Although the endangered Gangetic dolphin used to be seen along the entire stretch of the river, today it continues to thrive in specific stretches of the Ganges. Given the rate of biodiversity loss and structures along this river, their survival, as well as that of a number of fish species, hangs in a delicate balance.
Vice Chancellor of the Nalanda Open University RK Sinha, also a biodiversity expert, said the dolphin situation in the Ganges was better than in China where the river dolphins have become extinct.
Commonly known as susu (shushuk in Bengali), these dolphins are generally present all along the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, Bangladesh and potentially Bhutan. Their schools stretch from the deltas to as far up as is navigable for them.
The susu disperse from the main rivers to the floodplains and tributaries in the monsoons and return to the main river stream in the drier months. Dolphin sighting remains high in the lower and middle stretches of the Ganges. They continue to thrive in specific stretches of the Ganges for which Dr Sinha credited massive awareness campaigns from the government, as well as NGOs, to educate fishermen and general people. Even the courts have played a part to prevent killing of dolphins, says the biodiversity expert.
Referring to similar studies 30 years apart he said it was not that the number of fish species had decreased. “But the economically important species have gone down while exotic species have increased.” RK Sinha said he had identified 106 species in a survey 30 years ago. A similar survey found the the same number of species in 2009. “But there were 10 more exotic species.”
“But the economically important species have gone down while exotic species have increased.”
Overall, however, Dr Sinha is certain about the loss of flora and fauna over the last four decades that he has been studying the Ganges. He said, “Hilsa is totally gone. At the same time Rohu, Katla, Nani and many catfish have seen their population decline.”
He said pollution and excessive use of pesticides and insecticide keep these fish from breeding.
Pollution levels reach unbearable proportion over certain stretches of the Ganges during the dry season that might have been much less with stronger water flow.
RK Sinha says the main production of carps has now become fish culture instead of the river catch, which he suggests is also an indication about the loss of biodiversity in the holy Ganges.