The sardines and some mackerel washed ashore in Hakodate on Japan’s northernmost main island of Hokkaido on Thursday morning, creating a sliver blanket along a stretch of beach about a kilometer (0.6 mile) long. Takashi Fujioka, a Hakodate Fisheries Research Institute said the fish may have been chased by larger fish, become exhausted due to a lack of oxygen while moving in a densely packed school, and were washed up by the waves.