The World Wide Fund for Nature (WWF), Kolkata will start its Ganges river dolphin count in November after witnessing a dip in the number of the endangered species earlier this year.

"After the rains stop in October-November, we will undertake the survey along a 534 km stretch of Bengal in six-seven spots, but with a difference from previous practice," WWF Project Director (Bengal) Saswati Sen said.

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"When we zero-in on the Namkhana-Diamond Harbour stretch, we will link two points and scan the entire area.

Likewise along the Sabujdwip-Khamargachhi stretch in Hooghly district, two ends will be connected and the area surveyed," Sen, who was part of a team which scanned 45 spots for the previous survey earlier this year, said.

"This dolphin, a national aquatic animal, is not seen during rains and we will undertake the exercise when water level comes down in the river," she said.

Sen said while WWF-Bengal had previously conducted such surveys mostly based on sightings, this time "We wish to undertake the same exercise with equipment which help more accurate imaging." 

"Of the spots the team visited earlier this year, around 80 dolphins (Platanista Gangetica) were seen across a 500 km stretch and the number was less than the dolphins sighted four years back," Sen said.

This species of dolphins are seen in the Ganga-Brahmaputra river system in India and their total estimated number is 1,600, she said adding, the number of Dolphins in the Ganga will be clear after the next survey.

"We talked to people living on the banks of the river during the survey and they all confirmed that fewer dolphins are sighted these days," the WWF official said.

Asked about the factors, Sen said siltation and river water pollution were the main reasons as dolphin poaching was not a practice in the Gangetic belt of West Bengal.

"As part of sensitisation campaign, we are raising awareness among different target groups living along the river banks – hoteliers and panchayat members – reminding them how river pollution is affecting the ecosystem chain," she said.