Mussel survey has mixed findings
Clams crucial to quality of state waterways
Conservation biologist Jesse Weinzinger thinks mussels are arguably the most underappreciated animals in the world.
With species names like monkeyface, fawnsfoot, snuffbox and purple wartyback, he may be on to something.
"That's part of the reason why a statewide mussel survey was absent for so long," explained Lisie Kitchel, another conservation biologist at the Wisconsin Department of Natural Resources.
Thankfully — at least for the mussels — people have begun to understand how important mussels are to the health
of aquatic environments.
And so, for the first time in more than 40 years, the DNR has completed a statewide survey, identifying the monkeyface species and all of its relatives found in Wisconsin waters.
"Mussels are the filters of our water system," Kitchel said. "They improve water quality by siphoning gallons of water per day."
During the siphoning process, mussels obtain oxygen and nutrients needed for their survival and simultaneously provide food to bottom-dwelling bugs, crayfish and snails. Siphoning also removes heavy metals like mercury and other contaminants from the water.
"Mussels are among the most sensitive animals to pollutants within the water so they're great indicators of water quality," Weinzinger added. "Mussels leave behind shells after they pass away. If we see a high abundance of dead shells, then that might be indicative of a greater water quality issue in the area."
Some diversity, some devastation
Weinzinger, Kitchel and colleagues spent the past two years gathering baseline data and insights on water flow, mussel habitats and species richness and abundance in Wisconsin waterways.
In some areas, the quantity and variety of mussels was impressive. In others, there was a marked decline in numbers or a complete absence of these water-cleaning clams.
"It was good to see what mussels are still out there and where they are," Kitchel said.
Researchers would snorkel or scuba dive in 15-minute intervals for approximately two hours to collect the animals. If they wanted to look at a site more thoroughly, they would set up a five-byfive meter grid to estimate mussel populations.
Overall, researchers collected more than 21,000 mussels from 99 sites across Wisconsin.
Large mussel populations and significant species diversity were found in the St. Croix, Manitowish, Chippewa and Peshtigo rivers.
In the Green Bay and lower Fox River regions, Weinzinger and Kitchel were surprised to find an increase in the mussel populations. Previously, poor water quality plagued these areas and decimated mussel populations. With a significant water cleanup project underway in this area, the improved water quality manifests itself in more mussels.
"Prior to the 1970s, there was a void in fish and bird species in that area," Weinzinger said. "It's exciting to see recovery of the whole system in the Green Bay area, even in regard to mussels, which are easily overlooked."
A similar population upswing was seen in the Milwaukee River basin as well, where mussel populations are rebounding from when big industry dominated the area.
Prior to the Clean Water Act in 1972, many factories carelessly dumped toxic chemicals into the Milwaukee River. These actions depleted many sensitive animals groups in the surrounding waterways that make up the Milwaukee River basin. Weinzinger said the DNR is finally started to see species return in this area, and they've even found two endangered mussel species in the system.
"Unfortunately, lower sections of the Milwaukee River basin still lack the high species diversity that we expect in similar system that doesn’t face these industrial pressures," Weinzinger said.
Southern Wisconsin waterways, such as the Pecatonica and Rock Rivers, were two of the less fortunate areas revealed by the survey. Four mussel species from the Pecatonica River previously listed as endangered and threatened were nowhere to be found — scores of dead shells were all that remained.
"These were very depressing areas," Weinzinger said. "We would go back and call the person who did the survey in the past to make sure we were in the right place — and we were — but low and behold the mussels got wiped out."
Although the survey didn't specifically address the cause of the declines, other DNR programs that monitor water quality have shown that nitrate and ammonia levels in the Pecatonica River exceed the threshold that mussels can tolerate.
Endangered animals
Freshwater mussels throughout North America are in jeopardy — Weinzinger actually called them the most imperiled animals in the world.
According to the Clam Chronicle, the biannual newsletter of the DNR's Wisconsin Mussel Monitoring Program, 30 mussel species native to North America have become extinct in the last 100 years. Seventy percent of remaining species are considered endangered, threatened or vulnerable.
Wisconsin is home to 50 native mussel species — of those, Kitchel said, 24 are endangered, threatened or listed as species of concern.
Water pollution, habitat loss, overharvesting and invasive species all contribute to this issue.
Mussels have long been treasured for their pearls and shells. Unfortunately, commercial harvesting decimated mussel numbers, and the practice has been since outlawed.
Invasive species, such as zebra mussels, are also ecological troublemakers responsible for declining populations. Zebra mussels are native to Europe and Asia, but were introduced to the Great Lakes in the 1980s. Since then, they have spread through the Midwest and now infiltrate Wisconsin river systems, making it difficult for native mussels to survive. According to Kitchel, the smaller zebra mussels are attracted to the native species, so much so that zebra mussels then cover the native species and prevent them from eating, breathing or reproducing.
Managing all of these potential risk factors is essential for species conservation.
Areas with large mussel populations and high species diversity will be kept under observation and maintained. In locations that contain older mussels but don't show signs of new life, the DNR will asses water quality to identify why young mussels aren't being produced or surviving until adulthood. In sites that lost species, the DNR may reintroduce them, with help from agencies like the Genoa National Fish Hatchery.
Kitchel and Weinzinger encouraged citizens to report any mussels — dead or alive — they encounter to complement the DNR's survey efforts.
"We want any observation of freshwater mussels because they're easily overlooked," Weinzinger said. "We have over 15,000 lakes and 84,000 miles of river in the state. Just by that number, there's a lot of data gaps that we would like to fill through citizen science or volunteer monitoring."
Citizens can report mussels using the iNaturalist mobile app or by submitting photos with pictures and information tohttps://www.inaturalist.org/projects/wisconsin-mussel-monitoringprogram. Observers are instructed to photograph mussels with the hinge side up, as shown in the picture, and then return live mussels to the water.