Kaede Miyata, Yasuaki Inoue, Natsumi Kitazaki, Keisuke Nakane, Fumihito Kato, Hiroyuki Konishi, Masayuki Yamane, Koji Mine, HIROSHI HONDA

The use of environmental DNA for molecular ecological surveys has become widely utilized in ecological assessments of various water environments, from rivers to coastal and marine areas. However, it is important to consider the scenarios of potential contamination of environmental nucleic acids in interpreting the results. In this study, we analyzed the fish species present in the feed that may affect surveys near aquaculture facilities and fish processing plants using metabarcoding analysis of environmental DNA/RNA, and simultaneously evaluated whether the fish species present in the feed used for aquaculture in a heavily cultivated bay could be detected through metabarcoding analysis, thus evaluating whether fish species present in the feed could be detected in ecological surveys in the marine environment. A total 51 fish species (DNA: 46, RNA: 31) were detected in three type of fish feeds; detected species in DNA were more than those in RNA and common species that detected in both of feeds and water samples in the bay is remarkably more in eDNA than eRNA. Moreover, the number of those species detected in eDNA tended to be maintained at a greater distance from the fishpond where they originated, compared to eRNA. Therefore, we conclude that environmental RNA is useful for fish ecosystem surveys in bays contaminated by fish feed because of the lower content of RNA in the samples compared to DNA and because it is less easily detected and diffused in the environment.