Irrawaddy Dolphin Population at Chilika Lake increases

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The population of the rare Irrawaddy dolphins (Orcaella brevirostris) at the Chilika Lake, Bhubaneswar in the Indian state of Orissa has increased, shows the figures released by Chilika Development Authority (CDA) after a recently concluded census of the dolphin population in the lake. According to CDA, the dolphin population in the lake has increased by 4.6 percent when compared to last year’s census figures.

Irrawaddy dolphin (Orcaella brevirostris)

Image Courtesy: Wikimedia Commons

     Irrawaddy dolphin (Orcaella brevirostris)

During the survey which has taken place from January 18 to 19 this year, teams were able to spot a total of 152 dolphins among which 118 were adults while 16 were sub-adults and 18 were calves and newly born dolphins.

Moreover, the survey teams have also sighted at least eight dolphins in the northern sector of the lagoon. According to experts, this sighting is an indication that the dolphin population in the lake is expanding the habitat.

The rate of presence of calves and neonates has also increased compared to last year’s figures. According to Ajit Patnaik, chief executive of CDA, there has been a 38.9 percent increase in the presence of calves and neonates in the lake.

Line transect method used for sampling

The survey has used the line transect methodology to assess the population of dolphins in the lake. According to sources at CDA, the survey used a total of 18 transects and the sampling in each transect were taken by teams of 7 to 8 members which had at least 3 experienced persons. 10 teams were deployed at the main lagoon while 8 teams at the outer channel and northern sector of the lagoon.

A view of Chilika Lake, Bhubaneswar, Orissa
Image Courtesy: Wikimedia Commons

A total of 130 persons from different organizations and institutions participated in the survey.  To facilitate smooth survey process with accurate sampling, the usual tourist boat services in the lake started operating only after the completion of the census process during the census days.

Geographic distribution of Irrawaddy dolphins

The survey results are a green signal as the population trend of these rare aquatic organisms, according to IUCN, is declining worldwide. At present, it is present only in Asian countries like Bangladesh, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Viet Nam in addition to India. Chilika Lake is a brackish water lake which retains the only sizable population of this rare dolphin in India, which is categorized as Vulnerable by IUCN. According to IUCN, direct mortality from fishing, habitat fragmentation and habitat destruction due to human intervention are some of the major threats faced by Irrawaddy dolphins.