Shrimp Farming and the Environment - Library

• Supply and effluent canals should be isolated as far as possible from each other, and fromother farms.In practice, the last of these will be difficult to achieve in the absence of a broader planning framework,including water supply/disposal infrastructure.In all cases of new farm construction or existing farm rehabilitation, farms should be designed andengineered to allow other economic activities to surface should there be shrimp crop failures, as hashappened over the last decade or more in all of the major shrimp-producing countries. This is aparticularly important issue in poor coastal communities, whose residents derive their livelihoods fromcoastal aquaculture. If an operation fails, a plan and the infrastructure should exist for the culture ofother species, which often will usually have a much lower market price. If this is not possible, a“fallow” period may be planned to allow recovery of soil quality and decline of disease organisms, asis commonly practiced in agriculture. Thus, investment in the farm should be based on the assumptionthat culture of lower-value species, or a fallow period, would follow failed shrimp culture, and thateven with repayment of the amortized investment, the profitability of the farm would remainsufficiently high to justify continued operation. Sustainable seed supply and nutritional needs should beconsidered in the selection of alternate species so as to reduce their overall impacts.Technology and researchImproved technology should allow for significant reductions in the environmental impact of shrimpfarming. In particular:• Increased supply of seed from hatcheries and breeding of pond-reared shrimp should reducethe potential risk of depleting wild stocks and allow for greater control of disease;• Breeding may also produce disease-resistant strains;• Adoption of semiclosed, closed, and recycled systems should reduce environmental impacts—if well designed and managed;• New technologies for water treatment and management should improve pond water andeffluent quality;• Lining of ponds or dikes may reduce seepage and, in some cases, saline contamination;• Techniques for identifying disease in broodstock and seed, and for the early identification ofdisease in ponds, should reduce disease incidence and allow for more effective treatments;• Development and adoption of low-fishmeal diets should protect shrimp farmers from thelikely rise in prices of fishmeal in the future, as well as reducing pressure from aquaculture onthese prices; and• Development of higher-quality, low-pollution diets will reduce feed-associated wastes in pondwater and thus improve effluent quality.Promoting these developments in technology will require collaboration between government, shrimpfarmers, and feed manufacturers. Some changes in technology may be advanced through a set ofincentives and constraints, which might include regulation, taxation, grants, and marketing schemes.These are discussed further in Chapter 6.ManagementPoor management is a major contributing factor to the environmental effects of shrimp farming.Relatively simple changes in management practices can lead to significant reductions in environmentalimpact:• Careful management of soil, in particular soil acidity, through appropriate treatment includingregular flushing, liming, or lining with laterite soils, may improve pond water quality andreduce shrimp stress and disease;• Treatment of influent water supply (for example with chlorine) to eliminate pathogens andcarriers may reduce disease incidence and associated use of chemicals;• Skilled assessment of seed health prior to purchase should reduce disease risks;• Modest stocking rates—combined with knowledge, skills, and technology—should reduce therisk and severity of losses from disease;37