A Reevaluation of Extensive Aquaculture Systems in Madura Island, East Java, Indonesia

1) A survey of aquaculture systems in Madura Island, East Java, Indonesia, was conducted during the summer of 1981. The systems were reevaluated from the viewpoint of aquaculture physiology and were compared with other systems in world aquaculture.2) According to fishery statistics, annual yield of aquaculture from 1976 to 1979 had an average of 163,740 tons. Distribution rate of this yield among the total fisheries products was calculated to be 19.4% in weight and 48.5% in prices, whereas in Kagoshima Prefecture the rates were 12.2% and 31.3%, respectively. These features show that aquaculture in East Java has continuously played an important role in the fisheries industry.3) Most aquaculture techniques in Madura Island were based on the utilization of the natural sources from the land and coastal waters. Several types of mangroves serve as sources of pond nutrients from decaying leaves and their seeds. Fish larvae and planktonic diets were naturally supplied by tidal current. Predators such as crabs were trapped daily and were utilized for family and local consumption. Supplemental feeds and fertilizers were not supplied into the pond.4) The fish ponds were constructed by digging and concaving the catchment basins. Dugged soil are then used for dike construction. The size of the ponds was generally 0.5~1.0 ha including the "halfway island" at the center of the pond. The halfway islands were submerged in water during high tides, and were exposed to the air at low tides. Mangrove trees also serve as protection of dikes from erosion and sanctuaries or "resting" area of cultured fish.5) In Southeast Asia, the average yield of fish in ponds vary greatly from 245 kg・ha^<-1> in Java, 694 kg・ha^<-1> in Philippines, to as high as 2,067 kg・ha^<-1> in Taiwan. The yield in Madura Island, however, was estimated only at 100~120 kg・ha^<-1>. Such variation may be due to differences in culture methods adopted. In Taiwan, intensive feeding using artificial diets is done. Supplemental feeding and pond fertilization are also being applied in the Philippines. In the west coast of Madura Island, however, neither fertilization nor supplemental feeding is employed