Cooperative Fish and Wildlife Research Units Program: Idaho
Education, Research and Technical Assistance for Managing Our Natural Resources

Natural resource managers are seeking appropriate chemical eradication and control protocols for infestations of dreissenid mussels, Dreissena polymorpha, D. rostiformis bugensis, that have limited effect on non-target species. Applications of low concentrations of potassium salt (as potash) have shown promise for use where the infestation and treatment can be contained or isolated. To further our understanding of such applications and obtain data that could support a pesticide registration, we conducted studies of the acute and chronic toxicity of potassium chloride to dreissenid mussels in four different sources of water sources from infested and non-infested locations (ground water from northern Idaho, surface water from the Snake River, ID, surface water from Lake Ontario, Ontario, Canada, and surface water from the Colorado River, AZ). We found short term exposure of veligers (< 24 h) to concentrations of 960 mg/L KCl produced rapid mortality in water from three locations, but veligers tested in Colorado River water were resistant. We used probit models to compare the mortality responses, predicted median lethal times and 95% confidence intervals. In separate tests, we explored the sensitivity of byssal stage mussels in chronic exposures (>29 d) at concentrations of 100 and 200 mg/L KCl. Significant and rapid mortality occurred within 10 d of exposure to concentrations of 200 mg/L KCl, regardless of water source. Mean survival of byssal mussels in 100 mg/L KCl prepared in surface water from Idaho and Lake Ontario was 4.9 or 6.9 d, respectively; however mean survival of mussels tested in the Colorado River water was > 22 d. We found the sodium content of the Colorado River water was nearly three times the concentration measured in waters from the other locations, and hypothesized that sodium concentrations may affect mussel survival. Additional trials tested mussel survival in surface water sources after supplementing water with NaCl to equivalent conductivity with the Colorado River water. Addition of NaCl was significantly effective in slowing the mortality responses to concentrations of KCl. The survival was similar to that for veliger and byssal stage mussels in Colorado River water. We recommend that any additional studies and protocols for disinfection and eradication with KCl carefully consider the water quality characteristics of treatment.