Ecology and Partial Restoration of Daha River for Fish Productivity

Daha river, a threatened water body of polluted nature in the Gopalganj district of Bihar was studied for its degradation and possible restoration. The study reveals high rate of sedimentation and agricultural activities, changes in water quality and biotic community. Agricultural activities have led to high input of nitrogen (N) and phosphate (P) fertilizers along with pesticides being used by the farmers. The positives response of restoration practices was observed with partial improvement in fish-productivity due to hindrance factors acting upon severe fish species.The mean concentration of phosphate, nitrate and ammonia corresponds about 0.60-1.40 mg/l, 1.30-2.50 mg/l and 23-43 mg/l in polluted river, while after restoration declines to 0.20-0.48 mg/l, 0.60-1.10 mg/l and 14-27 mg/l, respectively indicating more suitable towards fish productivity. The observations on other water parameters also showed similar trend during partial restoration of Daha river. The cause of algal bloom and other macrophytic population is inorganic ammonia, however, organic pollution is also in polluted state observed as more quantity of ammonia than nitrate especially at site II and Site III during the study period. The concentration of nitrate is much higher than the critical value in polluted river which causes algal diversity and macrophytic vegetation. Therefore, partial restoration of the river helped to enhance fish productivity concluded from this study.