PRELIMINARY SIMPLE BIOLOGICAL TECHNIQUES FOR EXTENDING SURVIVAL DURATION OF FISH IN LETHAL MEDIUM OF DIFFERENT TYPES OF ENVIRONMENTAL POLLUTANTS - A REVIEWP.R. Balasubramanian and V. GopalAbstract Lethal effect of some of the industrial effluents, heavy metals. chemicals and pesticides on the fish Oreochromis mossambicus was evaluated by utilizing the median tolerance limit (um) or at which 50% of the test animals are killed (LC). Fish showed chronological response (chronological technique) to the same lethal concentration at different time of the day (light/dark cycle). Some of the industrial effluent tested, showed decrease in toxicity if stored in normal condition. Pre-extraction of pollutants in lethal medium with water hyacinth (biological technique) extended the survival duration of' the fish upto 480h - 72h). Water hyacinth, Eichhornia crassipes, showed an active phase of absorption around first 24h and after 48h with a lag phase between 24 and 48h. It was observed in many cases that pre-extraction period of 72h was beneficial which increased the survival of the fish in lethal medium to an extent of 113h to 480h in many pollutant studied. Hyacinth plant used in depollution studies may be used as a source for biogas production. The researcher's elsewhere has not been attempted to evaluate the similar kind of combined experiments (Pollutant - Lethal concentration, aquatic plants _ pre-extraction _ fish survival duration). For the purpose of the paper a review of work done in this laboratory was presented mainly on biological treatment technique.
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