OAKWOOD — The late afternoon sun breaks through the broad-leafed canopy of a large sycamore tree on the bank of the Salt Fork, penetrating the river's clear, swift-moving water and illuminating thousands of peanut-sized snail shells dotting the rocky river bottom Thursday.
Two of the horn snails cling to the empty shell of a large mussel sitting on the bottom.
Both indicate a healthy river, says researcher Kevin Cummings, as he wades knee-deep in the river that's bulging a bit this week, carrying recent rains from the remnants of Hurricane Isaac.
Dressed in a wet suit and water shoes, Cummings' legs push against the river's current as he slowly walks upstream, picking up a variety of mussel shells along the way. Some of the shells are empty, and some not. Some are common species, but several that Cummings easily spots are on the federal or state endangered species lists, like the wavy-rayed lampmussel, the plain pocket book mussel or the purple wartyback, whose inner shell has a purple hue.
Cummings and the other four scientists wading in the river are here to add a couple hundred more endangered mussels to the Salt Fork River.
Cummings and Jeremy Tiemann, both biologists with the Illinois Natural History Survey at the University of Illinois, were involved in a multi-state effort about three weeks ago to gather thousands of endangered northern riffleshell and clubshell mussels from the bottom of the Allegheny River in Pennsylvania for relocation to other states, including Illinois.
This week, they're relocating the first batch into the Salt Fork River, deemed a healthy, adequate environment for the endangered species. Also part of the effort are Drew Becker and Mike Coffey, both biologists with the U.S. Fish and Wildlife Service, and Sarah Bales, a biologist with the natural history survey, and one volunteer, Michael Douglas.
In a drought-stricken summer, the Salt Fork's high water somewhat surprises the scientists, who prefer a calmer river for the day's mission, but with storms in the forecast, they deal with the river conditions and take advantage of Thursday's clear skies. They decide the riffle of water near the sycamore is a good spot to "plant" the 250 northern riffleshell mussels that are patiently awaiting their return to water, sitting in two coolers that the team lugged from their vehicles to the river's edge.
Though the mussels are far from their original home in the Allegheny River in Pennsylvania, their new surroundings in this section of the Salt Fork River near Oakwood in Vermilion County won't be entirely foreign. In this same spot, somewhere along the river bottom, are most of the 70 mussels that were moved here from the Allegheny two years ago.
Monitoring of that group by the Illinois Natural History Survey and the U.S. Fish and Wildlife Service has shown a significant majority of the endangered mussels are alive and well. Their success has cleared the way for the relocation of this group of endangered mussels from the same site on the Allegheny, where a future bridge project threatens their survival.
Six feet wide at the base of its trunk and its branches towering high above the river below, the sycamore appears to have lived for ages and may have been alive when riffleshell thrived in the Salt Fork without assistance.
The team members begin to grab handfuls of mussels from the coolers and wade to the middle of the riffle, where Coffey raises one in his hand and mentions how long it's been since this species has been in this river.
"Almost a hundred years," he says. Until 2010, the northern riffleshell hadn't been seen in the waters of the Middle Fork basin — which includes the Salt Fork — since the 1920s, according to Cummings.
As if planting rice in flooded fields, the team members bend over in the knee-deep water, reaching below the surface of the swift-moving stream and drive the edge of each mussel into a gravelly spot in the river's bottom — siphon up so they can breath, and hopefully thrive.
Protruding from one side of each mussel's shell is a gray glob of hardened epoxy that surrounds a rice-sized metal transponder. A tiny number tag, corresponding to the transponder, is attached to the other side of all 350 mussels who made the trek from Urbana. The rest of the 1,200 northern riffleshell and clubshell mussels are still in holding ponds back on campus. They'll soon be planted at another river site along the Salt Fork, and possibly the Middle Fork.
The transponders allow researchers to regularly return to the river sites and, using a wand, detect the mussels and track their progress.
Within a half hour, the team finishes planting the 250 riffleshells, and they wade upstream with the second cooler in search of another spot to plant 100 clubshell mussels, also from the Allegheny and also an endangered species that's being reintroduced to the Middle Fork basin.
The group repeats the process and within an hour is wading back downstream to their original spot, with 350 mussels successfully placed in the riverbed. Across the stream from the sycamore, the group picks up the other empty cooler and hikes back to the vehicles, bringing to an end a day that started on the UI campus with the final tagging of the 1,200 mussels.
"Long day," Cummings says.