Scatter plot of the numbers of fish species detected from the fish eDNA metabarcoding. The numbers were not corrected for the filtered volumes (1000 mL for Sts. 2–5 and 600 mL for Sts. 1, 2) and are plotted against latitudes. Orange, blue, and green dots represent the data from sandy-shore, rocky-shore, and inner-bay areas, respectively. Note that the rocky-shore areas are mostly located along the southern coastline, while sandy-shore and inner-bay areas are located in the northern coastlines of Boso Peninsula. Thus, the gradient of the species richness does not necessarily relate to latitudes.