Chilika Lagoon IMMA

Criterion A – Species or Population Vulnerability

Irrawaddy dolphins are listed as globally Endangered and decreasing by the IUCN Red List of Threatened Species (Minton et al. 2018). The estimated population in this IMMA is small at 112-140 (Sutaria, 2009). The population in Chilika is also resident based on photo-identification data from 2004 to 2010, making Chilika an important area for this species. In Chilika, Irrawaddy dolphins live in close proximity with intense fishing activities and mortality rates reached as high as 7% (Pattanaik et al 2007, Sutaria 2009, D’Lima 2014), primarily from fisheries entanglements. Such high mortality rates makes the population vulnerable to stochastic and anthropogenic pressures (Sutaria 2009). Habitat loss from the accumulation of silt is one of the major pressures on this brackish water system.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Chilika supports a small population of resident Irrawaddy dolphins, physically isolated from coastal populations, vulnerable to fisheries entanglements, un-managed dolphin watching tourism traffic and habitat loss. Given that the population is resident, and spends its entire lifecycle within the lagoon, Chilika is an area that is additionally important for breeding and calving. Mating chases were observed where the chased individual was seen belly-up with other individuals on top (Sutaria 2009). The Outer channel of the lagoon had a higher density of mother-calf pairs and juvenile than the rest of the lagoon, and new- born calves showing foetal curves were also sighted with adults (Sutaria 2009, D’Lima 2014). Mark-Recapture analysis of 80 photo-identified individual dolphins using natural marks estimated the abundance of the population as 109 to 112 individuals at CV=0.07 (closed models); and 140 at CV=0.25 (open models), based on surveys from November 2004 to December 2006 (Sutaria 2009). Their area of space use is not more than 400 km²  with individual home-ranges as small as 1.7 km²  showing how sensitive the population cold be to changes in habitat features such as depth and salinity. The lagoon is highly productive, providing a rich source of prey to the dolphins. Multiple foraging strategies – both solitary and cooperative group foraging have been observed in Chilika (Sutaria 2009, D’Lima 2014). Coastal surveys of Orissa have not sighted another such resident population (Sutaria 2009, Orissa State Forest Department) making the population in Chilika an important source population for the species in India and regionally. The closest Irrawaddy dolphin sightings outside Chilika, are upstream in the mangroves of Bhitarkanika, 250-300km north of Chilika.The IUCN Red List of Threatened Species lists all other isolated and semi-isolated populations of Irrawaddy dolphins in the species’ range as Critically Endangered.