Integration of aquaculture and mangroves

Abstract

Southeast Asia has the highest concentration of mangroves and brackish water aquaculture ponds. This paper describes studies that integrate mangroves as biofilters, and as pen culture sites for mud crab farming. In one study, passing shrimp pond effluents through a natural mangrove stand reduced levels of TSS, sulfide, NH₃-N and NO₃-N by 18.7%–64.2%. Estimates show that 1.4–6.5 ha of mangroves are needed to assimilate nitrogen wastes from one hectare of shrimp pond. Mangrove biomass increase was 2.5 times greater with effluents compared to a control mangrove, although plant numbers remained similar. Present mud crab Scylla spp. farming still depends on raw (“trash”) fish and wild seed. To lessen such dependence, another study compared the stocking of hatchery vs wild juveniles, and feeding of pellet + raw fish (“trash fish”) vs fish alone. Preliminary results show that low-cost pellets can reduce raw fish requirement, and that hatchery crab juveniles need immediate feeding whereas wild crabs can subsist on natural mangrove productivity for one month. Mud crab pen culture is commercially viable but technological refinements and land tenure issues remain.