Patna, Oct 7  A day after the Ganga dolphin was declared a national aquatic animal, the state government has directed district officials to keep a close watch along the river-banks for the hunting and fishing of the marine mammals, officials said Wednesday.

Patna district magistrate Jitendra Kumar Sinha said the district administration has asked the block development officers, circles officers and sub-divisional officers to keep a close watch on the hunting and fishing of river dolphins.

Similarly, officials of Bhagalpur district said special measures would be enforced to check hunting of dolphins. Patna and Bhagalpur are two districts where dolphins were reportedly found dead in the past.

"All the district officials have been asked to be vigilant along the banks of the river Ganga for checking hunting and ensuring protection," an official told IANS here.

R. K. Sinha, a well-known expert on Gangetic dolphins said that dolphins are the lifeline of river Ganga. "If the dolphin numbers increase in the river, it will be a positive sign for a clean Ganga and if the numbers decrease, it is a negative sign of increasing pollution."

Bihar Chief Minister Nitish Kumar, alarmed over the dwindling number of the rare river dolphins in the Ganga, had announced a move to save the species two years ago. But the efforts did not move beyond government files, said Sunil Choudhary, a wildlife-expert.

The decision to declare the Ganga dolphin as an Indian national aquatic animal was taken Monday at a meeting of the newly-formed Ganga River Basin Authority (GRBA) in New Delhi that called for accelerated steps to clean up the river, revered as sacred by many Indians. The meeting was chaired by Prime Minister Manmohan Singh.

Sinha, who has been researching river dolphins for over two decades, also pointed out that immersion of idols during Hindu festivals poses a grave threat to the river and aquatic life. He suggested that "man-made water bodies" be used for immersing idols instead of the Ganga.

"The Ganga, which is already highly polluted, and its eco-system are under pressure and the immersed idols will create more trouble for dolphins and people dependent on the river for drinking water," said Sinha, a zoology professor at Patna University.

A report released by international NGO World Wide Fund for Nature (WWF) two years ago said the Ganga was among the 10 big rivers in the world facing extinction.

Untreated sewage, rotting carcasses and industrial effluents that find their way into the Ganga during its 2,500-km-long journey across several states from the Himalayas to the Bay of Bengal have also affected the dolphins, Sinha said.

Researchers estimate the dolphin population across India to be a little over 2,000. Half of these are found in the Ganga in Bihar and Uttar Pradesh. The numbers have dropped drastically over the past decades - in the 1980s, the Gangetic delta zone alone had around 3,500 dolphins. (IANS)