Northern Riffleshell and Clubshell 2015 Monitoring Results

In 2015, staff from the Illinois Natural History Survey continued to monitor translocated populations of two federally-endangered freshwater mussel species in the Vermilion River basin (Wabash River drainage). Between 2010 and 2014, a total of 2,099 Northern Riffleshell (Epioblasma rangiana) and 1,766 Clubshell (Pleurobema clava) have been translocated to eight sites in the Vermilion River basin, Champaign and Vermilion counties, Illinois. These translocated animals have been monitored seasonally since being moved to Illinois. For the 2015 calendar year, 36% (716) of the 1,991 available Northern Riffleshell were encountered, and of those physically examined, 61% (54 of 88) were alive. Conversely, 77% (1,359) of the 1,758 available Clubshell were encountered, and of those examined, 82% (106 of 129) were alive. The encounter and survival rates from the raw data collected in 2015 were comparable to previous years in Illinois. Throughout the duration of the project, both Northern Riffleshell and Clubshell have had higher encounter rates in the spring and autumn than summer. This relocation project is being funded, in part, by a natural resource damage assessment settlement (Hegeler Zinc—Lyondell Basell Companies) to the U.S. Fish and Wildlife Service and to the State of Illinois, and by the U.S. Fish and Wildlife Service’s Ohio River Basin Fish Habitat Partnership.