Assessing the patterns of fish assemblages in the Rupnarayan River, West Bengal in India

Tropical rivers, are highly biodiverse yet they face significant threats from human activities, impacting overall their ecological health. We studied fish diversity (richness and abundance) and its relationships with environmental factors, understanding size class distribution and the role of land use land cover in a Rupnarayan river in east India. Using a hierarchical nested design and space-for-time replacement method to sample fishes from January 2024 to March 2024 over a 30 km stretch of the river. We recorded 40 species, comprising 774 individuals from 14 orders and 25 families. Multiple linear regression indicated that channel type, water temperature, river width and depth, and time spent on fish sampling were significantly associated with species richness and abundance. Flow-ecology relationships demonstrated a preference for slower currents among selected species. The fishing gears influences the body size class of fish species. Land Use Land Cover analysis showed that cropland (44%) dominates the study area followed by vegetation (25%), built-up areas (18%) etc. Despite the absence of immediate threats, the Rupnarayan River plays a crucial role in supporting significant riverine biodiversity which may be helpful for future ecological research and conservation efforts in similar tropical rivers in the world.