Assessment of Flood Impacts on Fish Biodiversity in the Swat River, Pakistan

Abstract

The Swat River originates from Mahodand Lake as the Peshmal stream of Ushu before merging with the Utror stream. The river experienced severe flooding during two major periods, July 29–31, 2010, and August 26–29, 2022, which greatly disturbed its biodiversity and caused substantial damage to fish fauna. To assess the impacts of these floods, fish samples were collected from different sites and preserved in formalin for identification. Population density and species abundance were evaluated before and after the flood events. A total of 17 fish species belonging to different orders and families were recorded from various months and locations after the floods. Interestingly, four native fish species of the Swat River, namely Glyptothorax cavia, Xenentodon cancila, Channa punctatus, and Puntius sophore, were absent in the present study. Questionnaire data obtained from fishermen revealed that Schizothorax esocinus, Tor putitora, and Labeo dero are threatened and rarely encountered. The study concluded that fish populations declined by 42–51% after the severe floods of 2010 and 2022, mainly due to habitat destruction and ecological losses caused by flooding.