URBANA — Last summer, research scientists with the Illinois Natural History Survey moved 1,200 endangered northern riffleshell and clubshell mussels from Pennsylvania to the Salt Fork and Middle Fork rivers and are now searching for two more sites in the Vermilion River system to move more.
Jeremy Tiemann with the Illinois Natural History Survey said officials are looking for a good site along the North Fork branch of the Vermilion River in Vermilion County and a second site along the Middle Fork.
In 2005-06, the Illinois Department of Natural Resources and the U.S. Fish and Wildlife Service implemented a plan to restore the northern riffleshell and clubshell species to their historical portions and ranges in Illinois, and the Middle Fork River was chosen as a target basin for the project.
While Illinois was launching that plan, Pennsylvania officials were needing to relocate a large population of riffleshell and clubshell mussels from a part of the Allegheny River beneath an bridge that will be demolished and replaced in the next few years. The old bridge will be dropped into the water, which could kill the mussels, so Pennsylvania state agencies and the U.S. Fish and Wildlife Service are relocating them.
Riffleshell and clubshell mussels are freshwater mussels and are one of the most endangered groups of animals in North America and a good indicator of water quality. Surveys in the past few decades have identified significant declines in mussel populations for various reasons, but thousands thrive in the Allegheny River near the bridge project, motivating environmental officials to save as many as possible. More than 50,000 mussels inhabit the area near the bridge that carries U.S. 62 over the Allegheny in Franklin, Pa.
In 2010, the first batch of northern riffleshells, about 140, were delivered to East Central Illinois; half went to the Middle Fork and the other half to the Salt Fork. After a year and a half, 80 percent were still alive, a good survival rate, so U.S. Fish and Wildlife officials approved the relocation of more.
In August, a team of local environmental officials went to the Allegheny and gathered another 1,000 northern riffleshell and 200 clubshell mussels, transported them to the University of Illinois campus, where they were quarantined in holding tanks with flowing water, and eventually moved them to designated sites on the Salt Fork and Middle Fork rivers.
Now, Tiemann said, there's the opportunity to relocate more mussels, and he and other local officials are in search of good spots along the Middle Fork and North Fork rivers.
The previous sites were chosen based on fish density and whether they were protected land, such as park property. Both the riffleshell and clubshell need certain types of fish to survive, because their larvae attach to the gills of fish. The northern riffleshell needs the bluebreast darter, which is also an endangered species, but northern riffleshell larvae can also attach to other darters. The clubshell needs a variety of minnows, but may use darters, too. Darters are found in the Vermilion River system.