Shrimp Farming and the Environment - Library

CHAPTER 3: ENVIRONMENTAL IMPACTS OF SHRIMPAQUACULTUREFor centuries, the coastline has been the most important human habitat, and, as a result, has beensubject to a wide range of development pressures. Shrimp farming represents additional pressure onthese areas, at least potentially. While shrimp farming per se does not necessarily have a significantadverse impact on the coastal environment, inappropriate practices and unplanned development haveled to a number of problems.The main environmental impacts associated with shrimp aquaculture, and ways in which specificimpacts can be reduced or mitigated, are discussed below. The means by which these mitigatingmeasures can be facilitated, promoted, or enforced at the farm level are discussed further in Chapter 7,but these vary greatly according to the particular kind of shrimp farming, the socioeconomic status ofthe farmers, and other local circumstances. More detailed guidance will be developed in Phase II of thisstudy.The actual or potential environmental impacts of shrimp farming fall into the following categories:• Destruction of natural habitat (through direct conversion);• Abstraction/contamination and salinization of groundwater;• Organic matter and nutrient pollution;• Chemicals;• Disease;• Harvest of broodstock and wild post-larvae (PL);• Introduction of exotic species;• Abandonment; and• Use of fishmeal in feeds.The emphasis of this report is on ways to make shrimp farming more sustainable. As a result, theemphasis of this chapter is on mitigation measures to address negative impacts. In some instances, suchmeasures have already been adopted widely by the industry; in others, the suggestions are based moreon theory than on practical application. In either case, more research needs to be undertaken todocument the effectiveness of the proposed mitigation measures in addressing the impacts.From the outset, however, it should be emphasized that many of the impacts from shrimp aquacultureare not unique to that industry. Rather, they are typical of agricultural practices in general, especiallywhere land is in short supply. It should also be noted that shrimp farms suffer a great deal frompollution caused by other activities, including agriculture and industry. Indeed, while many otheractivities are relatively careless of their environment, experienced shrimp farmers realize that long-termbenefits result from maintaining environmental quality. When establishing new farms, water quality isone of the most important factors to consider; sites where industry, agriculture, or other activities arepolluting the water should be avoided.Destruction of natural habitatExtensive shrimp farming takes place in the intertidal zone, commonly in or adjacent to estuarinesystems. Semi-intensive and intensive shrimp farming usually takes place in the upper intertidal or justbehind/above the intertidal zone, often in adjacent wetlands. Some shrimp farming now takes place ininland areas. Most tropical estuarine systems are dominated by mangrove, an intertidal ecosystem oftree and shrub species specially adapted to saline habitats, that support a wide range of otherorganisms.In the early part of the 20th century, many estuarine systems and wetlands remained relatively freefrom development because of their unsuitability for agriculture and the costs of clearance and drainagefor urban development. In the 1960s, ’70s, and ’80s, they were regarded as wasteland by many, andgovernments and international agencies actively encouraged private sector development foraquaculture and other enterprises. It is only relatively recently that their biodiversity and ecologicalvalue has been widely recognized. It should be emphasized that while the most attention has been paidto mangrove in recent years, estuarine systems in general, including salt flats, mud flats, lagoons,20