Survival and Growth Rate of Translocated Freshwater Mussels <i>Lampsilis fasciola</i> and <i>Medionidus conradicus</i>

Freshwater mussels (Family Unionidae and Margaritiferidae) are a widely threatened group of bivalve molluscs, particularly in the Southeastern United States. Translocation of freshwater mussels is an increasingly common conservation method. However, there are relatively few studies that quantitatively investigate the factors influencing translocation success or failure. In October 2013, hundreds of Medionidus conradicus and Lampsilis fasciola were translocated to the Pigeon and Nolichucky Rivers in Tennessee, with an interim partial survey (June 2014) and a full survey (October 2014). In this study, I analyze this field-collected data to determine the mechanism(s) that currently influence the outcomes of Tennessee mussel translocation.

My recommendations for future surveys include open and timely data sharing between investigators and the scientific community at large. Given these data and associated collection methods, a better understanding of freshwater mussel communities and restoration success factors can be identified at lower future costs and facilitate longer-term research. My research recommendations include more frequent, complete surveys, and quantitative analyses at the mussel and community levels.

The results of this study have implications for conservation translocation efforts. My results indicate that both L. fasciola and M. conradicus can be successfully translocated to the Pigeon River, if 1) they are translocated to the Pigeon where it has less boulder, cobble and exposed bedrock in favor of more coarse and fine gravel and sand; 2) it had lower peak and average water discharge rates, 3) if some translocations occurred in the spring-early summer, and 4) if the translocated mussels are initially housed in cages or silos. The non-housed mussels were not recovered, primarily due to high water volumes and velocities soon after the beginning of the study. The housed mussels were protected. There is no overall predictability of the water discharge timing and size of the Waterville Hydroelectric Power plant’s dam. A management recommendation is for incremental releases and notification to conservation authorities. Due to significant mortality in the first 8 months of this study, some studies should start in the spring-early summer rather than in October to help translocated mussels survive their first over-winter by having some growth and habitat acclimation underway.