Patna: Endangered river dolphins are winning a battle for survival in the only sanctuary of its kind in India along a protected stretch of the Ganges river, wildlife officials say.

In the last 10 years, Dolphin numbers have risen to about 100 from 34 in the 60 km- long Vikramshila Gangetic Dolphin Sanctuary, in Bihar, said D N Chowdhary, a senior professor at Bihar's Bhagalpur University.

"Owing to the efforts of wildlife enthusiasts, officials and directions given by the Patna High Court, the number of dolphins has risen," he said.

Some Indian courts are known to take up environmental issues as part of what is known as public interest litigation.

"This sanctuary has at last proved a safe stretch for river dolphins who are fast becoming extinct in other river systems of the world," Chowdhary said.

Of the 40 species of dolphins worldwide, only four are found in fresh water, in China's Yangtze River, the Amazon river system of South America and the Indus-Ganges river system of South Asia, Chowdhary said.

"The Ganges, Brahmaputra and Indus rivers now account for the majority of the river dolphins. That is why this project is very important," he said.

State officials are hoping the dolphin sanctuary, which lies 300-km South East of Bihar capital Patna, would become a tourist attraction and give locals one more reason to protect the animals.

The state's Mandar Nature Club has been educating the locals, including fishermen, about the need for a safe haven and maintaining the delicate balance of the Ganges.

Efforts were further galvanised when the Patna High Court intervened to urge support for the conservation programme from state officials.

In the past, poachers would hunt the dolphins for their flesh as well as fat. But a tight vigil in the recent past has helped police catch some poachers, significantly reducing killings.

"The numbers should increase, as there is now greater awareness and alertness about their protection and preservation," said R K Sinha, the head of the dolphin protection programme.

River dolphins, like those in the sea, are highly intelligent. References to them in Eastern India's Ganges river can be found in artefacts dating back to 246 BC, the time of king Asoka.

The king converted to Buddhism after witnessing a brutal war and then banned the killing of several species of animals, including the river dolphin. Pre-historic rock paintings of creatures resembling the animals found in the state's Kaimur hills point to local people's affection for them.