Population status, spatiotemporal distribution, and habitat drivers of endangered Ganges River dolphins in the Buriganga River, Bangladesh

The Endangered Ganges River dolphin, Platanista gangetica is increasingly imperiled by rapid habitat degradation and escalating anthropogenic pressures. This study assessed the population status, spatiotemporal occurrence, and key factors influencing the distribution of this freshwater dolphin along a 27-km stretch of the heavily polluted Buriganga River near Dhaka, Bangladesh, with an aim of informing management interventions. We applied combined direct count surveys and spatial analysis using habitat covariates to evaluate their occurrence in the river over a 12-month period from September 2023 to August 2024. Analysis of sighting data using N-mixture model yielded a detection probability of 0.24± SE 0.05, corresponding to a population of 19.79± SE 3.06 dolphins in the Buriganga River. Monthly and seasonal population variations were observed, with notable occurrence in December, and during winter season. The generalized linear mixed models identified river depth as a significant positive driver and boat traffic as a significant negative predictor for dolphin occurrence, while water temperature and dissolved oxygen exhibited weak, non-significant effects. We suggest enforcing the recommended vessel speed in core activity areas of dolphins for their future survival in the Buriganga River.