Net Gains

Team members: Coralie D'Lima, Anindya Sinha & Rohan Arthur

Project timeline: 2004 to 2007

In India, the Irrawaddy dolphin is  restricted to Chilika Lake in Orissa.  The dolphin shares a unique relationship with local fishers who believe the dolphin is critical to their fisheries. Our work uses behavioural  and socio-economic approaches to understand this relationship.

The Irrawaddy dolphin (Orcaella brevirostris) often compete with fishers for fish, occasionally getting trapped in nets as a result. In some instances however, the Irrawaddy dolphin has developed a seemingly mutualistic relationship with fishing communities in the form of cooperative fishing. Detailed reports of this behaviour have been published for the Irrawaddy dolphin population in Myanmar. At Chilika lagoon, presumed co-operation has been observed between fishers and dolphins. Traditional fishers see the Irrawaddy dolphin as linked inextricably with their fishing activities, and talk of a time when they could call out to the dolphins, to drive fish into their nets. 

However, the importance of this mutualism to the behaviour, life and survival of the Irrawaddy dolphin at Chilika lagoon however, remains unclear. The aim of this study was to analyse human-Irrawaddy dolphin interactions with a special focus on how foraging behaviour is affected by fishing in Chilika lagoon. The specific objectives of this study are to study the foraging behaviour of the Irrawaddy dolphin at Chilika lagoon, along with the dependence of the dolphin on co-operative forging with fishermen, to investigate the significance of dolphins to the fishers, and to analyse the attitudes and perceptions of local fishers towards the Irrawaddy dolphin and its conservation.

Our work is showing that the benefits that fishers perceive have strong roots in cultural traditions.  Fishers see the dolphin as an important totem, a goddess incarnation sent to them to help them fish.  Behavioural observations showed that dolphins employ a range of feeding techniques in the lagoon including very complex group foraging behaviours.  However, many dolphins dedicate a large part of their time feeding at nets, if not from them.  We have also documented them using a curious 'spitting' behaviour which they use to herd fish towards nets.  Fishers perceive this herding as a form of cooperative fishing and believe it helps boost their catch.  Our observations partially confirm these beliefs - while fish catch does not necessarily increase when dolphins feed at nets, the composition of the catch is markedly different, increasing the economic value of the catch for fishers. When dolphins forage at nets, the catch is dominated by mullets, which, apart from being economically important, is also a fish that local fishers prefer.  Our studies are showing that this cooperative fishing between fishers and dolphins is based on a  complex interplay of behaviour, economics and culture.