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Parks in Partnership: United States Fish and Wildlife Service

October 30, 2024

By: Erin Parker, Interpretive Services Supervisor

Fatmucket. Elktoe. Slippershoe. Pink heelsplitter. Three-horned wartyback. Pimpleback. Rayed bean.

Do these names ring a bell? Probably not to most of us! They’re the common names of some of southeast Michigan’s freshwater mussels, those hard-shelled aquatic critters that many of us may only know as “clams” and their relatives. It turns out that these animals play many important roles in the ecology of our aquatic ecosystems…and Michigan is home to 43 species.

Smaller, nonindigenous mussels such as zebra and quagga even colonize the shells of native mussels.

Mussel ecology

Typically, when we hear about mussels in the news, it’s not great. In the Great Lakes, non-indigenous species like zebra and quagga mussels clog intake pipes, take up huge quantities of the plankton that forms the basis of our aquatic food chains, and even colonize and outcompete indigenous species of mussels. But a diversity of underwater organisms feed everything from fish to birds.

Recently, in partnership with the United States Fish and Wildlife Services (USFWS), more than 7,600 fatmucket mussels were reintroduced into the Clinton River at several sites- including at Stony Creek Metropark and Wolcott Mill Metropark.

According to Mandy Annis, Fish and Wildlife Biologist with the USFWS, “The benefits of restoring the mussel ecosystem into the Clinton River includes continued improvements in water quality by reducing E.coli and nutrients, increased invertebrates for increased fish populations, and stabilized streambeds.”

This project, expected to span four years, was funded by the Great Lakes Restoration Initiative and is being used to better understand how replacing the native mussels back into their habitats can impact the water and wildlife in those systems.

Scientists reintroduce fatmucket mussels to the Clinton River at Stony Creek Metropark.

Freshwater mussel declines

Freshwater mussels may not get the attention of bigger, more obvious animals, but they make up one of the most endangered groups of species on the planet. Sensitive to all types of water pollution including road salts, manure and fertilizer runoff, and human waste from sewer overflows during heavy precipitation events. Mussels can’t escape their stream-and-lakebed homes when conditions change or run away from aggressive non-indigenous threats like red swamp crayfish.

Mussels also have a unique relationship with fish. During their larval stage, tiny baby mussels called glochidia ride along in the gills of a specific fish species until they eventually are large enough to drop off and bury themselves into the sediments. Fatmucket mussels utilize bass (both small and large mouth) as their host fish, which makes the Clinton River a good fit as both species are abundant. If conditions in an ecosystem change, fish may be able to swim to new areas, but mussels are stuck in place without any hosts for their tiny glochidia.

Each two-year-old fatmucket mussel is tagged with a unique code and its placement is noted. A grid (visible in the background of the photo) is used to manage the placement of thousands of small mussels.

Science of mussel restoration

In order to track the health of the mussels and success of the project, each mussel is tagged with a unique code and its precise location is noted. Even the substrate of the stream where each mussel is place is noted- is it rocky or sandy?

Water quality parameters as well as checks on mussels will help scientists understand how “head starting” the population by growing them out for two years and then restoring them impacts the mussels and the overall water conditions.

While these new additions to the Clinton River will be hard at work below the surface, they’ll mostly be invisible to human visitors to the river. Ideally, their work will be noted in cleaner water, greater biodiversity, and reductions in streambank erosion. Future years will also include reintroduction of additional species, further increasing the benefits.

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