Contents

ABSTRACT

Brackishwater aquaculture is a relatively new and rapidly expanding practice, centered in South and Southeast Asia, but also growing in Latin America and just getting underway in Africa. In terms of total fish landings for the world, its contribution is minor at present, but with the stimulus of the very high international market value of penaeid shrimp, new pond area is being rapidly added in many tropical and sub-tropical countries and old coastal pond areas are being renovated. Often this expansion is occurring with the loss of mangrove forest and in soils and sediments which are far from ideal for aquaculture. In these soils the presence of massive quantities of pyrite will leach sulfuric acid and metals at highly toxic concentrations into culture ponds for periods of years to decades following construction. Although there are a number of methods to build ponds which could minimize the acidity problems and management practices which can reduce the scale of the negative impacts through accelerated leaching of acidity and neutralization with lime, these practices have not been generally employed up to now. As expansion in pond area is occurring in acid sulfate soils without appreciation of the scale of difficulties that acidity leaching will impose, it appears likely that considerable loss of public and private capital will occur in a significant proportion of the projects for which high yields of high value culture organisms are necessary to repay the initial investments. In addition, loss of appreciable areas of mangrove forest to low productivity aquaculture ponds could erode the natural capacity of the coastal zone fisheries and thus lead to a net economic loss and social problems.