Scientists from University of Tokyo have started acoustic tracking of endangered Irrawaddy dolphins in Chilka lake using sophisticated Underwater Array System. The system being used for the first time in the country was installed at Magarmukh, Satpara region of Chilka on January 29.
Dr Sandeep Behera, Co ordinator, Freshwater and Wetlands Programme of Worldwide Fund for Nature in an exclusive interview to the Hindustan Times said, “The system is working fine and we are receiving a lot of data from the dolphins underwater”.
The project is being undertaken in collaboration with University of Tokyo, Chilka Development Authority, WWF India and Forest Department of Orissa government.
He said Irrawaddy dolphins being the only known marine mammals in Chilka lake were also on top of the food chain and thus their health indicates the state of the entire ecosystem.
“The dolphin population of Chilka is only around 120 with ten to twenty dolphins dying every year, some after hit by motor boats ferrying tourists, others due to low water levels and increased salinity and some by shark bites,” he said.
“During the last 2-3 years the population of Irrawaddy dolphins has been stable but as we are still getting death reports, we surmise that dolphins may be coming from outside.”
“The Underwater Array System if kept at the mouth of Chilka will not only help us monitor dolphin population but also keep track of migration of dolphins in and out of the lake” he added.
He explained that dolphins like bats emit ultra-sonic ‘clicking’ sound regularly and use the echo to create image of their surroundings for navigating safely in the water and also catching their prey.
Last year the Japanese team led by Prof Tamaki Ura had conducted extensive studies in the lake with frequency metres to scan and find the right frequency at which dolphins emitted their click-clicks.
“They found that dolphins emit ultra sonic clicking sound at the frequency of 100 Mega Hertz. This year Japanese scientists were back with specialised hydrophones to catch the ‘click’ of dolphins. The Underwater Array System has five hydrophones facing different directions underwater.”
The computer based tracking system can indicate the movement of dolphins on the screen, can count their numbers and also tell whether they are going to attack a prey or busy feeding, he added.