ABSTRACT
Japan has a long history of intensively working to increase its food production from the sea. The continental shelf around Japan occupies an area of 242,000 km. There are plans for developing 5 percent of this area into mariculture grounds. This is expected to increase the annual output of marine fisheries products by 4.8 million tons, which is about half of the current Japanese fisheries production. The fact that the projects are still funded probably rests less on biological and economic data than on the political situation which has resulted from the worldwide introduction of 200 mile fishing zones. Placing rocks in areas of soft sediments is one of the oldest and simplest enhancement techniques. It can be very effective, and Japanese fishermen have long engaged in transporting and placing rocks without the added incentive of government subsidies. Where the local fishermen use nets, they may select structures having smooth surfaces.
