Factors affecting the survival of Indus River dolphin and species tolerance towards anthropogenic pressures

There is broad consensus among ecosystem experts that river dolphins, as top predators, can structure riverine ecosystems and benefit biodiversity. The effects of dolphins on rivers and vice versa do not operate in isolation, but are context dependent, being conditioned by other factors such as human interference. Based on the aforesaid presumption, the focus of the present study was on quantifying the factors responsible for the decline of the Indus River dolphin and species tolerance towards these factors in the upper sub-basin of the Indus River system (River Beas, India). Dolphins avoided (r = -0.667; P = 0.001) the study section with higher disturbance, until some other factors, such as prey availability, came into play. Species occupancy was significantly different for different flow seasons and was associated with deep pools, eddy currents, and low disturbance index. The results indicated a marked decrease in species occurrence above a disturbance index level of 44. The findings of the present study contribute towards a better understanding of the complex ecological interactions of river dolphins with their environment and provide valuable insights into the wider conservation status of other threatened components of sympatric freshwater biodiversity that can further help in designing effective conservation measures for the ecosystem as a whole.