General Electric Company (GE) directly and indirectly released polychlorinated biphenyls (PCBs) into the Hudson River and the surrounding environment starting in the late 1940’s, making it one of the most PCB-contaminated rivers in North America. Source control at two GE plant sites was implemented in 2009 to stem the influx of PCBs into the river (NYSDEC 2004; Farrar 2013; NYSDEC 2015). The Hudson River, like many other rivers, contains populations of native freshwater mussels—a group of animals that perform vital functions in freshwater systems. While there was anecdotal evidence of mussels residing in the Upper Hudson River (north of Troy, NY; GE 2005, GE 2009), quantitative data on mussel assemblages was lacking. Systematic, quantitative surveys for native mussels were completed in 2013 and 2015 in a total of six pools of the Upper Hudson River including one reference pool (Feeder Dam) located upstream of the former GE plant sites and five contaminated pools downstream of the GE plant sites (Thompson Island, Fort Miller, Northumberland, Stillwater, and Upper Mechanicville). Surveys were designed to estimate species composition, relative abundance, population size, population structure, and ecological services (i.e., biomass and filtration) of mussel communities prior to and after remedial actions to remove PCB contaminated sediments (i.e., dredged and subsequently capped or backfilled). In most pools, the experimental design incorporated stratification on remediated (before or after remedial activities were completed) and non-remediated areas. ... (access to the full abstract is restricted)