Evaluation of Stream Reaches for Mussel Reintroduction in the Upper Coosa Watershed, NW Georgia

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The Conasauga River in northwest Georgia and southeast Tennessee harbors the majority of mussel diversity still found in the Georgia portion of the Upper Coosa Basin. While the Conasauga historically supported at least 44 mussel species, only about 20 species remain. 

Evaluation of Stream Reaches for Mussel Reintroduction in the Upper Coosa Watershed, NW Georgia

Upper Coosa Watershed, NW Georgia

PROJECT COMPLETED

The Science Issue and Relevance: The Conasauga River in northwest Georgia and southeast Tennessee harbors the majority of mussel diversity still found in the Georgia portion of the Upper Coosa Basin. The Conasauga historically supported at least 44 mussel species (15 percent of North American fauna), but only about 20 species remain. Seven of these are federally-listed, and three others are listed as endangered by the State of Georgia. Mussel populations in the Conasauga River declined sharply in the late 1900s, with a 33% loss in species richness between 1967-1973 and 2005-2006. Fish populations, historically, were relatively stable in the river, but over the past 10 years, results of repeated surveys indicate several fishes that are hosts for mussel larvae (glochidia) have declined significantly. Comparable declines have not been observed in nearby Etowah, Coosawattee, or Oostanaula rivers, which support similar fish communities. Contaminant levels, dissolved oxygen levels, and agricultural best management practices in the Conasauga are currently being evaluated, but, given the uncertainties of mussel survival in the Conasauga, establishment of new populations (within their historical range) in the Etowah, Coosawattee, and Oostanaula watersheds needs to be evaluated.

Evaluation of Stream Reaches for Mussel Reintroduction in the Upper Coosa Watershed, NW Georgia

Silos were deployed during stressful conditions for mussels to collect data. 

Methodology for Addressing the Issue*: The study area for this project includes the Georgia portion of the Upper Coosa watershed. Approximately 10 sites will be evaluated throughout the Etowah, Lower Coosawattee, and Oostanaula watersheds as potential reintroduction locations. A control site within the Conasauga watershed will be chosen based on the presence of recruiting populations of federally-listed mussel species. Each potential reintroduction location will be evaluated based on historical mussel occurrence, host fish availability and watershed integrity. Within suitable stream reaches, the 10 sites will be chosen based on habitat stability, substrate type and accessibility to deploy and monitor mussel silos. Each site will include three independent silos with 10 propagated individuals per silo. Silos will be deployed for 8 weeks during late summer when flows are typically low and conditions are stressful for mussels. Growth and survival of individually tagged mussels will be monitored at 4-week intervals. Water temperature will be continuously monitored at each site for the duration of the experiment and available stream gage data will be utilized to monitor flows.

Two silo trials will be conducted as part of this project. The initial silo trial will include evaluation of all 10 study sites and the control site using a non-listed species (i.e., Villosa nebulosa). Based on results from the initial silo trial, a subset of sites (including the control) will be selected for a follow-up evaluation, potentially using a federally-listed species (i.e., Pleurobema hayleyianum). Results from the study will be used to guide the development of a site plan for reintroducing listed mussels into the Upper Coosa watershed.

Future Steps: Life history studies and further development of propagation techniques are needed for most of the federally-listed taxa within the study area. Highest priority is the Coosa Moccasinshell, Medionidus parvulus, with only two known populations. Additional surveys to quantify abundance and composition of known mussel populations and to locate additional populations throughout the Upper Coosa are needed and will be required by the U.S. Fish and Wildlife Service following any recovery effort that includes translocation, augmentation, or reintroduction. 

*Due to vandalism and other monitoring problems, no analysis of data was performed and no products resulted from this project.