Comparison of the Present Seaweed Bed Areas with the Estimated Areas in the 1950' along the Coast of Hyogo Prefecture, Eastern Seto Inland Sea

In the coastal areas of the Seto Inland Sea of Hyogo prefecture, seaweed beds have been declined in their density because of reclaiming due to drastic urbanization and industrialization after the high economic growth period in the 1950's in Japan. In order to estimate the area of seaweed beds in the 1950's, the following methods were adopted. Questionnaire survey was carried out in 23 fisheries departments and 72 fisheries cooperatives and then set the objected area from this result, and the range of present seaweed bed areas was obtained by using the topographical maps, charts, side scanning sonar, underwater video camera and transparency. As the results of our survey, total seaweed bed area in the 1950's was about 2300ha but about 920ha was disappeared by the reclaiming (430ha), bank protection work (140ha) and others (280ha). Good grasp for the transition of seaweed bed area in the past is very important issue to carried out the natural reproduction plan of seaweed bed area in future.