diversity Article A Comparison of Systematic Quadrat and Capture-Mark-Recapture Sampling Designs for Assessing Freshwater Mussel Populations Caitlin S. Carey 1,2,*, Jess W. Jones 2,3, Robert S. Butler 4, Marcella J. Kelly 2 and Eric M. Hallerman 2 1 Conservation Management Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA 2 Department of Fish and Wildlife Conservation, College of Natural Resources and Environment, Virginia Polytechnic Institute and State University, 310 West Campus Drive, Blacksburg, VA 24061, USA 3 U.S. Fish and Wildlife Service, Blacksburg, VA 24061, USA 4 Asheville Field Office, U.S. Fish and Wildlife Service, Asheville, NC 28801, USA * Correspondence:
[email protected] Received: 30 June 2019; Accepted: 5 August 2019; Published: 7 August 2019 Abstract: Our study objective was to compare the relative effectiveness and efficiency of quadrat and capture-mark-recapture (CMR) sampling designs for monitoring mussels. We collected data on a recently reintroduced population of federally endangered Epioblasma capsaeformis and two nonlisted, naturally occurring species—Actinonaias pectorosa and Medionidus conradicus—in the Upper Clinch River, Virginia, over two years using systematic quadrat and CMR sampling. Both sampling approaches produced similar estimates of abundance; however, precision of estimates varied between approaches, years, and among species, and further, quadrat sampling efficiency of mussels detectable on the substrate surface varied among species. CMR modeling revealed that capture probabilities for all three study species varied by time and were positively associated with shell length, that E. capsaeformis detection was influenced by sex, and that year-to-year apparent survival was high (>96%) for reintroduced E.