Fish biodiversity status in the river Mahananda near Katihar (India)

The River Mahananda, a tributary of the Ganga, sustains rich fish biodiversity crucial for the livelihoods and food security of local communities in Katihar, Bihar. There were 61 species in all, including native, food, sport, and decorative fishes, spread throughout 46 genera, 21 families, and 7 orders. According to trophic guild analysis, carnivores predominated, followed by herbivores, detritivores, and omnivores, indicating ecological equilibrium. Sanctuary stretches had better species richness (Shannon-Wiener Index, H = 2.50-2.53) than non-sanctuary zones, demonstrating the importance of protected regions for conservation. Relative abundance analysis revealed that economically significant species including Labeo rohita, Mystus cavasius, and Clupisoma garua were more prevalent. However, overfishing, destructive gear, sand mining, agricultural runoff, household pollutants, and habitat fragmentation pose serious risks to fish diversity. Numerous endangered and near-threatened species have declined as a result of these stresses, calling for immediate conservation action. It is essential to fortify fish sanctuaries, control fishing methods, restore habitats, and encourage community-based co-management. Ecological stability also depends on habitat connectivity and pollution control. The Mahananda River's ichthyological richness must be preserved for the region's socioeconomic stability as well as ecological health.