When water level is low, the concentration of animals in the rivers water pockets will be higher, helping wildlife scientists to avoid miscount or double count of the animals, Behera said.
To ensure further accuracy in counting the number and abundance of the animals, the survey is being conducted during the February end or early March, when the water level in the 2525-km long Ganga mainstream, besides its tributaries will be minimum and the weather too will be conducive for such exercise.
When water level is low, the concentration of animals in the rivers water pockets will be higher, helping wildlife scientists to avoid miscount or double count of the animals, Behera said.
The NMCG, which is executing the Namami Gange programme, mulls to conduct the study every two years.
Once the first survey is completed, it will give NMCG a baseline information for future studies, Behera added.
Meanwhile, sources in the Ministry said that the NMCG wanted to undertake the survey under its biodiversity restoration plan two years ago. However, it could not be launched due to lack of co-ordination among states.
UP carried out the survey, but adjacent Bihar did not.
Hence, the WII has been roped into co-ordinate with states and go ahead with the counting, a source said.
During the survey conducted in Uttar Pradesh between October 5 and October 8, 2015, as many as 1,263 dolphins were sighted in 3350-km stretch of Ganga and its tributaries in the state.
That census, a collaborative effort by the states Forest Department and WWF-India supported by NMCG, was done under the state government's "My Ganga, My Dolphin" campaign in 2015.
According to that study, stretches downstream Varanasi registered 269 dolphins and the 125-km stretch upstream of Fatehpur saw 175 dolphins.
Stretches of Ganga's tributaries Ghaghra, Rapti, Gandhak and Chambal had recorded an increase in their population whereas Ramsar site Brijghat to Narora recorded a decrease.
(This article has not been edited by DNA's editorial team and is auto-generated from an agency feed.)
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