D. Multi-animal Acoustic Observation System
A more sophisticated hydrophone array system for precise monitoring of individual
animals in a group of dolphins has recently been proposed. The system shown in figure
4 consists of an array of hydrophones vertically separated by 1.6 metres. The central
portion has three hydrophones. The hydrophone signals are amplified and digitally
recorded in a PC-based recording and track analysis system.
The five hydrophones have the capability to accurately resolve several cetaceans at
the same time. Such a system has been designed and tested on bottlenose dolphins and
finless porpoises in Japan. The system has now been modified to be deployed horizontally
for shallow water operations in Chilika. $B!!(B
A picture of the hydrophone array being assembled for trials is shown in figure 5, with one of the hydrophones clearly indicated.
Results of tracking several dolphins (in different colours) are shown in figure 6.
The dolphin click trains are seen in lower left. On the right hand side plots we can
clearly see the individual dolphins resolved in depth as well as in the horizontal plane.
However, due to likely operational constraints of deploying a horizontal array in
shallow water in Chilika, depth information of dolphins is difficult to obtain.
The dolphins can be resolved in the horizontal plane.
E. First Trials in Chilika in January 2006
This will be the first time that Irrawaddy dolphins in Chilika will be acoustically
observed and surveyed using these technologies. The Japanese team consists of:
- Professor Tamaki Ura, University of Tokyo, Japan
- Dr. Tomonari Akamatsu
- Ms. Harumi Sugimatsu
- Mr. Junichi Kojima
- Mr. Hideyuki Takahashi
- Mr. Takashi Sakamaki
- Mr. Tomoki Inoue
In addition, the following experts will also participate:
- Professor R. Bahl, IIT Delhi
- Dr. Sandeep Behera, WWF_India, New Delhi
The team will bring two survey technologies:
It is proposed to use the 5-hydrophone system for initiating underwater
observation of Irrawaddy dolphins in Chilika. It is expected that movements of
several dolphins in a group can be independently monitored.
- A miniature acoustic data logger 12cm in length and 2cm in diameter will
also be tested. The system is expected to provide not only the migration timing
but also the rough number of animals that pass by the data logger system.
These systems will be brought from Japan by the 7-member team led by Professor Tamaki
Ura of University of Tokyo.
At this time, we would like to introduce the operation of these systems and discuss
the application of this new methodology for the conservation of isolated freshwater
Irrawaddy dolphins in Chilika lake. The trials will be jointly conducted with the
assistance of Chilika Development Authority (CDA), wildlife wing of Orissa Forest
Department and WWF-India. The team will share all data regarding the behaviour and
movement pattern of the Irrawaddy dolphins with the CDA, wildlife wing of State Forest
Department and WWF. Another advantage of this technique is that it may be possible
to acoustically recognize other dolphin species that may be present in the vicinity.
These trials will also help the team to carry out any further improvements in the
F. Future Plans
The Chilika experience will be a major first step for introducing and testing a
day-night automated acoustic survey system for different species of endangered
marine mammals. More ambitious surveys, including the endangered Ganges River dolphin,
would be planned jointly with the participating agencies.
Underwater Technology Research Center,
Institute of Industrial Science, The University of Tokyo,
4-6-1, Komaba, Meguro, Tokyo, JAPAN 153-8505