PRAIRIE DU SAC – Nearly 15 years after state and federal biologists first used bass and walleye to deliver endangered freshwater mussels to their new home on the Wisconsin River, biologists from the Wisconsin Department of Natural Resources and other state and federal agencies have returned to find good news.
The biologists’ diving surveys earlier this summer revealed the federally endangered Higgins’ eye mussels are surviving, growing and in good condition at the site. And, they have not succumbed to invasive zebra mussels once feared to threaten their existence.
Zebra mussels are regarded as the most severe threat to native mussels already suffering declines due to pollution, habitat loss, overharvest and other factors. Zebra mussels can outcompete native mussels for food and attach to their shells in such great numbers they essentially smother the natives.
“It’s great to know we can propagate and restore our native mussels and that we can overcome the impacts of zebra mussels at this site,” DNR Conservation Biologist Lisie Kitchel said.
Kitchel serves on the multi-state, multi-agency project to jump start Higgins’ eye populations. The project’s mussel work at Prairie du Sac in Sauk County and downstream in Richland County stems from a partnership involving several federal and state agencies, academics and citizens to assure a species once common and widespread in the Upper Mississippi River doesn’t vanish.
Freshwater mussels are an important part of aquatic ecosystems. The mussels help filter water to keep it clean, provide food for fish and wildlife, stabilize the riverbed and provide valuable habitat for many creatures that inhabit streams.
The partners decided to reintroduce Higgins’ eye mussels to 10 sites in Wisconsin, Minnesota, Iowa and Illinois with a goal of achieving self-sustaining populations in at least five of the sites. In Wisconsin, two sites on the Lower Wisconsin Riverway were selected, below the Prairie du Sac dam in Sauk County and in Richland County at the Orion Mussel Bed State Natural Area, recognized as one of 14 Essential Habitat Areas for Higgins’ eye.
Higgins’ eye mussels were propagated at the Genoa National Fish Hatchery and larval mussels, called glochidia, were placed in tanks with largemouth and smallmouth bass and walleye. In the wild, these fish species serve as hosts to mussels’ larval stage. Stocking trucks carrying the fish were backed up to the river and the fish were released into the water. The glochidia later dropped off the fish and settled into the river bed. In addition to the stocking, two- to three-year-old Higgins’ eye raised in cages in the Mississippi River and transported to the Wisconsin sites were hand-placed by divers onto the river bed.
Dan Kelner, a St. Paul-based U.S. Army Corps of Engineers biologist leading the mussel project, said the Corps started the Higgins’ eye effort in 2002 to meet federal Endangered Species Act requirements that the Corps’ Mississippi River navigation channel not jeopardize the Higgins’ Eye and other aquatic species.
“One of our main goals was to establish new and protect reproducing populations of Higgins’ eye outside of the main channel areas threatened by the zebra mussels,” Kelner said. “We feel we’re having success here on the Wisconsin (River).”
Data from summer 2016 surveys are still being compiled, but on the Wisconsin River site below the Prairie du Sac Dam, good numbers of Higgins’ eye delivered by hand and by fish have been found.
About one-half of the 51 mussel species in Wisconsin are threatened or endangered, and in North America as a whole, 70 percent of the 300-plus mussel species are extinct or imperiled, U.S. Fish & Wildlife Service says.
The project’s biologists say the mussel project has yielded benefits beyond the Higgins’ eye: lessons learned from their pioneering work is being used in the planning of other endangered mussel work, specifically for reintroducing the winged mapleleaf to Wisconsin rivers.
“It’s been a very fruitful and beneficial team and Wisconsin has been very prominent in the project, particularly in the early years,” Kelner said. In 2014, the Mussel Coordination Team was recognized by the U.S. Fish & Wildlife Service as a “Recovery Champion” for its work with endangered mussels.
Project biologists were from the Wisconsin and Minnesota, DNRs, Genoa Fish Hatchery, U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers.