both subspecies have been adversely affected by human use of river systems in south asia. entanglement in fishing nets as by-catch can cause significant damage to local populations, and individuals are taken each year by hunters; their oil and meat used as a liniment, as an aphrodisiac, and as bait for catfish. poisoning of the water supply from industrial and agricultural chemicals may have also be a contributing factor towards population decline, as these chemicals are bio-magnified in the bodies of the dolphins. perhaps the most significant issue is the building of more than 50 dams along many rivers, causing the segregation of populations and a narrowed gene pool in which dolphins can breed. an immediate danger for the ganges subspecies in national chambal sanctuary is the decrease in river depth and appearance of sand bars dividing the river course into smaller segments, as irrigation has lowered water levels throughout their range.