Shrimp Farming and the Environment - Library

• Reductions in water exchange coupled with increased aeration and careful pond watermanagement can reduce the quantity of routine effluents, and may reduce the rate of diseasespread;• Intensive aeration may itself serve as a form of water treatment;• Careful management of water at the time of harvest, and effective use of settling ponds, cangreatly reduce nutrient and organic matter loadings on the environment;• Careful disposal of pond sediments (rather than simple flushing) to allow for oxidation anddecomposition will greatly reduce the nutrient and organic matter loading to the environment;• Providing the right amount of high-quality food at the right time throughout the productioncycle can greatly reduce feed and metabolic wastes;• High-quality husbandry, knowledge and skills in identifying and treating disease will greatlyreduce the incidence of disease and the associated use of chemicals; and• Observance of an adequate withdrawal period when chemicals and therapeutants have to beused, to clear the shrimp of residues, will improve their marketability and raise their marketvalue.ImplementationThe implementation of these varied approaches to reducing environmental impact and promotingsustainability will depend upon managers and staff having adequate skills and access to information,and in many cases some form of government—or market-initiated incentives or constraints.Furthermore, some of the mitigation measures (for example, restrictions on siting, provision ofinfrastructure, or development of disease prevention and management strategies) will require directgovernment intervention. The key roles for central and local government in facilitating, promoting, andin some cases directly implementing these mitigation measures is discussed in Chapter 6.Further discussion and detailed guidelines for measures to reduce the environmental impact of shrimpfarming can be found in several recent publications (Barg 1992; SEACAM 1999; Hambrey 1996c;Pillay 1997; Clay 1996; Global Aquaculture Alliance 1998; GESAMP 1999; Institute of Aquaculture1996).38