Fish fauna in damaged rivers by heavy rainfall in Northern Kyushu District, Japan in July 2017

The purpose of this research is to describe and evaluate an example of the impact of large-scale disasters on a fish fauna of rivers. In the northern part of Kyushu from July 5th to 6th, 2017, a heavy rain fell steeply into a specific area Especially in Asakura city, Fukuoka, Japan there was a recordable heavy rain which resulted in major damage to roads, buildings and rivers. From July to December 2017, we conducted capture survey at eight sites and environmental DNA (eDNA) metabarcoding at 18 sites in the middle reach tributaries of right bank of Chikugo River system in Kyushu, Japan. In the capture survey, four species 470 individuals were found from eight sites, although fish were not captured at three of those sites. In an eDNA analysis, 21 species were detected from 18 sites, however fish eDNA was not amplified at seven of those sites. The fish fauna of capture survey and eDNA analysis coincided at seven out of eight sites, which showed the high accuracy of fish fauna detection by eDNA analysis in this study. Our result confirmed that this heavy rainfall devastated blow to the fish fauna of the rivers.