On March 6, a ‘kuki’ or large shoal of spawning herring was observed near the coast of Asari in the city of Otaru in central Hokkaido, turning approximately 3 km of the surface of the sea a milky white color.
　
The sea turns milky white when large numbers of male herrings release their sperm in time for the females to spawn. The waves stir up the water, causing white bubbles to float in some places. According to the Otaru Museum, the shoals were not seen in Otaru for a long time, due to poor herring catches, but have been seen every year since about 15 years ago. This year, they have been forming large shoals, including in areas around the coast, since February.
　
Herring are also known as the ‘fish that herald the coming of spring.’ “Herring have once again become a seasonal tradition. We can feel spring approaching in Otaru, too,” said the museum’s director. Otaru’s herring fishing season began on January 20 and will continue until early April.