BHUBANESWAR: Is migration the reason behind a drop in Irrawady dolphins in Chilika? Worried over a decline in the number of the mammals this year, the Chilika Development Authority (CDA) has decided to set up a permanent station at the mouth of the 1,100 sq km lagoon to study their migratory behaviour. The annual census of dolphin for the year, which was carried January 16 and 17, put the population at 145. Last year, the cetaceans number was 156. The 10 per cent reduction in the population of the Irrawady, the CDA officials believe, could be due to the migration of the species from lake to the sea and vice-versa. “So far it could not be established based on the visual observations. We are proposing to install a permanent station at the mouth of the lake equipped with highly efficient hydrophone developed by Tokyo University, Japan,” Chief Executive of CDA Dr Ajit Kumar Patnaik said. One of the reasons why CDA strongly feels migration could be reason behind their lower number this year is there is a significant drop in mortality. Last year, just one death has been recorded while the number of calves has jumped from four to 11 which is a healthy sign of breeding. The CDA has an MoU with Tokyo University and the scientists from the latter would visit Chilika during April for the permanent station project. Once the permanent hydrophone array station is installed at the mouth, the movement of the dolphin can be definitely known, Patnaik said. This year, the population estimation survey was conducted with the line transect method. As many as 18 survey transects were created. The sampling of dolphin in each transect was carried out by a team of three, equipped with binoculars, GPS sets, rangefinder and data recording sheets. Ninety participants from different agencies took part in the census. Of the 145 dolphins, 118 were adults, 16 sub-adults and 11 were calves. The survey teams found 29 dolphins in the central sector, 41 in southern sector and another 75 in the outer channel. The Dolphin Motor Boat Associations also participated in the census while operation of the tourist boats was stopped during the census.
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