Sustainable aquaculture in ponds: Principles, practices and limits

The global aquaculture production of crustaceans, shellfish and fish has to increase to satisfy the growing demand and also to compensate for the reduced capture from overexploited fisheries. Extending the area of brackish and fresh water ponds is constrained by the limited availability of land and fresh water. Oxygen availability limits productivity of non-aerated ponds to about 3500 kg/ha/year. In aquaculture ponds, a large fraction of input nutrients end up in the sediment while the harvested fish represents only a minor fraction of primary production. A higher fraction of the input nutrients should end up in harvested products, and ways to increase pond productivity per ha or per m3 that respect social, economic and environmental sustainability need to be explored. After reviewing the criteria for ecologically sustainable pond production, we discuss the financial and social factors under which sustainability can be reached by resource poor producers. Finally we review new technologies that will make future fresh and brackish water aquaculture systems more resource-efficient thus allowing the desired sustainable growth. Manipulating the Carbon:Nitrogen ratio of the water increases the production of both bio-flocs in the pond water and of bio-films on submerged surfaces. A further increase can be reached by increasing the submerged surfaces and by stocking the ponds with species using different niches in the aquatic food-web thus creating synergies. A global effort to optimize, integrate and disseminate such combined technologies may lead to a sustainable blue revolution in aquatic systems, similar to the green revolution for terrestrial crop production.