Development of Sampling Protocols for Freshwater Mussel Density Estimates in the Meramec River Basin, Missouri

Freshwater mussels are among the most threatened aquatic fauna in North America. Given the need for monitoring and assessment of threatened populations, estimating bias of metrics from visually-based sampling methods is essential. We surveyed 15 sites in the Meramec River Basin in East Central Missouri. At each site, we employed three visual methods for estimating abundance; timed visual searches, systematic strip transects, and stratified randomly placed visual .25 m² quadrats. We excavated substrate at each .25 m² quadrat to determine abundances for each species, and eliminate the influence of visual bias. We compare the results of abundance estimates of each of the visual methods with the results of excavated quadrat samples. Sampling efficiency of visual methods was calculated and used to determine if visual techniques provide reasonable approximation of overall mussel abundances. These results will inform standardized sampling protocols for freshwater mussels for the state of Missouri.