AMID the impenetrable maze of tidal creeks and channels between India and Bangladesh, children shriek with delight as grey snouts emerge from the silty waters. “Susu,” they cry, mimicking the noise the freshwater dolphins make as they surface for air — but their joy may be shortlived.

Researchers say that the Gangetic dolphin, declared one of the world’s first protected species more than 2,000 years ago, during the reign of Emperor Ashoka (265-232BC), has already become extinct in the main tributaries of the Ganges river system.

According to a study by the WWF, formerly the World Wide Fund for Nature, the freshwater dolphin population in the Ganges has shrunk from 6,000 in the early 1990s to 1,500 in 2005, with a complete absence in some tributaries.

The Ganges drainage area is home to about a tenth of the world’s human population and suffers enormous demand for its resources.

A growing threat to the dolphin population has been the extensive damming of rivers for irrigation and electricity generation, which isolates family groups and prevents seasonal migration. Pollution of the Ganges has also become so bad in parts that bathing in and drinking its water has become extremely hazardous for much of its 2,500- kilometre (1,550-mile) stretch from the Himalayan foothills to the Bay of Bengal. Equally troubling is the increased hunting of the dolphins for oil, fish bait and food by local people.

According to R. K. Sinha, head of the zoology department at Patna University, who has been studying the mammals for a decade, the dolphins will disappear unless urgent steps are taken to clean up the river. “They are facing extinction,” he said. “Their falling numbers show they will soon disappear from the Ganges altogether. Our researchers estimate the dolphin population across India to be a little over 1,500 and the numbers have dropped drastically over the past decade. The river is highly polluted by the time it reaches Patna, some 1,700 kilometres downstream from its source. Fishermen are known to kill dolphins to use their fat to prepare fish bait. They also net them and slit them open to drain their oil, which is sold locally to cure joint pains.”

The Gangetic dolphin is one of only four freshwater species in the world. The other three are found in the Yangtze river, in China, the Indus, in Pakistan, and the Amazon and Plata rivers, in South America. According to the WWF, all four are in trouble.

In one stretch of the Ganges, however, there is some hope as the number of dolphins has nearly doubled, from 22 to 42, in the past decade. Sandeep Behera, the head of the local protection programme, said that a ban on fishing and environmental degradation on a stretch of the river 200 kilometres southeast of Delhi had helped to replenish stocks.

“The worst threat is pollution, the second is fishing activity and the third is habitat degradation,” he said. “In this particular stretch, however, we have overcome the threat of fishing activity as the local government has banned commercial fishing and sand-mining activities along the banks. We have also worked closely with religious leaders, who in turn work with us to motivate the local people, reinforcing the holy nature of the Ganges in our religion.”

FINDING ITS WAY IN THE DARK

Found only in fresh water, they migrate to tidal waters during the monsoon season

Times Recommends

• Mandela’s tribe threatens President Zuma
• The French empire strikes back
• Wife of cheating governor exacts a political revenge