JOIN USOfficial sources said Nitish has directed the district magistrates of Patna, Bhagalpur and Buxar to see that the ban order has been adhered to.
Officials have been asked to keep close surveillance along the Ganga river banks to stop the hunting, the District Magistrate of Patna, J K Sinha, said.
Patna and Bhagalpur districts are the two districts where dolphins have been reportedly found dead in the past
The decision to declare the Ganga dolphin as an Indian national aquatic animal was taken at a meeting of the newly-formed Ganga River Basin Authority in New Delhi that called for accelerated steps to clean up the river.
The meeting, which took place early this month, was chaired by Prime Minister Manmohan Singh.
Early this year, alarmed at the death of about six endangered Ganga river dolphins in Bihar, wildlife activists had called for urgent action.
Around six dolphins were killed by poachers and fishermen in the last one month alone in the Vikramshila Gangetic Dolphin Sanctuary, one of the four freshwater dolphin sanctuaries in the world.
The head of the zoology department of Patna University, R K Sinha, had warned that the mammals would disappear unless urgent steps were taken to clean up the Ganga.
Sinha, a well-known expert on Gangetic dolphins, said that dolphins are the lifeline of the Ganga. ''If the dolphin numbers increase, it will be a sign for a clean Ganga and if the numbers decrease, it is a sign of increasing pollution."
Sinha, who has been researching river dolphins for over two decades, also pointed out that immersion of idols during Hindu festivals posed 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.
A report released by international NGO World Wide Fund for Nature 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.