Shrimp Farming and the Environment - Library

• Farm-level management; and• Industry-level management.Recommendations for each of these are summarized on the following pages.Site selectionSite selection is of great importance, not only for ensuring appropriate soil and water regimes for thefarm, but also because of broader issues such as the proximity of other farms and the carrying capacityof the environment. If carrying capacity is exceeded and water quality and ecological degradationensue, this will affect both shrimp farmers and other users.Appropriate siting of shrimp farming can help:• Minimize critical natural habitat destruction;• Minimize destruction of, or adverse effects on, otherwise productive land;• Minimize the impacts of shrimp farm effluents (for example, by siting adjacent to areas withhigh assimilative capacity—such as mangrove or well-flushed coastline);• Minimize the spread of disease (by maintaining adequate separation between farms andadequate separation between influent and effluent waters);• Prevent saline contamination of groundwater, agricultural land, and freshwater irrigationsystems—which can result from withdrawal, discharge, or seepage; and• Maximize the productivity of shrimp farming itself (by siting on suitable soils and in locationswith access to high-quality water supply).While rational site selection may be possible—and is indeed an essential part of project planning andfeasibility studies for large shrimp farming projects—smaller and poor farmers generally choose siteson the basis of availability rather than suitability. Some form of government intervention may thereforebe required to restrain development in unsuitable areas and/or to facilitate development in suitableareas. If the issues discussed above are to be fully addressed, this will require a comprehensiveassessment of natural resources and land use potential, leading to land use planning policies, possiblyincorporating zoning, and implemented through a set of powerful incentives and constraints.Extent of shrimp farmingImpacts on the natural environment may be reduced by limiting the area that shrimp farming canoccupy. If the objective is to maximize production with minimal habitat destruction or land useconversion, then the intensification of existing farms rather than the development of new farms may bean appropriate strategy (Hambrey 1996b; Menasveta 1997), if the other potential problems associatedwith more intensive systems can be addressed. Where shrimp production is seasonal, total productionper unit area may be increased by growing an alternative crop in the less suitable season (e.g., rice,finfish, Macrobrachium, Artemia, or salt depending on local circumstances).DesignGood design of shrimp ponds—in particular, design of water supply and discharge systems—can havea major impact on sustainability. Good design can:• Ensure high-quality water supply and optimal pond water conditions;• Reduce the likelihood of disease and the use of undesirable chemicals;• Minimize effluent quantity and/or maximize effluent quality; and• Prevent salinization of adjacent agricultural lands, groundwater, or freshwater irrigationsystems.Principles of pond design can be found in many standard texts (Fast & Lester 1992). However, tominimize the environmental impact of semi-intensive and intensive shrimp farming, the followingprinciples should be adhered to wherever feasible:• Settling ponds suitable for both routine and harvest effluents should be constructed;• Reservoirs for water storage and treatment should be included; and36