. This study will serve as a baseline model to test the efficacy of dam removal in restoring the diversity and structure of river communities.