This summer, U.S. Army Corps of Engineers Louisville District employees, along with other state and federal agencies, completed mussel salvage efforts along approximately 14 river miles on the Green River in Kentucky.
“The Green River is a unique ecological resource for the state of Kentucky,” said Louisville District Wildlife Biologist, Jeff Hawkins. “The river has more than 150 fish species and 70 species of mussels, including 43 species existing nowhere else in the world.”
Due to the recent removals of aging infrastructure no longer needed for commercial navigation, such as Green River Lock and Dam No. 5 and Green River Lock and Dam No. 6, USACE completed an environmental impact analysis as a requirement of the National Environmental Policy Act to assess the impact the removals would have on the human and natural environment.
“Although freshwater mussels have some ability to maneuver short distances, they mostly stay put their entire lives,” said Zac Wolf, limnologist for the Louisville District Water Resources Section of the Engineering Division Hydraulics and Hydrology Branch. “They can easily get blocked by obstacles, such as logs or rocky shores, and get stranded and die.”
Freshwater mussels are one of the most imperiled groups of animals in North America. They are critical components to Kentucky’s aquatic ecosystems and many are unique or endemic to specific streams or watersheds. Some species of mussels are indicators of good water quality and overall health of an ecosystem; they have complex life cycles that require host fish or amphibian species to complete their lifecycles. Many of these host species are also threatened by habitat loss or alteration and pollution. In addition, freshwater mussels are filter-feeders that effectively “clean-up” rivers by filtering out particles and chemicals in the water, according to the team.
The removal of aged infrastructure on the Green River and Barren River collectively makes it one of the largest stream restoration projects in the country, reconnecting dozens of river miles without manmade barriers. “These changes will improve passage for aquatic organisms and restore instream habitat for riverine fish, mussels and other invertebrates,” Hawkins said.
Wolf noted that the salvage efforts will have a significant impact on the local ecosystem for decades to come. “Our efforts to salvage mussels gives the ecosystem a leg-up when it comes to recovery,” he said. “It’s a really unique opportunity to save the environment in a direct way.”
The 2024 mussel recovery effort resulted in the salvage of more than 13,000 mussels, including a few rare species which provided critical information for conservation efforts.
Organizing a large-scale, multi-agency effort over four days with more than 35 volunteers created the largest challenge for the team. Weather and on-site conditions, including water levels, determined when teams could act. In addition, participants needed to use canoes and kayaks to closely inspect the riverbank.
To accomplish the task, despite these challenges, the team placed a strong emphasis on communication and planning and the river was broken up into sections so that teams could spread out to cover larger areas in less time.
This concerted effort involved coordination across multiple federal and state agencies, including USACE, U.S. Fish and Wildlife Service, National Park Service, The Nature Conservancy, Kentucky Department of Fish and Wildlife, Kentucky Division of Water and the Office of Kentucky Nature Preserves.
“Freshwater mussels appear to be boring, but if you just do a little bit of reading into them, you find they are surprisingly charismatic and dynamic animals that have adapted to survive in very “creative” ways,” Wolf said. “Because the Louisville District is situated in a global hotspot for freshwater mussel diversity, they certainly deserve our attention.”