Responses of Native Freshwater Mussels to Remedial Dredging in the upper Hudson River

The Hudson River, New York, was contaminated with polychlorinated biphenyls (PCBs) from two General Electric plants over a period of ~30 years and PCBs are still present in sediment and biota today. The river provides habitat for a variety of plants and animals, including native freshwater mussels. Although little is known about mussels in this river, managers were concerned that a 7-year remediation program to remove PCB-contaminated sediments could affect mussels. From 2013-2019, we conducted stratified (non-remediated, before remediation, after remediation) quantitative surveys across 17-pool-stratum combinations across nine pools. Sampling was done during August through October of each year. At each site, divers excavated sediment from two 0.063 square meter quadrats on the riverbed. Divers excavated substrates to a depth of about 15 centimeters and placed material from both quadrats into a 6-millimeter mesh bag. Mussels were sorted from the sediments, identified to species, aged by counting external annuli, and measured for shell length. These data were used to generate estimates of species composition, density, size, structure, and ecosystem services of mussel assemblages pre- and post-remediation.