To test the feasibility of a citizen science program for fish eDNA metabarcoding in coastal marine environments, we recruited six groups of voluntary citizens for a science education course at a natural history museum. We held a seminar on eDNA and a workshop for seawater sampling and on-site filtration using syringes and filter cartridges for the participants. After that, they selected single survey sites following the guidelines for conducting a safe field trip. They performed seawater sampling and on-site filtration at these sites during their summer holidays. The six selected sites unexpectedly included diverse coastal habitats within a 40 km radius, located at temperate latitudes in central Japan (~35°N). After the field trips, they returned filtered cartridges to the museum, and we extracted eDNA from the filters. We performed fish eDNA metabarcoding, along with data analysis. Consequently, we identified 140 fish species across 66 families and 118 genera from the six samples, with species richness ranging from 14 to 66. Despite its limited sample size, such a diverse taxonomic range of fish species exhibited spatial biodiversity patterns within the region, which are consistent with species distribution. These include north-south and urbanization gradients of species richness, geographic structure of the fish communities, and varying salinity preferences of the component species. This case study demonstrates the potential of fish eDNA metabarcoding as an educational and scientific tool to raise public awareness and perform large-scale citizen science initiatives encompassing regional, national, or global fauna.
