数値シミュレーションを用いた魚類の環境DNA分解速度推定の試み～伊勢湾口的矢湾を対象として～

抄録

Environmental DNA (eDNA) metabarcoding is a useful method for detecting fish fauna in areas where fish sampling is difficult. Limited information on factors such as decay rate that can determine the distribution of eDNA, limits the ability to estimate the actual distribution of fish fauna using eDNA measurements. Therefore, to estimate the fish fauna in Matoya Bay, which is a typical estuary located at the mouth of Ise Bay, we used eDNA metabarcoding. The ecological characteristics of the fish fauna detected (freshwater, brackish water, and saltwater) agreed well with the salinity distribution, indicating that eDNA was degraded and transported from the mouth of the bay near the open sea to brackish water Izounoura. Based on these observations, we calculated the diffusion of eDNA of marine fish based on a flow field obtained by a numerical simulation and attempted to estimate a decay rate that closely resembled the observed distribution of eDNA concentration. The estimated decay rate constants ranged from 0.0 to 0.4 per day, which were smaller than those estimated in previous studies based on rearing experiments (0.603 to 1.653 per day). This study demonstrated the possibility of estimating decay rate constants using field observations and numerical simulations rather than rearing experiments.