The impact of pollution to seafarming is immeasurable short and long term damages to the environment and the cultured stocks. In assessment of potential site for the seafarming development, the impact of pollution is considered to ensure that the investment would not be unduly affected by the adverse effect of pollutants. In these considerations, the located pollutant sources and the pattern of seawater transport are carefully considered.
The domestic sewage is a source of detergents, stable and unstable nutrients, solids, various toxic substance and pathogens causing health hazard to varying degree. Discharge of untreated domestic sewage resulting in high organic loads to rivers, canals, bay and indented coastlines have been known to cause eutrophication, and highly prolific disease infection of finfish and molluscs.
Agricultural pollution problems are equally serious typically involving animal wastes, solids, insecticides, herbicides. The agricultural pollution can cause adverse effects to seafarming. At present the effect is not too serious in coastal zone, but there were cases causing an epidemic of disease among of fish in freshwater ponds and open waters. The phenomena in late 1980 was suspected that pesticides might have been involved as a contributory factors
Industrial activities offer a diverse variety of pollution. In area where the effluents are not treated before discharge as in many developing countries, the siting of culture farms in the proximity of industrial activities is most unwise.
Range and complexity of water pollution from industrial wastes have increased, particularly from the development of the electronic and electro-plating industries. Other sources include tanneries, textile mills, food processing, distilleries, chlor-alkali plants, rubber products and chemical works. These industrial wastes can cause high level of heavy metals accumulated in molluscs.
Fish kills have been observed from time to time in several rivers, including the Musi River in Sumatra where there is a large fertilizer plant periodically discharging urea and ammonia. Arsenic compounds, phenols and chlorinated phenols are used in timber preservation are suspected of causing adverse effects in the Kalkapa River, Kalimantan.
Types of industry and its potential chemical wastes that may contaminate the environment is given in Table 12. The level of the industrial wastes that may endanger the life of fish especially those kept in confinement, and molluscs is presented in Table 13.
The discharge of human wastes in untreated forms into rivers, canals, and bay can spread many of the common tropical diseases such as cholera, typhoid, hepatitides, etc. In area that have molluscs culture, if the virus and bacterial pathogen are present in the surrounding water, they may accumulate into tissues of the molluscs. It can pose a health hazard to the consumers, if the level is beyond the acceptable level.
To avoid such hazard or reduce chance to be damaged by pollution of different sources, it is thus essential to select the site for seafarming operation away from the pollutants sources as much as possible. The potential sources of pollutants in different provinces are listed in Table 14
