Odisha government’s first ever survey of dolphins in lakes other than Chilika on Sunday showed that at least six species of dophins are in existence in these lakes.
Conducted by the Wildlife Wings of Odisha, the enumeration of dolphins in the state was taken up in coastal divisions of Balasore, Bhadrak, Bhitarkanika, Puri, Chilika and Berhampur.
Usually, the survey was conducted in Chilika lake every year in collaboration with the University of Tokyo using its customised hydrophones to record the sounds of dolphins under water, especially for observing the underwater behaviour of Irrawaddy dolphins.
Bhitarkanika, known for estuarine crocodiles and Olive Ridley turtles, for first time reported to have six species of dolphins — Bottlenose, two species of Humpback, Pan Tropical Spotted, Irrawaddy and Finless Porpoises.
In all, 9 teams with 31 enumerators have been deployed for the census, five of them in coastal regions and four in the creeks at the Bhitarkanika Marine Sanctuary. About 40 wildlife experts and forest officials have been pressed into the headcount exercise, officials said.
Chilika, where the annual census of Irrawaddy dolphins is undertaken, has been covered entirely this year with 18 teams comprising 90 members deployed for the census.
Officials said Line transect direct sighting method was used for the census. Line-transect surveys rely on the critical assumptions such as (1) the probability of detection on the trackline equals one (i.e. g(0) = 1), or at least known; (2) animals are detected prior to responsive movement; (3) measurements are recorded accurately, with no observer bias; (4) line-transects are located randomly with respect to the distribution of the animals; (5) detections are independent events.
Unless strictly adhered to these assumptions, the results will be biased, say experts. The entire data and a comprehensive report on the number of dolphins in the state will be released in a day or two. It is expected that 12 different species of dolphins will figure in the report this year from Odisha coastal region.
In addition, 3 teams of 5 members each have been sent along the 150-km Puri coast with two trawlers and two boats. These enumerators have been trained in species identification, sighting and recording to facilitate the census. They have also been provided with binoculars, GPS equipment and data recording sheets, added officials.
The entire area from Udaipur in Baleswar district to Pati Sonepur in Ganjam district has been covered for the census this time.
The Irrawaddy Dolphin population of Chilika Lake was at 158, recording an increase of 9% every year in 2014.