Beneath the heavily silted waters of our Himalayan Rivers dwells a strange creature, discovered in Calcutta in 1801, now known to science as Platanista gangetica or the Ganges river dolphin. This river dolphin is truly an odd animal to behold. This relatively ancient cetacean has almost lost its visual powers, as eyesight in a sediment-rich river is quite a costly sense to have. Since sight is compromised in sediment-rich rivers like the Ganga, the animals have evolved to rely exclusively on sound in order to navigate and forage.
After my first sighting of the river dolphin in Calcutta, I was truly surprised for I had never imagined this relic of an animal to still live within the city because of the current state of the river. Apart from being a carrier of sewage, plastic, oil and chemicals, the Hoogly River is also one of the busiest waterways in the entire country. There are numerous ghats along the river. A motorised boat with a capacity of at least 100 people sets off from one ghat to another at an average frequency of once every 10 minutes. In addition to this, gigantic vessels carrying shipping containers and barges carrying coal are scattered all over the river with sooty smoke steaming forth from their funnels.
This heavy vessel traffic on the Hoogly River unfortunately creates a lot of noise underwater. Since the Ganges River dolphins rely on sound for their daily functioning, continuous interference and unwanted noise in the Hoogly River can surely affect them. A stark contrast to the Hooghly River in Calcutta is the Ganga River in Bihar, where the sounds of shrimps, fishes and dolphins fill up the entire water column, and an occasional whirring motor boat drowns the sound produced by these animals. Imagining a scenario where the Ganga River is transformed into a channel with high vessel traffic is truly terrifying.
Without well designed studies, one may never know how this noise pollution in our rivers is affecting the Ganges River dolphins. An indication of the possible effects can be found in the Yangtze River in China, which was once home to the Chinese river dolphin. Increasing noise in the river is considered to be one of the causes for the extinction of their river dolphin. Could it be that our river dolphins will suffer the same fate as the Chinese river dolphin because of the extent of modifications planned on our rivers?
The fact that the Ganges River dolphins are still managing in the Hooghly River cannot be an indication that waterways have no impact on our river dolphins. We do not know the extent of damage continuous noise in the Hooghly has had on the Ganges river dolphins. Unlike the Ganga, where dolphins are fairly easy to spot, one needs to spend hours searching frantically and straining the eye in hopes of seeing a dull brown animal emerging from the depths of the river to breathe. In fact, the dolphins are just one small measure of the health of the river, and one must involve studies on the responses of other biological taxa to the rapid and rampant modification of our rivers. Only then, can we holistically understand the condition of most of our rivers, both ‘urban’ and ‘wild’, and those that are, or once were, home to river dolphins.
We can read detail story by Mayukh Dey here.Mayukh Dey:
Mayukh Dey is part of the current MSc Wildlife Biology and Conservation cohort of the National Center of Biological Sciences, Bangalore. Having previously worked on projects involving crocodiles, otters and the Ganges River dolphin, he has been affiliated with freshwater systems for the past three years. Here, he writes about his concerns for the river dolphin that lives in India’s noisy waterways.
