Predictive Modeling of a Fish-Based Index of Biotic Integrity in Assessing Environmental Degradation in the Lower Teesta River Basin of Eastern Himalayan Foothills, India

River Teesta is experiencing huge anthropogenic interventions at several levels. This fact augmented an urgent need for the assessment of the riverine environment. In the present study, the lower Teesta River basin is selected following the intensified damming activity and increasing human footprint. Seven sampling sites were chosen upon which a fish-based index of biotic integrity is developed. Three sampling sites viz. Rungpo, Rishikhola, and Gajoldoba have an “Acceptable” status. The number of lithophilic spawners and the percentage of carnivores drove the maximal variation among the sampling sites. Physical habitat characteristics and riparian influences were incorporated into a generalized model to predict the fish-based index of biotic integrity spatially. An “Acceptable” status is predicted along the upper stretch of the lower Teesta River basin. In contrast, the “Impaired” status is foretold along the plains. Also, the stream water index strongly correlates with the developed fish-based index of biotic integrity index, affirming adequate demonstration of ecological conditions. © 2023, Zoological Society, Kolkata, India.