In less than two days last week, the endangered mussel population in the Vermilion River system increased by 1,000. It wasn't a natural phenomenon, but the work of a team of local scientists.
DANVILLE — In less than two days last week, the endangered mussel population in the Vermilion River system increased by 1,000.
It wasn't a natural phenomenon, but the work of a team of local scientists who gathered endangered clubshell and riffleshell mussels from the bottom of Pennsylvania's Allegheny River last week, and by Friday, transplanted them into the Vermilion River system, where the hope is that they will thrive and eventually multiply on their own.
A large mussel bed with as many as 200,000 animals, including endangered clubshell and riffleshell, exists in a section of the Allegheny River beneath a bridge on U.S. 62 in northwestern Pennsylvania. The bridge is slated for replacement in 2016, and when the old structure is dropped into the water, it could kill the mussels below. In 2008, Pennsylvania state agencies along with the U.S. Fish and Wildlife Service, began relocating as many as possible to other states.
In 2010, about 150 clubshell and riffleshell were relocated to the Vermilion River system, which includes the Salt Fork, Middle Fork and North Fork branches that stretch from western Champaign County to Vermilion County, and eventually converge into the Vermilion River that flows into the Wabash River in western Indiana. The Vermilion River is part of the endangered mussels' native range, and scientists identified it as an area that could support reintroduction of these two species.
The small batch did well in its new Illinois digs, so last year, federal wildlife officials granted permission for another 1,200 to relocate to sites in the Vermilion River.
Monitoring of that batch has also been promising.
So in a sequel to last year's relocation effort, a team of local scientists led by Jeremy Tiemann with the Illinois Natural History Survey at the Prairie Research Institute at the UI, traveled to Pennsylvania last Sunday. They dived for mussels Monday, gathering 750 clubshell and 250 riffleshell, rushed them back to the UI on Tuesday, quarantined and tagged them, and Thursday and Friday, transplanted them in five sites in the Vermilion River system.
"It's been a bang, bang week," said Kevin Cummings, a research scientist with the Illinois Natural History Survey, just after the team had finished transplanting the last of the mussels on Friday.
During their quarantine, a passive integrative transponder was attached with epoxy to each mussel. The transponders send out a radio signal that the scientists can monitor the mussels' progress at the transplant sites. After a year and a half, about 80 percent of the original 150 mussels were located again by researchers.
"We're going to establish a few more sites this year to spread them out, so we can get away from putting our eggs in one basket," said Tiemann, who explained that there are five sites altogether in the Salt Fork and Middle Fork rivers. "We do expect some mortality, but our (survivor) numbers are on par with Ohio and West Virginia and other states. It's working out pretty well. It's been a great project so far."
But the ultimate goal isn't for the transplanted mussels to survive but reproduce and that will take time to measure, according to Tiemann, who explained that the mussels have a complex reproductive process that takes time to establish. He said juveniles bury into the river substrate, so in two to three years, scientists will go back to the sites to search for, and hopefully find, buried juveniles, which would be a good indicator.
"Unfortunately, we won't know if it's a success for 10-15 years. If we are successful," he said, "our project will be another step in recovering these species with the ultimate goal of being able to delist them."
Funding for this third relocation to the Vermilion River system comes from a Natural Resource Damage Assessment settlement that was a result of contamination at the former Hegeler Zinc smeltering facility, a 100-acre site about 3 miles south of Danville off Illinois 1 that the U.S. Environmental Protection Agency made a Superfund cleanup site several years ago.
A zinc smeltering facility operated there from 1906 to the 1950s and included a 5-acre slag waste pile that contained lead, arsenic and other heavy metals, according to a 2001 investigation conducted by the Illinois EPA. Hazardous substances from the site were released into Grape Creek, which flows into the Vermilion River a few miles downstream of the hazardous waste site. Through the process the state EPA and Illinois Department of Natural Resources received a settlement as compensation for damage to natural resources along the Vermilion River watershed, and a portion of the settlement funds are being used to support the mussel reintroduction effort.
Tiemann and Cummings said there should be funding to relocate another group of mussels next year. Tiemann said all these trips are to establish multiple age classes of mussels, and the more they go out, the more variety of ages of animals they can get to add to the population here.
Tiemann said it's a lot of driving and work in a short of amount of time.
"But it's definitely worth it," he said.
About freshwater mussels
Mussels are often referred to as "the livers of the rivers" because of their ability to filter particles and contaminants from the water.
Mussels are also an important part of the food web, consuming detritus, bacteria and plankton and in turn being eaten by minks, otters, muskrats, raccoons, birds, and fish.
Species like the northern riffleshell are sensitive to environmental conditions and serve as a "canary in the coal mine" — population declines can indicate problems with water quality.
Riffleshell and clubshell mussels are freshwater mussels, which are one of the most endangered groups of animals in North America. Several factors are thought to be responsible for the decline of mussel populations, including overharvest, siltation of their habitat from agriculture, competition from exotic species like the zebra mussel and pollution by herbicides, pesticides and other chemicals. As a result, many mussels have been designated as state-endangered or federally endangered species.
Mussels live in the mud, sand or gravel in rivers and streams with some found in ponds or lakes. When mussels reproduce, their larvae, or glochidia, are expelled into the water to attach to a host, usually a fish, connecting to the gills or fins. Some mussels are host-specific while others use a wide variety of fish.
While attached, the larvae change form and begin to resemble adults. Eventually the small, young mussels break free and drop to the stream or lake bottom to begin an independent life.
Source: Illinois Natural History Survey