watch out: Boats are a threat to the Chilika dolphins

Bhubaneswar, Feb. 5: The movement of mechanised boats in the Chilika lake appears to have pushed the Irrawaddy dolphins to the outer ring of the lagoon, a team of scientists from Japan and India has found.

More dolphins could be seen at the Magarmukh and New mouths of Chilika these days, the experts observed, adding that a more detailed picture would emerge after analysis of the data they had collected.

While watching the mammals in their natural habitat at Satpada remains high on tourists’ priority list, the experts say there have been some dolphin casualties due to the proliferation of boats.

In the past three years, collisions have killed 28 dolphins in the Chilika lake. Last year’s enumeration by the Chilika Development Authority (CDA) put the number of the endangered animals at 123.

“As many as 5,000 mechanised boats, used for both fishing and eco-tourism, frequent the waters of the Chilika lagoon,” said Sudhakar Kar, a wildlife research officer in the state forest department. “It is difficult for our enforcement officers to control the boats, their occupants often bullying the latter when confronted.”

Scores of boats ferry tourists from Satpada to the inside of the lagoon for sighting dolphins. While the CDA issues directives not to disturb the animals, the boats are often known to chase, circle and lead packs of dolphins to the cheers of tourists.

“The dolphin is an aquatic mammal with a highly developed sonar-like guidance system that can make it aware of the presence of a boat from a distance of 30 m,” said Rajendar Bahl, a professor at IIT Delhi and a member of the team. “Casualties occur when a dolphin is unable to avoid a speeding boat.”

The experts used an acoustics-based system to study the behaviour of dolphins from January 28 to February 3.

Apart from the wildlife wing of the forest department, IIT Delhi and CDA, the other institutions and agencies involved in the study are University of Tokyo and World Wildlife Fund.

“We will take some time to analyse the data and will present a detailed report later,” said T. Ura of University of Tokyo. The team will use a data logger to monitor dolphin traffic and migration pattern, he added.

Professor Ura, an expert at the underwater technology research centre of the university, said a “continuous monitoring system would be developed for observing the Irrawaddy dolphins in real time from a base centre set up at the CDA office in Satpada”.

The chief executive officer of CDA, Sudarshan Panda, said they have been trying to make boat owners instal propeller guards so that the vessels do not hit the animals.

The dolphin casualty this year, he pointed out, has been only three compared to 17 in 2004-05 and eight in 2005-06.

“We are trying to sensitise boat owners, fishermen and tourists on the safety of dolphins,” the CDA official said.