‘I’ve never seen anything like this’: Japan says reason behind 1,200 tonnes of fish washing ashore is unknown

Sardines and mackerels are seen washed up on a beach in Hakodate, Hokkaido, northern Japan. Photograph: 瀬尾遊/AP

Officials in Japan have admitted they are struggling to determine why hundreds of tonnes of fish have washed ashore in recent days.

Earlier this month, an estimated 1,200 tonnes of sardines and mackerel were found floating on the surface of the sea off the fishing port of Hakodate in Hokkaido, forming a silver blanket stretching for more than a kilometre.