Hundreds of tonnes of fish have washed ashore in Japan, triggering a comprehensive investigation by authorities. The incident has left officials baffled and local communities concerned about potential environmental and economic repercussions.

In Hakodate, Hokkaido, approximately 1,200 tonnes of sardines and mackerel formed a surreal silver blanket on the sea’s surface, extending for over a kilometre.

Shortly afterwards, Nakiri, a town on the Pacific coast, also experienced a similar and unexpected fish wash-up, with 30 to 40 tonnes of Japanese-scaled sardines littering its shores. Concerned officials and local fishers hastily collected the stranded fish to prevent potential environmental damage caused by decomposing carcasses lowering water oxygen levels.

A fisherman with 25 years of experience in the area expressed his astonishment, stating, “I’ve never seen anything like this before,” sparking concerns about potential changes in the marine ecosystem.

Experts suggest that migratory fish in both areas may have become stranded due to exhaustion from being pursued by predatory fish like amberjack. Sudden drops in water temperature could also lead to mass mortality events.

Despite these speculations, the exact cause remains unconfirmed, and local officials plan to sample seawater at the site to conduct further examinations.

Criticism emerged when global media linked the phenomenon to the release of treated water from the Fukushima Daiichi nuclear power plant. Japanese government officials swiftly dismissed the report, asserting that the cause remains unknown.

Dead fish started washing ashore approximately four months after the Fukushima Daiichi nuclear power plant began discharging water into the Pacific. The discharged water contains small quantities of the radioactive isotope tritium. The International Atomic Energy Agency (IAEA) approved the discharge plan, claiming it would have a negligible radiological impact after conducting a safety review.

China opposed the release and imposed a ban on Japanese seafood, leading to accusations of hypocrisy as China’s nuclear plants discharge wastewater with higher tritium levels than Fukushima’s discharge.

Japanese fisheries agency officials expressed concern about unsubstantiated information and emphasized the need for accurate information dissemination. Images of the fish washing ashore have circulated widely on social media, often accompanied by conspiracy theories related to Fukushima.

The fisheries agency stated that water-monitoring surveys have not shown any abnormalities in the discharged water from the Fukushima plant, emphasizing the importance of relying on scientific evidence for information.

Fishing cooperatives in Fukushima expressed concerns that the discharge would harm the reputation of their seafood, highlighting the economic impact on local fisheries. Town officials in Hakodate advised against consuming the stranded fish, and there were reports of people gathering them for sale or consumption.

A fisheries researcher, Takashi Fujioka, stated that the circumstances under which the fish washed ashore are unknown; therefore, eating them is not recommended.