Mapping hotspots and unveiling drivers of mortality in the endangered Gangetic Dolphin (Platanista gangetica) to mitigate human-mediated conservation conflicts in the Ganga River Basin, India

Abstract

Globally, effective conservation of threatened species hinges on robust population monitoring and the identification and minimization of threats that influence population dynamics. In the recent years, human-induced factors have surpassed natural causes as the primary drivers of species decline. Hence, information on human-induced threats of mortality and identifying spatial hotspots are critical for implementing timely and targeted conservation interventions. The Gangetic dolphin (Platanista gangetica) is widely recognized as a flagship species of river ecosystems in the Ganga River Basin, which has suffered population decline due to human-induced threats, including negative human-dolphin interactions. In the present study, we used a combination of a maximum entropy model (MaxEnt) and GIS-based weighted overlay analysis (WOA) to identify Gangetic dolphin mortality hotspots in the Ganga Basin. We compiled 110 records of Gangetic dolphin mortalities (n = 76) and rescues (n = 34) from diverse sources, including media reports, scientific articles, community volunteer network called the Ganga Praharis and basin-wide ecological surveys. The highest number of mortalities was recorded along the Hooghly River (38.2 %), followed by the Ganga mainstem (34.2 %), Sharda canal (9.2 %) and Girwa-Kauriyala rivers (7.5 %). The primary cause of mortality was accidental, such as entanglement in fishing nets, boat collision, dredging of river channels (32.9 %), followed by stranding in canal/barrages/shallow water (14.5 %), consumptive poaching (10.5 %), retaliatory killing (5.3 %), and natural causes (3.9 %). Using a combination of MaxEnt and WOA, we identified 770 km (15.1 %) of the river stretches as mortality hotspots associated with human-induced factors in the Basin. These identified stretches require urgent conservation interventions, such as the establishment of rescue and rehabilitation facilities, improved veterinary response system, and engagement with riverside communities to reduce the human-induced threats to Gangetic dolphin.