Spatiotemporal Changes of the Environmental DNA Concentrations of Amphidromous Fish Plecoglossus altivelis altivelis in the Spawning Grounds in the Takatsu River, Western Japan

The Ayu Plecoglossus altivelis is an amphidromous fish that not only the most important commercial fishery species in Japanese rivers but also has a high economic value recreational fishing. However, degradation of its spawning grounds caused decrease abundance. In this study, we used environmental DNA (eDNA) to monitor Takatsu River Japan (1) identify season three known grounds, (2) clarify changes main during season, and (3) discover unknown grounds. We collected 1 L surface river water at nine times 2018 seven 2019 lower reaches River. samples from sites 2018. were filtered through glass fiber filters. Total eDNA was extracted each sample Real-time quantitative PCR performed with specific primers probe for Ayu. results analyses showed November September 2019. One site as ground both early late depending on year. At second site, frequency use changed year by third middle every From these results, elucidated some are regularly year, while others varies five sites, nighttime concentrations least once four surveys, suggesting may have functioned particular, one could be new ground.