UTTAR PRADESH JOURNAL OF ZOOLOGY

The present study assessed freshwater fish and macroinvertebrate diversity in the Arlong Rup-at River and Era Kopili Wetland (locally known as a beel) in Karbi Anglong, Assam, India. Sampling was conducted from September 2024 to April 2025 at five river stations and two major wetland landing sites. Fish and macroinvertebrate specimens were collected using locally employed fishing gears and hand-based methods, photographed, preserved, identified using standard taxonomic literature, and evaluated using diversity indices and IUCN conservation categories. The Arlong Rup-at River yielded 35 fish species representing 7 orders, 16 families, and 26 genera, together with 4 macroinvertebrate species. Era Kopili Wetland yielded 38 fish species representing 10 orders, 18 families, and 29 genera, together with 6 macroinvertebrate species. The Shannon–Wiener index was higher in the river (2.103) than in the wetland (1.364), as were Margalef's richness (4.225 versus 1.934) and Pielou's evenness (0.758 versus 0.471). Menhinick's diversity index was slightly higher in the wetland (2.922) than in the river (2.707). Species assigned to Vulnerable, Near Threatened, Endangered, and Data Deficient categories were recorded in the study areas. Local fishers also reported declining catches in recent years. The findings provide baseline information on fish and macroinvertebrate assemblages in these freshwater systems and support continued monitoring and conservation-oriented management.