Nutrient budgets in intensive shrimp ponds: implications for sustainability

Serious production losses have occurred in shrimp producing countries around the world, principally due to poor rearing environments and pathogenic disease. In response to this, shrimp farmers are changing their culture methods. To understand the source and sink of nutrients which affect pondwater quality and effluent impact, the nitrogen, phosphorus and solids budget have been constructed for water exchange systems. These budgets reveal the contribution of the pond bottom soil to the accumulation of sediment and phosphorus and its potential contribution of nitrogen to the pond system. A survey of shrimp farm water quality and management practices in southern Thailand has also been completed. This reveals a high proportion of farms using low water exchange methods of shrimp culture but without the ability to maintain suitable water quality in the production ponds. Shrimp production in these systems is variable due to high incidences of disease and slow growth rates. The pond processes that might cause this are suggested and potential methods for their amelioration are discussed. Alternative culture systems such as lined ponds, low salinity rearing and recirculation farms are described in relation to their potential for remediating problems within the shrimp culture industry. (C) 1998 Elsevier Science B.V. All rights reserved.