• Rise in salinity in the water system that makes the Indian Sunderbans has resulted in the decrease of population of the Ganges River Dolphins in the region.
  • A recent study covering 100 km of rivers and channels around the Sunderbans have revealed that the national aquatic animal is no longer sighted in the central and eastern parts of the archipelago.
  • Only in the western part of Sunderbans, where the salinity is lower, could researchers find some evidence of the species.
  • Freshwater flow to the Sunderbans is crucial for the subsistence of these species.
  • The hyper-saline zone in the central part of the Sunderbans, which includes areas such as Raidighi and Patharpratima, have lost connectivity with the upstream freshwater flow.
  • Though there is some fresh water connectivity and flow in the eastern part, salinity levels were still high and thus there was no evidence of the Ganges River Dolphin in this region.
  • The rise in sea level, triggered by climate change, is one of the reasons for the increase in salinity of waters of rivers and channels.
  • Hydrological modifications like water diversion and commission of large barrages upstream have had a great impact on the salinity profile of the rivers downstream in the Sunderbans.
  • Classified as endangered by the IUCN Red List, the freshwater species was also once found in different tributaries of the Ganga in West Bengal.
  • Researchers and experts pointed out that the sighting of the Ganges River Dolphin has decreased over the years in the 534-km stretch from Farakka Barrage to Sunderbans.
  • At present the population of the Ganges River Dolphin is confined to some pockets like Nabadweep, Kolaghat, Diamond Harbour and Namkhana.