The fragmentation of river habitats through dams and poorly designed culverts is one of the primary threats to aquatic species in the United States (Collier et al, 1997; Graf, 1999). The impact of fragmentation on aquatic species generally involves loss of access to quality habitat for one or more life stages of a species. For example, dams and impassable culverts limit the ability of anadromous fish species to reach preferred freshwater spawning habitats from the sea and prevent brook trout populations from reaching thermal refuges. The Northeastern U.S. (the New England and Mid‐Atlantic states) has the highest density of dams and road crossings in the country, with an average of 7 dams and 106 road‐stream crossings per 100 miles of river (Anderson and Olivero Sheldon 2011).
Throughout the Northeast, hundreds of dams have been removed and hundreds of culverts have been replaced or retrofitted over the last two decades in projects where ecological restoration was a goal. To many working in the field of aquatic resource management it is apparent that given likely future constraints on availability of funds and staffing, it will be critical to be more strategic about investments in connectivity restoration projects. One approach to strategic investment is to assess the likely ecological “return on investment” associated with connectivity restoration. In order to complete an assessment at the regional scale, the Northeast Association of Fish and Wildlife Agencies (NEAFWA) awarded the Nature Conservancy (TNC) a 2007 Regional Conservation Needs (RCN) Grant. This RCN grant was designed to have TNC support state resource agencies in the Northeast U.S. (fish and wildlife, marine fisheries, dam safety, etc.) in efforts to strategically reconnect fragmented river, stream, coastal, reservoir, lake and estuarine habitat by removing or bypassing key barriers to fish passage. The primary ecological goal of mitigating fish passage barriers is to enhance populations of fish including anadromous fish, coldwater species, and other species of greatest conservation need (SGCN).