Assessment of fish habitat suitability in the wake of elevated pollution of a tropical river in India.

Evaluating fish habitat suitability (FHS) is of utmost importance in the present times, as rising pollution and ecological stress have led to the deterioration of their habitat and population. The present study has evaluated ecological water quality using the comprehensive pollution index (CPI), eutrophication index (EI), and organic pollution index (OPI). Fish community structure has been assessed based on tropic level score (TLC) and habitat orientation score (HOS). Moreover, FHS has been evaluated using the habitat suitability index (HSI). These assessments have been conducted in the spatio-temporal dimension. This study demonstrates that the ecological water quality is significantly poorer during the monsoon (MON) season, according to the CPI. However, it was at its lowest during the pre-monson (PRM) season in 2014-2015 and the post-monson (POM) season in 2022-2023, as indicated by the OPI and EI. The water is significantly polluted downstream of the Durgapur barrage, particularly after the Tamla Nallah confluence. According to the CPI, 72.73% of water samples during the MON season were highly contaminated in 2014-2015 and in 2022-2023. Practically water was badly polluted in all seasons according to the OPI and EI. The fish community composition indicates that the river is currently in a precarious state, and the ecosystems inside the river have undergone alterations in certain areas. According to the HSI, the Damodar River exhibits diminishing appropriateness for fish habitat during PRM season in certain areas, while other seasons show no suitability for fish habitat. This investigation will be highly beneficial for mitigating pollution and restoring rivers. It is crucial to uphold and conserve freshwater biodiversity and the ecosystem services provided by the river.