Plans are afoot to count Gangetic dolphins in the rivers of the state afresh.

A proposal in this regard was sent to the Centre earlier. The National Mission for Clean Ganga (NMCG) has given go-ahead for the project, a senior environment and forests department official told The Telegraph on Tuesday.

NMCG is a registered society and is the implementing wing of the National Ganga River Basin Authority (NGRBA).

The official said the Centre had tagged the project with a World Bank-funded scheme. The exact amount to be released to the state for the exercise had not been communicated yet.

According to the proposal details, four teams would be drafted for conducting the survey and the groundwork is likely to be carried out in October and November this year. Some of the major rivers that would be surveyed under the project are the Ganga, Gandak, Sone, Ghaghara, Kosi, Mahananda, Bagmati, Punpun and Budhi Gandak among others.

"Surveying all these rivers, which flow in the Ganga basin area, is a must to know the exact number of Gangetic dolphins in Bihar. These mammals have a tendency to swim to smaller rivers during the rainy season in search of food. Once the water level recedes after the rainy season, many get entrenched in the smaller rivers and become vulnerable. A knowledge about their presence in different rivers would help the forest department officials to ensure their safety in the habitat," dolphin expert R.K. Sinha said.

Sinha had played a key role in getting the Gangetic dolphins the status of national aquatic animals in October 2009.

Fresh water fishes, the main prey of dolphins, have a tendency to swim against the current. During the rainy season, several of them enter smaller rivers while flowing against the current and dolphins do the same chasing them.

An instance of Gangetic dolphins getting trapped in a small river had come to light in 2013 when two aquatic mammals were found in Tonk river in Kishanganj district of Bihar. Zoological survey of India scientist Gopal Sharma had rescued them.

Dolphin expert Sinha had surveyed the river Ganga and a part of river Gandak (Patna to Tengrahi Ghat in Gopalganj district, 152km) to count the number of dolphins in a state-sponsored exercise in 2012. During that survey, as many as 756 dolphins were spotted in around 500km stretch of the Ganga flowing through Bihar and 84 were spotted in the Gandak.