Staff from the Illinois Natural History Survey participated in a joint project with the Illinois Department of Natural Resources and the U.S. Fish and Wildlife Service to reintroduce the federally-endangered Northern Riffleshell (Epioblasma rangiana) and Clubshell (Pleurobema clava) to Illinois. A salvage project in the Allegheny River, Pennsylvania provided an opportunity for the translocation of both species. Since the first translocation in 2010, a total of 3,699 Northern Riffleshell and 4,166 Clubshell were collected from the Allegheny River at the U.S. Highway 62 (=Hunter Station) Bridge, Tionesta Township, Forest County, Pennsylvania, and translocated to suitable habitat at eight sites in the Vermilion River basin (Wabash River drainage) in Champaign and Vermilion counties, Illinois. Our monitoring data suggest the Clubshell translocation has been more successful than the Northern Riffleshell translocation. We estimate that Clubshell have approximately 5 times greater survival rates compared to Northern Riffleshell. As a result, very few Northern Riffleshell likely remain. Survival also varied among translocation sites, likely a result of localscale differences such as substrate or gradient. Regardless, high discharge events posed the greatest threat for the long-term success of this project, as survival was significantly decreased following periods of abnormally high flows. Consequently, we believe that repeated translocations of individuals over a period of several years across several sites could be implemented to reduce the overall risk of failure due to high discharge events or local-scale differences. This translocation 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.
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