Fish and macrophyte diversity in a tropical river under threat from municipal waste

Fishes thrive in balanced ecosystems, where threats like invasive fish species and extensive anthropogenic activity can significantly reduce native fish populations. Macrophytes play a crucial role in providing shelter and breeding grounds for small native fish species. This study was conducted to assess the fish and macrophyte diversity, water quality parameters, and potential pollution sources in a tropical river (Virinjipuram (Palar) River, Tamil Nadu) in India between January and March 2025. It also highlights the anthropogenic impacts on fish population. Our results show that 20 species were identified including 18 native and 2 exotic species (Oreochromis niloticus and Oreochromis mossambicus). Cypriniformes was the most dominant order with 12 fish species, followed by Perciformes (3 species), Cichliformes (3 species) and Siluriformes (2 species). IUCN global status of native species revealed 16 species as Least Concern, Parambassis lala as Near Threatened and Devario fraseri as Vulnerable. Five macrophytes were observed, indicating potential interactions between fish populations and macrophytes in influencing habitat dynamics. The presence of invasive species and extensive municipal waste dumping along the riverbank is of major concern. Our present finding suggests that measures have to be taken to mitigate the anthropogenic activities to conserve the native fish fauna.