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Conditions for life in the Illinois River have changed dramatically since the middle of the 20th century, thanks in large part to the Clean Water Act. For example, surveys of the upper river in the 1960s by researchers looking for mussels, a.k.a. freshwater clams, failed to yield even a single live specimen. In contrast, surveys of the same area conducted in the 1990s, turned up hundreds of mussels representing no fewer than 18 species.
a collection of state and federal agencies got a unique opportunity to check on the status of mussels in the upper Illinois River in May of this year when the water level was lowered for inspection and repair of the dam at Marseilles. Instead of using scuba gear and other specialized equipment, as they would under normal conditions, they were able to boat from one exposed shoal to another, and walk around to collect mussels.
Even the people most familiar with the river were not ready for what they found. In the words of Rich Lewis of the Illinois Department of Natural Resources, “everybody was just shocked at the number of mussels.”
[Photos: sorting mussels on an exposed shoal; Kevin Cummings in the mussel collection at INHS holding the shell of the scaleshell mussel.]
In the course of two days, the census and salvage operation collected nearly 15,000 live specimens. And there were many more where those came from; there just wasn’t enough time or manpower to get all of them. Among the total were representatives of 23 species, fiver more than were found in the 90s.
The exposed bed of the Illinois River had another shock for scientists, too.
It was one of the last live mussels picked up at one of the last sites they visited, a mussel known by the unprepossessing name, “scaleshell.”
Few people would have recognized they were holding anything special, but the scaleshell was found by Kevin Cummings, who is Senior Research Scientist and Curator of Mollusks for the Illinois Natural History Survey at the U of I Prairie Research Institute. He has spent decades assessing museum collections around the world to create an accurate database of Illinois mussels.
“One of these things is not like the others,” is what he told me he thought when he picked it up. Without any prompting from Cummings, his crew came up with the same identification, and that was later confirmed with DNA analysis conducted by Kevin Roe of Iowa State University, an authority on the genetics of the scaleshell.
Scaleshells were historically found in the Mississippi and Ohio River drainages, from Minnesota in the north to southern Arkansas in the south, and they were widely distributed in the bigger rivers of Illinois. But none have been documented in the state for more than a century.
Up until Cummings’ discovery, the only known remaining populations of scaleshells, which are federally endangered, were in Missouri, Arkansas and Oklahoma.
People who aren’t normally concerned with mussels might wonder why others get excited to know they are coming back, as both the large numbers and presence of rare species in the Illinois River suggest.
Cummings explains by comparing mussels in a river to canaries in a coalmine. “When they begin to decline, we know there are problems in the system. When they come back, we know we’re headed in the right direction.”
Author's note: a longer version of this piece ran in the Champaign News-Gazette on July 7, 2013: