Sounding the alarm for Irrawaddy dolphins

A two-day workshop in Bhubaneswar,starting March 25,attended by researchers from Japan and India,stressed the need for technology in the conservation of Irrawaddy dolphins.

As the dolphins communicate with each other through ‘clicks’ with a frequency of 40-60 kilohertz—the human ear cannot pick up frequencies above 20 kilohertz—a set of hydrophones,that is,microphones that work under water,developed by Tamaki Ura of the Underwater Technology Research Centre (UTRC) of the University of Tokyo,will now be deployed in the lake. “By a complex system of echolocation,dolphins can determine the size,shape,speed,distance,direction,and even some of the internal structure of objects in the water. They are able to learn and later recognise echo signatures returned by prey species,” said Ura. The array of eight customised hydrophones with an in-situ data capturing system can capture data without interruption,which can then be used to interpret the underwater behaviour of the dolphins.

“Dolphins in Chilika face the biggest threat from fishermen and tourist boats. The new technology can be used to identify their social groupings,and help regulate the movement of boats and fishermen,” said Dr BC Choudhury,senior scientist of the Wildlife Institute of India,Dehradun. The 700-odd motorised fishing and tourist boats trawling the lake also kill many unsuspecting Irrawaddys that cross their path.

Officials of the Chilika Development Authority,the Orissa government body formed to develop and conserve the flora and fauna of the lake two decades ago,are hopeful that the new technology will help determine the response of the dolphins to approaching objects and noise. “This will help us develop a protocol for dolphin watching. It will also determine the size,shape,speed,distance,and direction of movement of the dolphins,and their migration within the lake and outside,” said Ajit Patnaik,chief executive of CDA. The CDA has signed an MoU with the University of Tokyo to develop an advanced observation system for Irrawaddy dolphins.

Between 2007 and 2009,a million visitors thronged the lake to see the dolphins frolicking in the water. “We earned Rs 24 crore from these visits,” said Bishnu Prasad Behera,dolphin researcher with CDA.

“Aquatic mammals need to come out of the water once in a while to breathe. Fishermen’s gillnets are like deathwalls for them,” said P Dhandapani,former scientist with the Zoological Survey of India,who between 1985 and 1987 re-discovered the dolphins in Chilika during an expedition.