Effectiveness of EarthTec ® on killing invasive quagga mussels (Dreissena rostriformis bugenis) and preventing their colonization in the Western U.S.

Dreissena rostriformis bugensis, an invasive species, also known as the quagga mussel, was discovered in Lake Mead, NV in January of 2007. In the four years since detection, quagga mussels have created tremendous economical, ecological, and human health impacts. The mussels clog pipes, ruin boat motors, and damage recreational equipment, and once established in the lake, routine maintenance is necessary to avoid further damage. Because of quagga mussels\u27 high fecundity, planktonic veliger stage, and ability to attach to substrates with byssal threads, they have easily and swiftly spread to other lakes and reservoirs in the Lower Colorado River Basin. Several strategies have been employed to mitigate and control their spread. This thesis focuses on the most popular methods of chemical control. The first portion of the study evaluated the effectiveness of EarthTec®, a copper sulfate based biocide, on killing invasive quagga mussels (adults, juveniles, and veligers) in Lake Mead, NV-AZ, at six doses, 0, 1, 5, 10, 17, and 83 ppm. For adult mussels, 100% mortality was reached by 96 h treated with 17ppm and 83 ppm EarthTec®; by 168 h, more than 90% mortality was reached treated with 5 ppm and 10 ppm EarthTec®. For juvenile mussels, 100% mortality was reached by 48 h, 72 h, 72 h and 96h for groups treated with 83 ppm, 17 ppm, 10 ppm and 5 ppm EarthTec®, respectively. For veligers, an EarthTec® dose of 3 ppm or higher killed them within 30 min or less. The second portion of the study tested the effectiveness of EarthTec® on preventing veliger quagga mussel colonization from December 2010 to early February of 2011. Veligers were dosed with 0, 1, 2, and 3 ppm of EarthTec®. Control groups (0 ppm) had more colonized mussels than the groups treated with EarthTec® (p \u3e 0.01). Statistical analysis showed that a dose of 2.6 ppm can prevent colonization of quagga mussels in Lake Mead under the experimental conditions. The results showed that EarthTec® is effective in killing adult, juvenile, and veliger quagga mussels and is effective against preventing veliger colonization. This study contributes to the understanding of chemical options that are available for quagga mussel control and prevention