Nainital – Scientists at the Wildlife Institute have developed double observer mark-recapture technology.
Counting dolphins, all of them similar in appearance, sometimes jumping on the surface of the water and then disappearing within a few seconds, is like finding a needle in the sand. But now this will be easier with the double observer based mark-recapture method developed by the scientists of Wildlife Institute of India for accurate counting of dolphins.
Using this method of identifying dolphins through sound waves, a successful survey has been conducted over a distance of about nine thousand kilometers from Bijnor to Ganga Sagar and the report has been submitted to the Central Government. Indian Wildlife Institute scientist Dr. Vishnupriya Kolipakam and scientist Qamar Qureshi told that the dolphin comes to the surface every two to three minutes for one to one and a half seconds to breathe. Accurately counting dolphins that are similar in appearance is quite a challenging task.
The technology was developed after about four-five years of hard work. On the basis of which, a survey of about nine thousand kilometer area of Ganga and its tributaries has been done from Bijnor in UP to Ganga Sagar. The first phase survey was completed from October 2021 to March 2022 and the second phase survey was completed between October 2022 to March 2023.
The survey was completed with the help of 70 researchers. The number of dolphins has been given area wise in the report. Soon the data of the report will be made public by the Central Government. The Prime Minister announced Project Dolphin in August 2020. Under which there will be comprehensive monitoring of dolphins in rivers every three years. Whereas in the dolphin hotspot area, monitoring is to be done every year. In such a situation, the technology developed will prove helpful in accurate monitoring of dolphins.
Survey was also done in these tributary rivers
- During the survey from Bijnor to Ganga Sagar, tributaries Gagra, Sharda, Rapti, Gandak, Mahananda, Kosi, Roopnarayan, Bakshi, Brahmaputra, Chamba, Sundarban etc.
Sound signature tells the different identity of every dolphin
The double observer based mark-recapture technique developed involves monitoring the dolphins from different locations in the boat. Along with this, the angle of the dolphin and its sound signature are recorded through hydrophone, GPS, underwater recorder etc. The individual identity of each dolphin is determined by measuring the distance and angle of sound waves recorded at 70 kilohertz. To ensure that a dolphin does not overtake a boat moving in the water, the speed of the boat is kept at eight to ten kilometers per hour.
That’s why the growth rate of dolphins is very slow.
The growth rate of dolphins is quite slow. They have one child born every 2-3 years. Which is increasing the risk of their increase. According to a survey conducted in December 1996, no dolphins were recorded in the 100 km stretch of the river Ganga between Haridwar’s Bhimgoda Barrage and Bijnor, while the total estimated population of dolphins in the Uttar Pradesh section of the Ganga was recorded at only 500.
