Passage Evaluation and Costs-Benefits of Nature-like Fishways: New England Case Studies

While NOAA and other federal resource agencies target full removal of dams and other barriers as the preferred alternative to restoring free-flowing rivers and riverine ecological functions, a multitude of site, socio-economic and technical challenges often restrict or prevent complete barrier removal. Nature-like fishways are installed to maintaining existing or establishing new grade controls with an overarching goal of efficient and safe fish passage, but a trade-off of limited or no discrete benefits to other ecological functions such as sediment transport and floodplain restoration. This analysis covers eight case studies of full-river width and bypass channel nature-like fishways completed with funding and technical assistance contributed by NOAA, targeting anadromous fish passage. We present an evaluation of the fish-run flow hydraulics and fishway dimensional features using a diagnostic field protocol, and comparing site conditions to federal interagency passage criteria for Atlantic Coast diadromous fishes. Target species passage performance is discussed, and other project outcomes, including ecological changes, social values and project costs, are also summarized.