50. Pesticides and Environmental Pollution - Toxicogenic Effects on Fishes

All living organisms incuding man have been exposed to certain types of toxic substances since time immemorial. Advances in Science and Technology have provided to mankind capabilities and know-how to produce synthetic chemicals some of which are highly toxic but their precise effect on the life processes still remain inadequately known. Toxic chemicals invariably find their way into the body tissue directly or indirectly through complex food chain and some of these are quite stable or have unusually long half-life. Further, certain toxic chemicals are neither fully metabolized nor quickly detoxicated and, therefore, create serious problems or residue accumulation. The synthetic pesticides fall in this category. The pesticides have become a necessary evil. Indiscriminate use of pesticides, careless handling, accidental spillage, or discharge of untreated effluents into natural waterways have harmful effects on the fish population and other aquatic biotopes. The indiscriminate use of pesticides can be considered one of the factors which changes the environment causing several imbalances in the ecosystem, especially the denizens of the aquatic environment. Over use of pesticides may not include disturbance and disequillibrium in aquatic and terrestrial environment, but it may hae adverse effects on nontarget organisms such as fish and other aquatic invertebrates. Yet, the pesticides are considered indispensable for pest control in agricultural production, animal husbandry and public health programmes. However, continued and attimes excessive and unplanned use of pesticides has resulted in high level of environmental pollution, residues and even problems of toxic diseases, morbidity and mortality. There is need to understand the various aspects of pollution and environmental threats to aquatic species. Management strategies are needed for protection and conservation of our aquatic resources.