2024 Volume 80 Issue 25 Article ID: 24-25023
Environmental DNA (eDNA) has attracted attention to evaluate the abundance and distribution of rare species in aquatic environments such as rivers, lakes, and sea. Recently, with the development of technologies for eDNA analysis, it has been applied for diverse purposes, including the detection of invasive alien species and the protection of endangered species. In this study, we developed an analytical assay that uses eDNA to determine the abundance of fish species to understand the habitat conditions of Masu salmon (Oncorhynchus masou), which are important fishery resources. Quantitative PCR using the TaqMan probe assay was employed to estimate the populations of the target species. The developed assay successfully provided the amount of eDNA reflecting the population density in the breeding tanks, and was established as an effective and labor-saving assay to determine the abundance of O. masou spp. To understand the migration ecology of O. masou masou, field surveys were conducted once a month from July to November 2021 at nine sites on the Akagawa River in Yamagata, Japan. The analysis of samples obtained in the survey using the developed assay demonstrated that the amount of eDNA in O. masou spp. varied significantly depending on the month (p = 0.016), reaching a maximum (1.3×106 copies/s) in October. This fluctuation indicates the effects of upstream migration and spawning activities of anadromous Masu salmon from the coastal area. The eDNA of O. masou spp. was not detected in the Otori River (AK1) throughout the study period, which was consistent with the actual habitat distribution of Masu salmon in the Akagawa River. The eDNA analysis developed in this study may be used not only to understand the seasonal migration ecology of O. masou spp. but also to identify the upper boundary of the run and spawning grounds.
