抄録
Communities of algae have disappeared from the shallow waters along the Japan Sea coastline in southwest Hokkaido. A large number of studies have been made on coralline flats, it has been shown that the consumption of algae by sea urchins is an important factor affecting the formation of coralline flats, and is closely related to the physical environment of coastal areas. Field investigations have shown that sea urchin moves to offshore avoiding strong fluid velocity when waves are big, on the contrary it moves to onshore in order to eat algae when waves are small. On-offshore movement of sea urchin due to waves are not quantitatively studied. Movement of sea urchin to offshore due to increasing of wave height, and these to onshore due to decreasing of wave height are experimentally understood. Decrease of sea urchin velocity under large fluid velocity are quantitatively investigated.
