Application of eDNA methods to evaluate abundance and reproduction of winter-breeding freshwater mussels (Buldowskia iwakawai) in the Ishikari River floodplain.

Freshwater mussels (Order Unionoida) can provide crucial ecological functions and services. However, many of them are endangered worldwide due to local extirpation and reproductive failure, which emphasizes the importance of mussel life cycle monitoring, including reproduction. Buldowskia iwakawai (Suzuki, 1939) is one such species native to the Ishikari floodplain oxbow lakes where its reproductive failure was recently reported. In this study, a species-specific environmental DNA (eDNA) assay was developed to monitor B. iwakawai abundance and winter reproduction in the laboratory and natural environment simultaneously even at times when natural lakes are covered by ice. A positive CPUE-eDNA correlation was observed across all the 14 lakes sampled prior to ice cover formation. The eDNA concentration significantly differed between gravid and non-gravid mussels in relation to their metabolic-rate differences in laboratory experiments, but the eDNA concentration increase was not detected in the intensively monitored lakes during the glochidia release period. PCR inhibition in natural water has been suggested, and reducing its effects combined with appropriate seasonal contexts has the potential to improve the applicability of this method. This research sheds new light on the applicability of the eDNA assay for monitoring mussel reproductive activities throughout their life cycle including the winter season. [ABSTRACT FROM AUTHOR]