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Over the past three years, scientists from the Illinois Natural History Survey have translocated hundreds of mussels from the Allegheny River in Pennsylvania (where they lived beneath a bridge slated for demolition) to sites on the Middle Fork and Salt Fork of the Vermilion River.
The two species of mussels involved, clubshells and northern riffleshells, are both classified as “endangered” by the federal government, and by dint of that status they are subjects of recovery plans coordinated by the U. S. Fish and Wildlife Service. Those plans call for them to be reestablished throughout their historical range, which includes Illinois.
I had the opportunity recently to tag along with scientists from the Survey on a trip to check on some of those translocated mussels at a site on the Salt Fork River.
How do you check on mussels?
Under normal circumstances, it’s possible to see some of them just by looking into a stream if the water is both shallow and clear enough. That’s because mussels spend some of their time poking up from the streambed, or even entirely exposed. But mussels also spend time buried beneath the streambed, so scientists find them by “grubbing,” which is digging around in the sand and gravel with their hands.
Fortunately, checking on the translocated mussels is easier than all of that, because they had coded tags epoxied to their shells before they were placed in the river. That enables scientists to find them using an electronic reader, which looks very like a standard metal detector, and is used in much the same way.
Wielding the reader was Austin Haskett, a summer technician who is also a student in the U of I Department of Natural Resources and Environmental Sciences. He began slightly upstream of where the mussels were released last year and worked his way back and forth across the river in partially overlapping strips. Each time the reader picked up a signal, he called out the number from the display and it was recorded on an inventory list by another member of the team.
[Photos by author: Jeremy Tiemann (snorkeling) Austin Haskett and Rachel Vinsel of INHS at work; a clubshell mussel picked up for closer inspection.]
At the same time, other scientists snorkeled in the river to inspect a sampling of the endangered mussels visually.
During the day’s work, a total of 286 tagged mussels were located, just over half of the ones placed there. “That’s about what we would expect,” explained Jeremy Tiemann, the Natural History Survey field biologist who is leading the translocation effort in Illinois. “Others may have been so close together or so deep the reader didn’t pick them up. It’s also possible some moved up or downstream a little ways.”
In overall terms Tiemann is pleased with how the translocation project is going. He said, “It may be some time before we see evidence of these animals reproducing successfully, but up to now there have been no surprises.”
You may be wondering what has changed in our rivers that makes it possible to reintroduce animals that were wiped out more than a century ago. I put that question to Kevin Cummings, who is senior research scientist and curator of mollusks in the Natural History Survey’s Center for Biodiversity. “The short answer,” he replied, “is the Clean Water Act. That, and some changes for the better in agricultural practices.”
He continued, “mussels are still one of the most endangered groups of animals in North America, but the improvements we’ve seen in recent decades provide a glimpse of what’s possible when we treat our waterways with respect.”
Tune in next week to hear about the rediscovery in the Illinois River of a mussel species that hadn’t been documented there since the late 1800s.