The Irrawaddy dolphin population of Chilika Lake is increasing, as per the recent census the number is 158 which is 9% more than the last years population. The annual dolphin census of Chilka Lake was carried out today. It is heartening to note that there has been an increase of the dolphin population by 9%. Before 146 dolphins each year annual population estimation of Irrawaddy dolphins (Orcaella brevirostris) of Chilika Lake is carried out during the month of February by Chilika Development Authority in collaboration with state wildlife wing and the volunteers and experts from various institutions. This is being carried out since from 2003
to monitor the status and population dynamics of Irrawaddy dolphin in Chilika. This year annual census of Irrawaddy dolphins was carried out on 16th and 17th February 2010. Pre-briefing of the census protocols to all the participants of the dolphin census was carried out on 16th February 2010 simultaneously at Wetland Research and Training Centre, Chandraput and Visitor Centre, Satpada of Chilika lagoon. Sri Bhagirathi Behera, Director Environment and Dr. A.K.Pattnaik, Chief Execitive CDA took the lead. The experts from office of PCCF Wild Life, RMNHS , CIFA, CEE, Ahmedabad, Utkal University, and a number of volunteers, NGOs participated in the census.
For population estimation the standard sighting method followed world over for estimation of aquatic mammals. The fundamental principle of almost all survey technique is a suitable and most befitting methodology which is site specific and animal specific in general. Generally survey is carried out covering the pre-determined survey routes. The transect method minimizes the chances of missing the dolphin groups or re-sighting of same dolphin groups. This methodology for Irrawaddy dolphin census in Chilika is adopted after detail review of various survey techniques used in wildlife census in general and in particular the cetacean survey techniques across the world. For the estimation of the population the transect survey method was adopted. Simultaneous survey along 20 transects by 20 survey team by use of 20 number of boat was carried out. 82 number of surveyor took part in the census. For precision the track routes were predetermined through computer programming and the track points were preloaded in to the hand held GPS. Each survey team were provided with a preloaded GPS to track the survey route. In addition to this to determine the exact distance rangefinders were provided to each team. Transect lines are designed in a planned manner so that the entire Lake is covered in a single day. The transect lines run fairly parallel to each other with a width of 0.8Km to 1.0Km. The width of these transect lines is roughly 1Km. Each team has to cover 500m focused area on right as well as 500m focused area on left side. An observer can have surveillance of 200m in naked eye and binoculars shall be used beyond 200m distance. Each team constituted of four members consisting of three observers and one recorder to record the observation. On 16th February 2010 the briefing and necessary input to all the participants were carried out simultaneously at Wetland Research Center Chandraput and at Satapada .
On 17th February 2010 the census was carried out. All the team took their respective positions at the starting points by 6.30 AM sharp. The team then started the survey by following their respective track. The visibility was excellent and the lake water was calm providing an Ideal situation for carrying out the survey.
From the survey 158 numbers of dolphins were counted out of which 129 were adult and 29 were juveniles including the neonates. Out of this 86 were counted in the outer channel and 72 numbers in the central and the southern sector of the lake. Out of the total population 55 % were recorded in the outer channel and 45 % in the lake proper. Last year 146 number of dolphin were counted from the lake, out of which 76 were recorded from the outer channel and 70 from the lake proper. There is an increase of 12 number of dolphin over the last year. Thus there is an increase in the population of Irrawaddy dolphin by 9% over the last year’s population in the lake. Dolphin being at the top of the food chain is a good indicator of the health of the lake ecosystem. The rise in the population of Irrawaddy dolphin in Chilika lake is thus a healthy sign. In Northern sector the population was recorded to be only 2 last year where as per the current survey it touched 6. The increase in the number can be attributed to the conservation initiative taken by the CDA and the wildlife department for protection and conservation of the Irrawaddy dolphin in the Lake.
CDA also running a research project to study the distribution, population dynamics, habitat utilisation, biology and the threat to the Irrawaddy dolphin population of Chilika lake. Based on the output of the study a conservation management plan of Irrawaddy dolphin would be developed. CDA is also carrying out an advanced underwater acoustic study of the Irrawaddy dolphin by use of hydrophones in collaboration with the Tokyo university. An International Workshop at Chilika on 23rd and 24th March 2010 on use of hydrophone for study of underwater behaviour of Irrawaddy dolphin in collaboration with the Tokyo University. This would provide useful clue for developing the conservation plan of the Irrawaddy dolphin of Chilika.
Puri News by Ranjan Ganguly