Evaluation of watercraft quagga mussel decontamination in saltwater

Abstract

Listen

Translate article

Restricting the spread of invasive quagga and zebra mussels by decontaminating recreational watercraft is an important management practice in Europe and the United States. These mussels impact freshwater ecosystems and leave massive economic costs of restoration for ecological services and human infrastructure for each water body they invade. The authors investigated, at the request of the California Department of Fish and Game, whether decontaminating watercraft by placement into saline waters after coming into contact with freshwater bodies infested with invasive mussels eliminates the risk of spreading the species. Evaluating whether or not this is a viable management practice is critical where zebra and quagga mussel freshwater habitats are directly connected to brackish and saline water bodies, like the SacramentoSan Joaquin River Delta (Delta), California United States of American (USA). In this study, quagga mussels were exposed to water collected from different locations within the Delta, with salinities ranging from 4 parts per thousand (ppt) to 33.4 ppt for up to fifteen days. We observed a mortality gradient correlating to salinity levels. The water with the highest salinity content killed 100% of the quagga mussels within 40 hours. One hundred percent mortality was not observed until 70 hours of exposure for quagga mussels exposed to lower salinity concentrations of 21.3 ppt and 15.3 ppt. However, 99% of mussels exposed to 4.0 ppt salinity brackish water remained alive for the 16 day duration of the study. These results are similar to mussels held in water with low salinity content similar to most freshwaters. In the Delta, salinity fluctuates naturally and travel time by boat between saline and freshwaters is a few hours or less. Therefore, it would be challenging if not impossible for watercraft operators to ensure the proper exposure time and salinity exposure. Based on these results, the authors do not recommend launching boats into salt water or brackish water prior to entry into freshwater as a decontamination option for watercraft or as a management tool for preventing invasive mussel infestations.