New York State Department of Environmental Conservation (DEC) has announced that an innovative project that is relocating freshwater mussels in the Grasse River during an ongoing river remediation project is showing early signs of success and reporting a 98 percent survival rate.

As part of an U.S. Environmental Protection Agency (EPA)-led cleanup project to remove polychlorinated biphenyls (PCBs) from river sediments, a seven-mile stretch of the lower Grasse River in northern New York in being dredged and capped starting next year. Before dredging begins, DEC is collecting mussels from the river bottom and temporarily placing them in areas that won’t be subject to capping or dredging. The New York State Museum, St. Regis Mohawk Tribe, and SUNY Cobleskill are collaborating with DEC on the project.

Divers are currently working in the Grasse River, collecting mussels and relocating them out of harm’s way. DEC is relocating 4,700 mussels this year in addition to the more than 4,000 mussels moved in 2017, and approximately 2,000 mussels were safely placed in cages in other parts of the river. Approximately 98 percent of these relocated mussels survived the winter, proving the applicability of this previously untried technique. Mussels that were not caged were placed back into locations in the river where remediation efforts will not affect these bivalves.

Surveys of the Grasse River have shown that 10 different mussel species are found in the river, four of which are listed as Species of Greatest Conservation Need. Mussels are important for the healthy functioning of freshwater ecosystems and can make up a majority of the biomass within an ecosystem. Results of this work have demonstrated that the Grasse River has a dense and robust mussel population.

In addition, a healthy mussel population directly benefits the water quality of the area. As filter feeders, mussels obtain their food by filtering out microscopic organisms, mostly microalgae, from the water column. Mussel restoration offers the potential, as water quality improves, to provide a more stable environment for additional mussel growth.

Because the geographic scope of the remedial project is so vast, EPA estimates that up to 1.4 million mussels will be killed during the dredging and capping. Natural recolonization of the remediated river sediments by mussels would take decades without help. This initial effort is to provide small founder colonies to jump-start future recovery.

The relocation project is supported by Return a Gift to Wildlife, a state program funded by voluntary donations New Yorkers consider on their tax returns.

Photo of east elliptio mussel courtesy DEC.