| A coralline flats to which the seaweed beds disappears are widely distributed in the sea area. The seaweed beds are important as fishes’ spawning ground and living places. The coast structures to make the algae place (the rear step of breakwater) have been constructed in Hokkaido JAPAN. [*] However、 the decrease in the effect of algae place creation is feared by the aged deterioration of the substrate and the elevated water temperature in recent years. It is required to devise the measures against disappearance of the seaweed colony. Field investigation concerning distribution of seaweed beds and physical environment was performed in fishing port of Hokkaido from 2007 to 2010.[*] In this study、 the results of the field investigation are introduced. It is found that one of the causes is feeding pressure to seaweed of sea urchin. It is strongly dependent on water temperature in winter. To control feeding the seaweed、 it is necessary to improve flow velocity on the rear step of breakwater more. |
