Ichthyofaunal Composition, Distribution Patterns and Abundance in the Baralia River of Bodoland Territorial Region, Assam

Background: The Baralia River, an important north bank tributary of the Brahmaputra River, originates from Bherberi Bhumuk in Tamulpur district and remains insufficiently explored with respect to ichthyofaunal diversity and ecological status. Objectives: To evaluate fish diversity, distribution patterns, and their relationship with physico-chemical parameters across different seasons and sampling sites of the Baralia River. Materials and Methods: Fish samples were collected from five sampling sites during different seasons. Species composition, abundance, diversity indices, spatial clustering, conservation status, and correlations with physico-chemical parameters were analyzed. Results: A total of 9,607 individuals belonging to 61 species, 46 genera, 22 families, and eight orders were recorded. Oreochromis mossambicus was the only exotic species observed. Cypriniformes was the dominant order (52.46%), followed by Siluriformes (21.31%) and Anabantiformes (13.11%). At the family level, Cyprinidae (26.23%) and Danionidae (16.39%) showed highest species richness, while Danionidae (32.96%) and Cyprinidae (30.16%) together contributed 63.12% of total abundance. Seasonal variation indicated dominance of Danionidae during premonsoon, monsoon, and winter, whereas Cyprinidae dominated during retreating monsoon. Cluster analysis revealed distinct spatial heterogeneity, with upstream sites (S1 and S2) differing markedly from midstream and downstream sites (S3-S5). Diversity indices showed high species diversity and evenness, peaking during the monsoon season. According to the International Union for Conservation of Nature Red List (2026), 88.52% of species were Least Concern, while 4.92% were Vulnerable, 3.28% Near Threatened, and 3.28% Endangered. Dissolved oxygen (7.06-11.56 mg l⁻¹) showed strong positive correlation with species richness (r=0.864) and abundance (r=0.745), whereas water temperature, total dissolved solids, electrical conductivity, free CO₂, and nitrate were negatively correlated. Conclusion: The Baralia River supports rich freshwater fish diversity and exhibits significant ecological value. Immediate conservation and management strategies are necessary to safeguard its ichthyofaunal resources and maintain ecosystem health.