The investigation concerned artificial reefs that are creating kelp, Laminaria lerigiosa, habitat at Biya, Hokkaido, Japan. Since the water on the shore side of reefs was shallow, the velocity of water particles due to waves was high, restraining feeding pressure from sea urchins, Strongylocentrotus nudus, and assisting in the formation of kelp forests. However, regarding the reefs on the open sea, the water was deep and wave velocity was low, resulting in intensive feeding pressure from sea urchins and subsequent barren ground. Sea urchins on reefs at the shore side grow faster than ones at the open sea. By adjusting the water depth using rocks and blocks, wave velocity could restrain feeding pressure from sea urchins, thus making it possible to create kelp forests for the fishery of sea urchin.
