Monitoring Translocated Northern Riffleshell and Clubshell in Illinois

The recovery plan for the federally-endangered Northern Riffleshell (Epioblasma rangiana) and Clubshell (Pleurobema clava) listed an objective of establishing viable populations of the species in ten separate river drainages throughout their respective ranges. The recovery plan stated that population augmentations and reintroductions would be needed to achieve this objective, and the Vermilion River (Wabash River drainage) in Illinois was agreed upon as a potential location for reintroduction. Beginning in 2005, Illinois partnered with the U.S. Fish and Wildlife Service and state agencies in Ohio and Pennsylvania and began planning the release of these species into the Vermilion River. The goal was to re-establish self-sustaining Northern Riffleshell and Clubshell populations to their historical ranges in Illinois. A bridge construction project has provided an opportunity for the translocation of both species from Allegheny River, Forest County, Pennsylvania, to the Vermilion River basin, Champaign and Vermilion counties, Illinois. Animals were moved in 2010, 2012, and 2013, and all animals were affixed with passive integrated transponder tags, which have allowed researchers to monitor the animals. To date, 1,349 Northern Riffleshell and 958 Clubshell have been translocated to eight sites in the Vermilion River basin (five in the Middle Fork and three in the Salt Fork). Since the inception of the monitoring program, the detection rate per survey per site has varied from 18% to 100% for the Northern Riffleshell and from 37% to 100% for the Clubshell. Of the individuals encountered and inspected during the duration of the project, 56% of the Northern Riffleshell and 78% of the Clubshell have been alive. 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.