Restoring the endangered oyster mussel (Epioblasma capsaeformis) to the upper Clinch River, Virginia: An evaluation of population restoration techniques

From 2005 to 2011, the federally endangered freshwater mussel Epioblasma capsaeformis (oyster mussel) was reintroduced at three sites in the upper Clinch River, Virginia, using four release techniques. These release techniques were (1) translocation of adults (site 1, n=1418), (2) release of laboratory-propagated sub-adults (site 1, n=2851), (3) release of 8-week-old laboratory-propagated juveniles (site 2, n=9501), and (4) release of artificially infested host fishes (site 3, n=1116 host fishes). These restoration efforts provided a unique research opportunity to compare the effectiveness of techniques used to reestablish populations of extirpated and declining species. We evaluated the relative success of these four population restoration approaches via monitoring at each release site (2011–2012) using systematic 0.25-m2 quadrat sampling to estimate abundance and post-release survival. Abundances of translocated adult and laboratory-propagated sub-adult E. capsaeformis at site 1 ranged 577–645 and 1678–1700 individuals, respectively, signifying successful settlement and high post-release survival. Two untagged individuals (29.1 and 27.3mm) were observed, indicating that recruitment is occurring at site 1. No E. capsaeformis were found at sites where 8-week-old laboratory-propagated juveniles (site 2) and artificially infested host fishes (site 3) were released. Our results indicate that translocations of adults and releases of laboratory-propagated sub-adults were the most effective population restoration techniques for E. capsaeformis. We recommend that restoration efforts focus on the release of larger (>20mm) individuals to accelerate augmenting and reintroducing populations and increase the probability for recovery of imperiled mussels.