Potential Ecological Implications of Providing American Eel Passage in the Susquehanna River Watershed

American eel (Anguilla rostrata) occupies a unique niche in estuarine and freshwater habitats along the Atlantic coast but have experienced a range-wide population decline during recent decades. The Chesapeake Bay watershed supports a large portion of the eel population, but a large geographic area is inaccessible due to dams on the lower part of the Susquehanna River. In 2008, USFWS began stocking eels above dams to evaluate the reintroduction of eels. Laboratory studies conducted by the USGS indicate that eels are a good host for the common freshwater mussel, eastern elliptio (Elliptio complanata) in the Susquehanna River. Low abundance and lack of recruitment of eastern elliptio in the Susquehanna River, in comparison to nearby watersheds, could be related to the lack of eel passage in the Susquehanna River. Following targeted eel stocking in tributaries to the Susquehanna River, monitoring indicated increased eastern elliptio recruitment and wide distribution of stocked eels.  The presence of healthy freshwater mussel beds provides streambed stability, water filtration, and increased macroinvertebrate biodiversity.  Permanent eel passage resulting from FERC relicensing of hydropower facilities could lead to improved ecological function in the watershed.