The source of the river is in the city of Mihara, Hiroshima and flows generally east toward Niimi, Okayama.

The Ashida River originates in Daiwa-chō, Mihara on the Sera Plateau in Hiroshima Prefecture in Japan.

[2] Flood retaining walls were constructed along the banks of the Ashida River in 1928.

The Japanese Ministry of the Environment had designated the species as extremely endangered.

Environmental DNA analysis was utilized by the university to determine the concentration of the bitterling fish in various portions of the river.