Dam Removal Benefits American Eel Restoration at Landscape-Scale

Migration barriers are recognized as a contributing cause to declining American Eel (Anguilla rostrata) populations in the eastern US. We used time-series analysis to evaluate the effects of a dam removal on American Eel abundance in headwater streams approximately 150 km upstream from the former dam site (Embrey Dam, Rappahannock River, Virginia). Observed Eel abundances after dam removal exceeded predictions from time-series models parameterized with data prior to dam removal. Mann-Kendall analyses also revealed consistent increases in Eel abundance after dam-removal but inconsistent temporal trends before dam-removal. Increasing Eel numbers could not be attributed to changes in local physical habitat (i.e., mean stream depth or substrate size) or regional population dynamics (i.e., abundances in Maryland streams or Virginia estuaries). Results indicated that the dam previously impeded migration of many small-bodied individuals (i.e., < 300 mm TL). We hypothesize that restoring connectivity to headwater streams could increase population growth rates by increasing female Eel numbers and fecundity.