Jeremy K. Wise James A. Luoma Matthew T. Barbour 2018 <p>Zebra mussels (Dreissena polymorpha, Pallas, 1771) are an aquatic invasive species in the<br>United States, and new infestations of zebra mussels can rapidly expand into dense colonies. Zebra<br>mussels were first reported in Marion Lake, Dakota County, Minnesota, in September 2017, and<br>surveys indicated the infestation was likely isolated near a public boat access. A 2.4-hectare area<br>containing the known zebra mussel infestation was enclosed and treated by area resource managers for<br>9 days with EarthTec QZ (target concentration: 0.5 milligrams per liter as copper), a copper-based<br>molluscicide, to eradicate the zebra mussels. Researchers led an onsite bioassay to provide an estimate<br>of the treatment efficacy within the enclosure. The bioassay was conducted in a mobile assay trailer that<br>received a continuous flow of treated lake water. Bioassay tanks (n=9; 350 liters) within the trailer were<br>stocked with zebra mussels (25 mussels per containment bag; 7 bags per tank) collected from White<br>Bear Lake, Ramsey County, Minn. Mortality in the treated bioassay tanks reached a mean of 99 percent<br>(95-percent confidence interval: 98–100 percent), there were no mortalities in the control tanks.<br>However, a predictive model produced for timely delivery to area resource managers indicated zebra<br>mussel mortality within the treated enclosure may have been as low as 85 percent. Onsite bioassays are<br>a viable and important tool for treatment evaluation particularly in newly infested waterbodies with low<br>zebra mussel densities.</p> application/pdf 10.3133/ofr20181138 en U.S. Geological Survey A bioassay assessment of a zebra mussel (Dreissena polymorpha) eradication treatment reports