Bhubaneswar, Dec. 29: The increasing use of mechanised tourist boats as part of dolphin-viewing tours in the Chilka lake is proving to be the biggest threat to the endangered dolphins.

In recent years, following the promotion of tourism by the Orissa government, there has been a jump in the number of tourists visiting the lake. Most fishermen of Chilka’s Satpada and Balugaon fishing base turn tour operators during winter and carry large boatloads of tourists, who come to see the dolphins. As many as 11 dolphins have been killed between 2001 and 2002.

Two dolphins have been killed last month. There was hardly any dolphin casualty in the earlier years since the local fishermen do not catch or harm them. These deaths are being caused by mechanised tourist boats.

The boats, which are basically used for fishing, use Lombardini engines. These engines, unlike outboard motor ones, have long propellers, which jut out by as much as six feet from the rear of the boat.

As soon as the dolphins are sighted, the tourist boats surround them and move in. The animals panic, try to break out of the cordon, get injured by the propeller blades and finally dies of injuries. Unless immediate steps are taken to ensure sustainable tourism in the lake, these rare dolphins would be lost for ever.

The Wildlife Society of Orissa has suggested that the government should step in and persuade the boat operators with incentives or subsidies to replace their noisy and harmful Lombardini engine with outboard marine engines, which have short propellers.

Other proposals include self-regulation by the boatmen’s association to allow only a limited number of boats to leave in a batch for sighting dolphins. No boat should chase or come too close to a dolphin.

The forest department should also post a patrol boat during the tourist season to ensure that the dolphins are not chased, surrounded or killed.

This lake was recently recognised by the Ramsar Convention as a wetland of international importance since it possesses unique ecological features, including rare species of wildlife.

The Chilka lake has a tiny population of Irrawady river dolphins (Orcealla Brevirostris), estimated to range between 50 and 55 in number. They are mostly seen in the central sector and the outer channel close to the Satpada fishing base. This species of dolphin varies in length from 2 to 2.15 metre and is quite small, with a small beak and a rounded head. It has a very low rate of breeding since it produces a single baby after a gestation period of nine months.

These dolphins are Orissa’s unique natural heritage. They are extremely rare since there are only two places in the world where dolphins are found in a lake. Apart from the Chilka, the Songkhla Lake in Thailand is the only other lake where these rare mammals can be sighted.

But experts have observed sightings in the Songkhla are rare and the Chilika is unique since these animals are commonly sighted here everyday. In view of its endangered status, it has received the highest level of protection under law since it is included in Schedule I of the Indian Wildlife Protection Act, 1972. It is also included in Appendix II of the Convention on International Trade in Endangered Species.

Since complete biological details are not yet available about this rare species, it is listed as “insufficiently known” in the IUCN Red Data Book of endangered species of the world.