The most diverse ecosystem in the world is the aquatic ecosystem, but in recent times, water pollution is one of the prime ecological concerns, disturbing the natural habitat of aquatic lives. The effluents from Hindustan Paper Co. Ltd., Panchgram are highly toxic and a major source of contamination of Barak River. Fish serves as bioindicators of environmental contamination and therefore be used for assessing the quality of the aquatic ecosystem. Thus, the present study focused on investigating the effects of Paper Mill effluents on Anabas testudineus. Water samples were collected from three different sites, i.e., upstream, on-site and downstream of effluent discharge site in Barak river. Collected water samples were diluted in the ratio 1:4 with distilled water and fishes of similar size and weight were exposed. Fish weight, swimming pattern, ocular movement, activeness and skin texture were observed for ten days. Hematological parameters of all the fishes were also studied on day 10. Fishes exposed to different water sample exhibited a variety of physiological responses. Fishes treated with on-site effluent water showed abnormal swimming pattern, dizziness, late response, high ocular movement along with corrosion of scales. The upstream water samples favoured fish growth and showed no sign of abnormalities. However, the paper mill effluents gradually diluted as it flows downstream and a lesser degree of abnormalities in fishes were observed as compared to on-site water. The evaluation of hematological parameters revealed the increased amount of WBC in on-site effluent water. Reduction in RBC count was observed in on-site contaminated water, whereas downstream water showed a marginal decrease in RBC count. Fish exposed to upstream water showed no anomalies in their hematological indices. Thus, the study concludes that the effluent discharge site of Barak River is not suitable for fish growth and survival. Moreover, long term effect may reach the extent of the threat, that can dwindle fish species in river Barak.
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