Effects of carbon dioxide on juveniles of the freshwater mussel Lampsilis siliquoidea (Unionidae).

Carbon dioxide has shown promise as a tool to control movements of invasive Asian carps. We evaluated lethal and sublethal responses of juvenile fat mucket (Lampsilis siliquoidea) mussels to carbon dioxide concentrations (43–269 mg/L, mean concentration) that are effective for deterring carp movement. The 28-d LC50 value (lethal concentration to 50% of the mussels) was 87.0 mg/L (95% confidence interval, CI 78.4–95.9) and at 16-d post-exposure was 76.0 mg/L (95% CI 62.9–90.3). A proportional hazards regression model predicted that juveniles could not survive CO2 concentrations 160 mg/L for more than 2 weeks or 100 mg/L CO2 for more than 30 days. Mean daily shell growth was significantly lower for mussels that survived carbon dioxide treatments; however, growth during the post-exposure period did not differ among treatments, indicating recovery of the mussels. Carbon dioxide also caused shell pitting and erosion of the periostracum in mussels. Behavioral effects of carbon dioxide included movement of mussels to the substrate surface and narcotization in the highest concentrations. Mussels in 110 mg/L, mean CO2 had the most movements, particularly in the first 3 days of exposure. If carbon dioxide is infused continuously as a fish deterrent, concentrations below 76 mg/L are recommended to prevent juvenile mussel mortality and shell damage. Mussels may survive and recover from brief exposure to higher concentrations.