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A population of endangered Gangetic river dolphins has been found for the first time in the Mahananda river, a tributary of the Ganga, in Bihar’s Kishanganj district.
A team of scientists from Vikramshila Biodiversity Research and Education Centre (VBREC) of Tilka Manjhi Bhagalpur University, spotted the 14 Gangetic river dolphins during a survey.
“Never before had any survey been conducted to search for dolphins in the Mahananda in Bihar. It is a positive development that dolphins were found in the first survey itself,” Sunil Choudhary, director of VBREC told Down To Earth.
The survey was conducted in March-April 2019.
There was secondary information that dolphins had been spotted in the Mahananda in neighbouring Araria district during monsoon floods, said Choudhary. Environmental activist Sudan Sahay had reported this long ago.
“But it was not verified. We have conducted the first survey and found dolphins in the Mahananda and its four tributaries,” he said.
The survey team spotted seven adult dolphins and seven calves. No juvenile was spotted.
Another survey?
Choudhary said the survey was not conducted in a suitable season. If it had been conducted from July to February, the results would have been different.
He added the team had submitted the survey report to the Bihar government and recommended a fresh survey to be conducted in the Mahananda from October 15 to February to study the exact number of dolphins.
“We strongly feel the number of dolphins in the Mahananda and its tributaries are much more than what we had spotted during the survey, under unsuitable conditions,” said Choudhary.
He pointed that when the team was conducting the survey, there was inadequate water level in the river and it was difficult to use even a boat for navigation to examine the dolphins.
“Only after the monsoon ends would the real number of dolphins in the river be known as there would be adequate water level”.
RK Sinha, known as 'India’s Dolphin Man', said the presence of dolphins was the sign of a healthy river ecosystem. Dolphins prefer water that is at least five to eight feet deep. They are usually found in turbulent waters, where there are enough fish for them to feed on.
Gangetic dolphins live in a zone where there is little or no current, helping them save energy. If they sense danger, they can dive into deep waters. The dolphins swim from the no-current zone to the edges to hunt for fish and return, Sinha said.
A threatened species
Demand for water from the river has been increasing with the rise in temperature. “We need more water. As a result, water level is declining in the river, putting more pressure on the dolphins to manage their life cycle,” said Sinha.
Experts agree the Gangetic dolphins' habitats face serious threats from climate change. They point that increasing pollution due to largescale discharge of industrial and municipal waste, siltation, and mechanised boats pose the biggest threat to these freshwater dolphins.
The Gangetic river dolphin is India's national aquatic animal but frequently falls prey to poachers. Their carcasses are found regularly on river banks.
Gangetic river dolphins fall under Schedule I of the Indian Wild Life (Protection) Act and have been declared an endangered species by the International Union for Conservation of Nature (IUCN).
The Gangetic river dolphin is one of the four freshwater dolphin species in the world. The other three are found in the Yangtze river in China, the Indus river in Pakistan and the Amazon river in South America.
The Gangetic river species — found in India, Bangladesh and Nepal — is blind and finds its way and prey in the river waters through echoes. These dolphins live by echolocation and sound is everything to them. They navigate, feed, escape danger, find mates, breed, and nurse babies by echolocation.