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Surveying Freshwater Mussels

While they spend most of their lives half-buried in the muddy bottoms of lakes and streams, native free-living freshwater mussels are vitally important to the health of their aquatic ecosystems. Due to habitat loss and water pollution, however, freshwater mussels are also one of the most endangered groups of animals in North America. Shedd Aquarium is conducting surveys in the Great Lakes region to determine which species are found where and how genetically diverse different populations are. Pairing these data with long-term studies of individual animal survival will inform habitat restoration and conservation management strategies.

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Two hands holding various large mussels above a river

Mussels’ complex life cycle

Mussel larvae parasitize freshwater fishes, but not just any fishes: Different mussel species have specific fish hosts. Female mussels often lure their desired host fish to them, then release their larvae, which attach to the fish’s gills or fins. For weeks, or even months, the developing larvae hitch a ride until they reach a certain size and detach. The now-juvenile mussels settle into an area and burrow into the mud bottom, growing into relatively stationary adults. Research biologist Kentaro Inoue is studying these animals through genetic analyses to understand the connectivity and genetic diversity of species’ populations.

“Freshwater mussels are the ‘livers’ of rivers and lakes. They filter water and remove bacteria and contaminants to support healthy freshwater ecosystems, including the sources of our drinking water.”

Kentaro Inoue, research biologist
Two adults in wetsuits stand shoulder-deep in a green river
Researchers sit on a river bank, measuring mussels

Conservation teamwork

Surveying freshwater mussel populations is slow, wet work. Wearing masks, snorkels and sometimes even wetsuits, Shedd biologists, staff members and volunteers span the width of a river or stream and, acting like racoons, paw the substrate until they find an animal (or sometimes a rock). After collecting mussels in mesh bags, individuals are identified by species, measured and aged by counting the growth rings on the shell. Then the mussels are returned to the river. Shedd is working with a variety of partners, including the Illinois Natural History Survey, DeKalb County Forest Preserve District and Openlands, to gain a holistic understanding of species, habitat and threats and then develop conservation management and species recovery strategies.