高知県奈半利川におけるアユ人工産卵場の利用状況モニタリング～潜水目視調査と環境DNA分析の比較を中心に～

抄録

Establishment of an artificial spawning ground was started in 2003 at the Nahari River that flowing in the southeastern part of Shikoku, Kochi Prefecture, Japan, as an effort to conserve the natural resources of Plecoglossus altivelis altivelis. The results of the resource survey show that the number of drifting larvae increased remarkably and the number of upstream migrating juveniles increased and stabilized since 2005. The results of the survey of spawning in artificial spawning grounds show that P. altivelis altivelis uses the artificial spawning grounds as the main spawning ground every year. In addition, the results of environmental DNA analysis show high eDNA concentration in the samples downstream of the artificial spawning ground during the spawning season. Furthermore, during the peak spawning season, the eDNA concentration of the nighttime sample was approximately 25-fold higher than that of the daytime sample downstream of the artificial spawning ground.