Environmental Almanac: Rare mussel found in Illinois River
When seven barges broke free from their tow and slammed into the dam on the flooded Illinois River at Marseilles in mid-April, few people were in a position to see an upside to the story. Some weeks later, however, when the U.S. Army Corps of Engineers made known plans to draw down the river level to inspect and repair damage from the incident, Randy Timmons saw both catastrophe and opportunity.
Timmons, who is a district forester with the Illinois Department of Natural Resources (IDNR), realized that the drawdown on the Illinois would strand significant numbers of mussels as the shoals and banks where they live were exposed — a catastrophe for them, but also an opportunity for scientists who would study them.
Under normal conditions, a mussel survey on the Illinois River requires scuba gear and other specialized equipment, and sampling can be hit or miss even for a well-outfitted effort. With the river so low, however, scientists would be able to walk on dry land and have access to more mussels than they could possibly collect.
So Timmons reached out to Kevin Cummings, senior research scientist and curator of mollusks at the Illinois Natural History Survey (INHS), and Rich Lewis, who reviews environmental plans for IDNR and is one of the few certified divers who surveys mussels in the state. With cooperation from others, the two of them planned a two-day operation to census and salvage the mussels exposed by the drawdown.
The operation took place on May 13 and 14 on a 10-mile stretch of river from Marseilles upstream to Morris, with water levels 6-8 feet below normal. In all, it involved five boats and about 25 people, from groups including INHS, IDNR, the U.S. Fish and Wildlife Service, the Army Corps and Western Illinois University.
They worked in teams of four to six, gathering mussels in gunnysacks and then counting and sorting them according to species. Afterward, the mussels were returned to parts of the river where water still flowed.
"It wasn't rocket science," said Cummings, commenting on the work. "But we did make sure someone from each group was capable of identifying the different species with confidence."
With so much streambed exposed, Cummings emphasized, there was no thought of covering it all. Instead, the teams would spend a half hour or so at a location and then skip ahead a half-mile or so. They reasoned they could gather more useful information and do more good for the overall mussel population by hitting a select number of spots representing the different facets of the river.
To understand the significance of what the group found as they worked, you have to understand this: Only 50 years ago, the upper Illinois River was dead, at least as far as mussels were concerned. A survey conducted in 1966 found no live mussels at all between its beginning at the confluence of the Des Plaines and Kankakee rivers and Starved Rock. None.
That was in a stretch of water where 34 different species had been collected back before 1900.
Much of the life in the Illinois River was extinguished in the first two decades of the 20th century thanks to sewage and industrial waste from Chicago, which began flowing through it with the opening of the Chicago Sanitary and Ship Canal in 1900.
By 1966, conditions for life had improved a bit from their low point, as a result of state regulations and improved sewage treatment, but they were still not good enough for mussels to live in the upper river.
Further improvements in water quality followed from the Clean Water Act (passed in 1972), and by the 1990s, scientists collecting mussels in the upper Illinois turned up hundreds of mussels representing 18 different species.
Of course, that was collecting by the usual means, since the mussels were at the bottom of the river — mostly by hand while scuba diving.
The work of collecting was much easier in May of this year when the streambed was exposed by the drawdown. Even the people most familiar with the river were not ready for what they found. As Lewis put it, "I think everybody was just shocked at the number of mussels."
In the course of two days, the census and salvage operation collected 14,850 live mussels. And to be clear, there were many more where those came from; there just wasn't enough time or manpower to get them all.
Among the total were representatives of 23 species. Ninety percent of the total number of animals was accounted for by just four species, know by the common names "three-ridge," "pink heelsplitter," "fragile papershell" and "mapleleaf." Among the remainder, the eight least-common species were represented by fewer than 10 individuals, and there were just single specimens of four of those.
The exposed bed of the Illinois River had another shock for scientists, too.
It was one of the last live mussels picked up by Cummings at the last site he visited, a mussel known by the unprepossessing name "scaleshell."
Few people in the world would have recognized they were holding anything special, but Cummings 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 INHS crew came up with the same identification, and that was later confirmed by DNA analysis by Kevin Roe of Iowa State University, an authority on the genetics of the scaleshell.
Scaleshells were historically found in the Mississippi River 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 of them and presence of rare species in the Illinois River suggest.
Cummings explains by comparing mussels in a river to canaries in a coal mine. "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."
Environmental Almanac is a service of the University of Illinois School of Earth, Society and Environment, where Rob Kanter is communications coordinator. Environmental Almanac can be heard on WILL-AM 580 at 4:45 and 6:45 p.m. on Thursdays.