Understanding the habitat status of fishes in the upper reaches of the Nogawa River , Tokyo: Combining sampling surveys and environmental DNA surveys.

Abstract

We revealed the habitat status of the fishes in the upper reaches of the Nogawa River in Tokyo using environmental DNA surveys and sampling surveys. These fishes consisted mainly of those living in the river's middle reaches. In environmental DNA analysis, Opsariichthys platypus, Pseudorasbora parva, and Gnathopogon elongatus showed high read counts. It was also found that some confirmed fish species were endangered and non-native species. The results of the two surveys suggested that the environmental DNA survey could complement the sampling survey. Through these surveys and results, we organized and compared the characteristics of both surveys. The environmental DNA survey and sampling survey were found to have advantages and disadvantages in the "sample collection" and "analysis" stages. The biological monitoring survey considered that using both surveys could provide a more accurate picture of inhabiting fishes and invasive alien species invasions. For resource management, ecosystem management, and conservation, more efficient and accurate results will be obtained by combining multiple survey and analysis methods and considering detailed condition settings, depending on the objectives.