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Uncovering Mussels in the Rivers and Creeks of the Chicago Area

This story was written by Lucas Chamberlain, science communications fellow at Shedd Aquarium.

Everyone loves an underdog; and perhaps no creatures deserve a conservation comeback more than the remarkable mollusks cleaning our streams and rivers—freshwater mussels.

With unusual names like pocketbook, pigtoe and pimpleback to rabbitsfoot, fatmucket and snuffbox, these incredibly diverse animals (over 300 species in North America alone!) are nature’s water filtration system. By removing harmful algae and bacteria from our water, as well as protecting streambeds from erosion, the mussels of the Great Lakes region are “the livers of the rivers” and a foundational keystone animal.

Two hands holding various large mussels above a river

For thousands of years, people in the Great Lakes region have also depended on mussels for cultural and economic value. Native American cultures prized the bivalves for food, toolmaking and jewelry. European settlers coveted their pearly shells for button-making and nearly over-harvested the animals to extinction. Today, parts of freshwater mussels are implanted into oysters for quick pearl development and remain essential components of a global pearl industry.

Anchored into streambeds with a muscular “foot,” freshwater mussels can live for decades (or longer!). However, mussels are highly sensitive to disturbances such as habitat degradation, invasive species and industrial pollution. For these reasons, freshwater mussels are considered “water quality indicators,” which scientists use to measure the health of our waterways.

In order to optimize conservation and management strategies that seek to preserve precious and imperiled freshwater mussels, Shedd Aquarium has partnered with agencies such as the Forest Preserves of Cook County and DeKalb County to learn more about the freshwater mussels in the Great Lakes region—with a focus in the Chicago area—and the challenges they face. Shedd Research Biologist Kentaro Inoue, Ph.D., has been working diligently to survey mussel populations, map their distribution and uncover the genetic diversity hidden just beneath the streambed.

Researcher Kentaro Inoue stands chest-deep in a river holding a large mussel

This summer, Inoue and a dedicated team of citizen scientists, waded into the Kishwaukee River, Nippersink Creek and Poplar Creek to continue long-term monitoring of mussel communities in these waterways. Once there, Inoue and his team found, measured and PIT tagged—like the implants you would use on your cat or dog—all mussels in a certain area before taking genetic samples.

At first glance, this research looks a lot like desperately searching the ground for something you accidentally dropped—the back of an earring, a thumb tack, etc.—but this group of about ten is donning wetsuits, waders and swimwear.

After roping off a 150-square-meter transect of the creek or river, the field team forms into a line at one end of the transect, crouches down on their hands and knees, and begins to carefully comb through the sandy gravel. Inching upstream as clouds of sediment form in the water column, the team cheers as they come across unsuspecting mussels and places them in mesh collection bags until they can be measured, tagged and placed back into the streambed.

At some research sites, the water is clear enough to see mussels nestled in the substrate with your naked eye. At others, you’re reliant on your sense of touch. Is it a rock? A crayfish or snapping turtle? Blindly surveying the sand, gravel and mud is not for the faint of heart! If mussels had been tagged during a previous day of research, though, a waterproof PIT tag reader can be used, which beeps in the same way a metal detector would on a sandy beach.

Researchers sit on a river bank, measuring mussels

The goal is to find as many mussels as possible. Combined with Shedd’s first year of mussel research that took place in 2020, the least mussels have been detected in the swift muddy waters of Nippersink Creek, which produced 171 individuals from 10 species. In juxtaposition, a tranquil Kishwaukee River provided ideal conditions to find 521 mussels from 12 species. Finally, bracing themselves for frigid currents, Inoue and his team uncovered 198 individuals from five species at Poplar Creek over two years.

Most of the mussel species they have found are common, but Inoue was overjoyed to discover a single Black Sandshell at Nippersink Creek, which is a species of concern of Illinois. The team also uncovered other species of concern including the Ellipse, Flutedshell and Elktoe.

By returning year after year, Inoue hopes to better understand how imperiled mussel populations change over time and what factors threaten their survival. Information gathered about how best to protect mussels can help inform management strategies or environmental policies.