The number of Irrawaddy dolphins in Chilika has dropped to 145 from an estimated 156 last year and 158 in 2010, according to the latest census data.

BHUBANESWAR: The number of

in Chilika has dropped to 145 from an estimated 156 last year and 158 in 2010, according to the latest census data.

Dolphin census was conducted in the brackish water lake on Monday and Tuesday. Chilika, a Ramsar site (i.e. a wetland of international importance) since 1981, incidentally, has the largest lagoonal population of Irrawaddy dolphins in the world, ahead of Lake Songkhla in Thailand.

"The slight reduction of estimated number of dolphins compared to the 2010 and 2011 could be due to migration of species from lake to the sea and vice-versa, though so far it has not been established through visual observations," said chief executive of

(CDA) Ajit Patnaik. Installation of a permanent station, equipped with highly efficient hydrophone array, developed by Tokyo University, Japan, at the mouth of the lake was on the cards, he added.

A memorandum of understanding has been inked between CDA and the Tokyo University and scientists from the foreign varsity would be coming to Chilika during April, Patnaik informed. "Once the permanent hydrophone array station is installed at the mouth, movement of dolphins can be definitely known," he pointed out.

During this year's dolphin census, it was found that the number of calves has increased from four in 2011 to 11 this year and the number of causality has reduced to one, from 10 in 2009.

The dolphin census was done following Line Transect method, official sources said. "The total number of survey transect was 18. A team of three persons carried out sampling of dolphin/group of dolphin in each transect. Each team was equipped with binoculars, GPS set, rangefinder and data recording sheets, etc," an officer said.

Sources said 90 people from different organizations including state government's wildlife wing; WWF-India, New Delhi; Odisha Watershed Development Mission; BNHS, Mumbai; Regional Museum of Natural History, Bhubaneswar; Centre for Environment Education, Bhubaneswar; researchers and academicians; Wildlife Society of Orissa; Chilika Wildlife Division, Chilika Development Authority, animal resource development department, Local NGOs and local motor boat associations participated in the census operation. In addition, 40 local volunteers were deployed in 18 boats.

L The number of Irrawaddy dolphins in Chilika has dropped to 145 from an estimated 156 last year and 158 in 2010

L the number of calves has increased from four in 2011 to 11 this year and the number of causality has reduced to one, from 10 in 2009

L Around 90 people from different organizations, including the state government's wildlife wing and WWF-India, participated in the census operation