Exotic and indigenous fish presence and distribution in the river Ganga at Varanasi

Abstract

The River Ganga at Varanasi is a critical habitat for both indigenous and exotic fish species, reflecting significant ecological changes in recent years. This study documents the presence and distribution of fish assemblages in this stretch, recording 82 species representing 8 orders and 28 families, with Cypriniformes and Cyprinidae as the most dominant groups. Indigenous species, including Indian major carps (Catla catla, Labeo rohita, Cirrhinus mrigala), have shown marked declines, while exotic species such as Cyprinus carpio (common carp) and Oreochromis niloticus (Nile tilapia) are now frequently recorded and constitute a substantial proportion of the catch. Environmental factors such as water quality, pollution, and anthropogenic activities have influenced species composition and abundance. The proliferation of exotics poses a threat to native biodiversity, necessitating regular monitoring and targeted conservation measures. The findings highlight the urgent need for sustainable management strategies to preserve the native ichthyofaunal diversity of the Ganga at Varanasi and mitigate the impacts of invasive species.