FISH is the cheaper and main source of dietary protein for the nearly 150 million people of Bangladesh and will be depended upon in the diet for all aspects of nutrition by an even bigger population in the future. But this source of nutrition is already under a threat due to dwindling reproduction of various species of sweet water fishes. Bangladesh in the past was home to four or five hundred species of fishes. The number has dwindled down to two hundred and fifty such species with the others becoming extinct. But even the supplies of the species which are still seen, appear to be fast shrinking. The main reason for the extinction as well as dwindling supplies, is the spread into water bodies of chemical substances such as pesticides and insecticides used in agriculture. According to a newspaper report, nearly thousands of tonnes of such chemicals are used in agricultural lands and nearly 50 per cent of the same pass into water bodies. The chemicals are poisonous for the fish and the environment. The situation calls for immediate stringent regulations so that the same can be prevented from passing into water bodies which are the natural breeding and feeding grounds of fishes. In many countries, farmers are practicing the safer natural ways of pest control without using insecticides and pesticides. The same should be encouraged in Bangladesh. At least, the use of chemical insecticides and pesticides should be regulated severely. The laws and their enforcement should be strictly ensured. Besides, enforcement of law related to fish catching, and punishing of those netting fish fries and posing hazards to the water bodies, will have to be stepped up with a greater zeal. All adverse interferences in the free and healthful breeding of fishes in their natural habitats must be stopped.