This is just something that happens from time to time. For example, it happened in February of this year (prior to the release of treated water from Fukushima)

This is just something that happens from time to time. For example, it happened in February of this year (prior to the release of treated water from Fukushima) in Itoigawa [1]. While it's understandable that someone's mind would jump to Fukushima as a possible cause, since it's been in the news recently, it is likely just due to natural phenomena such as the fish being chased ashore by a pod of dolphins. [1] https://news.yahoo.co.jp/articles/a5e8d11585ad014f14b45ad0bfc20dd82a797462 https://news.yahoo.co.jp/articles/a5e8d11585ad014f14b45ad0bf...