Influence of Physicochemical Water Quality Variables on Ichthyofaunal Diversity in the Hasdeo River and Its Tributaries (Ahiran, Tan, and Chornai Rivers), District Korba, Chhattisgarh, India

Freshwater fish communities are strongly influenced by spatial and seasonal variations in water quality, particularly in river basins exposed to anthropogenic pressures. This study evaluated the influence of physicochemical water-quality variables on ichthyofaunal diversity in the Hasdeo River and its tributaries - Ahiran, Tan, and Chornai in Korba District, Chhattisgarh, India. Sampling was conducted at 12 stations from May 2025 to April 2026 across pre-monsoon, monsoon, and post-monsoon seasons, generating 36 observations. Water temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS) were assessed alongside species richness, Shannon diversity, Simpson dominance, and Pielou evenness. Data were analysed using one-way and two-way ANOVA, Tukey’s HSD test, Pearson correlation, and heat-map visualization. Hasdeo recorded the highest species richness (45.11 ± 3.22), Shannon diversity (3.61 ± 0.10), and Pielou evenness (0.95 ± 0.01), whereas Chornai showed the lowest richness (28.22 ± 2.28) and Shannon diversity (2.88 ± 0.10) and the highest Simpson dominance (0.14 ± 0.01). One-way ANOVA revealed significant river-wise differences in all fish-diversity indices, pH, BOD, COD, and TDS. Two-way ANOVA showed significant main effects of river and season on the biological and physicochemical variables, while River × Season interactions were non-significant for all fish-diversity indices and significant only for selected physicochemical variables. DO was positively correlated with species richness (r = 0.487), Shannon diversity (r = 0.479), and evenness (r = 0.428), whereas BOD and COD showed strong negative associations with richness and Shannon diversity. Overall, fish-diversity patterns broadly followed Hasdeo > Ahiran > Tan > Chornai, emphasizing the importance of regular monitoring and pollution-control measures, particularly in the Tan and Chornai rivers.