Shark attacks on Irrawaddy dolphin in Chilika lagoon, India

Irrawaddy dolphin Orcaella brevirostris Gray, 1866 inhabit Chilika lagoon, Odisha on the east coast of India. The narrow outer channel connecting the main lagoon and the Bay of Bengal harbour approximately 60% of the Irrawaddy dolphin population. The bull shark Carcharhinus leucas Muller and Henle, 1839 travels from the sea 5-10 km inward to the outer channel during late gestation period.Mortality of Irrawaddy dolphins related to bull shark attack ranged from 1 to 3% of the population. An account of the shark attack on Irrawaddy dolphin was first recorded on 24th April, 2003 from the Chilika lagoon. Salinity and depth parameters of the outer channel are conducive for both the shark and the dolphin show the overlapping of the habitat. This study indicates that habitat or prey overlap may be responsible for the fatal bull shark attacks on Irrawaddy dolphin in Chilika lagoon.