Evaluating the Effect of Dam Removals on Yellow‐Phase American Eel Abundance in a Northeastern U.S. Watershed

Abstract

AbstractThe negative effects of dams and the benefits of dam removal for anadromous fish populations have been well documented. Effects of dams on catadromous Anguillidae species may be less drastic, although documentation of the response of catadromous fishes to dam removal is limited. We developed a mark–recapture study design to estimate the abundance of catadromous American Eel Anguilla rostrata within a small coastal watershed and compare abundance estimates before and after barrier removal. In the Mill River, Taunton, Massachusetts, four dams have or will be modified for passage or removed. Mark–recapture sampling and modeling methods were developed and applied in Lake Sabbatia, the source of the Mill River, over 4 years from the initiation of restoration. Rectangular eel traps had higher CPUE than double‐funnel traps used in previous studies, and a tag retention study found high retention rates by using established methods (94% overall). Abundances of yellow‐phase American Eels have increased with improved passage and recruitment to sampling gear during the study period. Dam removal could have substantial benefits to the coastwide stock of American Eels, and methods to evaluate changes in abundances are important for resource management as well as restoration ecology and project selection.