AUTHORS: Alexander Searfoss, Central Michigan University; Kevin Pangle, Central Michigan University; Jerry Sweeten, EcoSystems Connections Institute; Scott Mcnaught, Central Michigan University
ABSTRACT: In November 2021, the low-head dam in Logansport, Indiana, was removed, reconnecting the Eel River to the Wabash River and the Gulf of Mexico for the first time in over 200 years. The goal of this study was to evaluate changes in fish community structure and function and document the upstream recolonization of the Eel River following dam removal. Sampling was conducted annually from 2022 to 2024 at 10 sites along the river, spanning from river mile 1.1 to 74.9, using a combination of electrofishing, seine nets, and environmental DNA (eDNA) methods. The eDNA analysis targeted three native species—Common Logperch (Percina caprodes), Bluebreast Darter (Etheostoma camurum), and Tippecanoe Darter (Etheostoma tippecanoe)—and three invasive species—Bighead Carp (Hypophthalmichthys nobilis), Silver Carp (Hypophthalmichthys molitrix), and Grass Carp (Ctenopharyngodon idella). Post-removal fish community data were compared to pre-removal records from the Eel River and the Mississinewa River, a nearby watershed that remains disconnected from the Wabash River. Since the dam removal, 14 new species have been documented in the Eel River, including 12 native and 2 invasive species, resulting in a 14% increase in species richness. In contrast, the Mississinewa River experienced a 14.6% decline in species richness over the same period. Newly detected species were observed as far upstream as river mile 36, with the most significant changes occurring between river miles 1 and 10. Although species diversity has increased, further monitoring is required to understand the long-term impacts on fish community dynamics. The removal of low-head dams offers a valuable restoration tool for improving riverine fish community structure and ecosystem function.
