Muscling their way back
By Callie Sacarelos, Communications and Marketing Coordinator
A consortium of researchers have been monitoring the Mississippi River at Hidden Falls Regional Park for nearly 15 years. But it wasn’t until the summer of 2021 that they finally found what they were looking for. Diving beneath the water’s murky surface in full scuba gear, they discovered several 2-year-old Higgins Eye mussels. After 22 years of collective efforts to reintroduce the endangered species to this designated essential habitat, they found proof that these mussels are finally reproducing naturally.
Restoring native mussel populations is a lengthy process that often takes decades before seeing progress. Mussels artfully trick certain fish species into hosting their larvae, which briefly attach to the fish until they are ready to detach into habitat only the fish can reach. So, the first step for researchers is to discover the host fish—each mussel species has a unique pairing—and find a healthy habitat where the fish exist.
It took researchers all across the country nearly 15 years to discover the Spectaclecase mussel’s host fish. They tested some unlikely hosts, including mudpuppies, lampreys, aquatic insects, and even other mussels, in addition to more than 100 fish species. By comparison, most host fish are discovered after testing 20-30 species. Finally, four years ago in a lab at the Minnesota DNR Center for Aquatic Mollusk Programs, mussel-propagation biologists found the answer: Mooneye fish. Unfortunately, this fish doesn’t occur north of the St. Croix Falls Dam anymore, and Spectaclecase mussels no longer exist south of Hudson, Wis.
Allie Holdhusen, a Mississippi National River and Recreation Area biologist, and Mark Hove, a biologist from the University of Minnesota, are working with others from Macalester College and the Wisconsin DNR to track existing populations of the endangered Spectaclecase. They are part of the Mussel Coordination Team (MCT), which works closely with the Upper Mississippi River Conservation Committee composed of government agencies, universities, and consulting firms. The Mussel Coordination Team includes the U.S. Army Corps of Engineers, Mississippi National River and Recreation Area, St. Croix National Scenic Riverway, U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Coast Guard, and the DNR from Minnesota, Wisconsin, Iowa, Illinois, and Missouri, as well as colleges and universities, and environmental consulting firms.
Currently, Allie, Mark and others from the MCT are using techniques similar to those used to restore Higgins Eye to hopefully restore Butterfly, Winged Mapleleaf, Salamander and Snuffbox mussels in the Mississippi or St. Croix rivers. The St. Croix, in comparison to the Mississippi, benefits from fewer dams, fewer alterations to the riverbed, less pollution, less sediment from urban development, and less farming chemical runoff. As a result, its fish communities are more diverse, making it an excellent habitat for mussels. The Mississippi National River and Recreation Area is also an important habitat for mussels. Water quality in this section of the river is healthier than further downstream. Also, Zebra mussels haven’t taken hold in the park like they have in other parts of the river.
“When I first heard about Zebra mussel destruction in the 1990s, I thought about switching careers because I didn’t want to spend my life conserving something that might die out like the dodo bird,” Mark said. “But as a young professional I was learning about all these rare mussel species and I wanted to help them. So I followed my heart, to make the world a better place [...] A lot of passionate people are involved in this. We need to remember that we’re connected to the river and what we do with our lives does make a difference.”