Erratic Fish Behavior

Occurred on August 1, 2018 / Ibaraki, Japan

Info from Licensor: "This is a phenomenon I happened to encounter when working in Japan, in the Tonegawa River area. Can anyone explain this phenomenon? It is estimated to be around 2-3 thousand fish, approximately 10kg each. A few hundred tons. The Japanese people said they did not eat well. Like a mass suicide cult or something."