Use of environmental DNA to survey the distribution of the invasive mussel Limnoperna fortunei in farm ponds

: The golden mussel Limnoperna fortunei (Dunker, 1857) is an invasive freshwater bivalve species that exerts harmful effects on the environment, as well as man-made structures, such as water-treatment systems. By using conventional sampling methods, it is difficult to detect mussels under low-density conditions; however, environmental DNA (eDNA) analysis may be a rapid and efficient method for monitoring this aquatic organism. In this study, we conducted surveys based on the eDNA analysis of L. fortunei in 15 farm ponds in Japan and compared the results with those of two conventional survey methods, visual census and plankton larval survey, to clarify the effectiveness of eDNA analysis for field surveys of L. fortunei . Primers and a probe specific to L. fortunei were developed, and a method for analysis was established. In the laboratory experiments, the species eDNA was detected in all water tanks containing the mussels, and the concentration of eDNA was high in the experimental tank that had high density of L. fortunei . In the field survey, L. fortunei eDNA was detected in all ponds where the mussels were found by conventional survey, and low concentrations of eDNA were also detected in several ponds where no L. fortunei were found by traditional methods. These results suggest that eDNA analysis has greater sensitivity for the detection of L. fortunei in farm ponds than that of conventional methods. Environmental DNA surveys have little impact on water management and are suitable for surveys at water facilities that have not yet been damaged by the mussels.