Oil India`s seimic survey threatens rare dolphin
Oil India Ltd, a premier petroleum company of India, is planning to conduct seismic survey in total area of 4,500 sq km in eastern Assam consisting mainly of bed of river Brahmaputra and islands in the river. Such surveys are generally the first stage in oil exploration and they deploy an array of air guns and receiver equipments. The sound energy from the guns first moves down through the seabed. It then reflects back to the receiving equipment discontinuities in the underlying rock strata, such as oil and gas pockets. In the Brahmaputra river, this process threatens the Gangetic dolphin (Platanista gangetica), one of the most endangered species of dolphin.
The dolphin is a cetacean species. Experts have pointed out that seismic surveys affect such animals in different ways: it damages their body tissues (often causing death) and ears. They point out that the reduction in auditory sensitivity is very often permanent.
The surveys disturb the cetacean's communication signals, particularly those associated with tracking prey or avoiding predators. The animal also finds it difficult to recognise human threats and cannot avoid boats or other water faring vessels. All this disrupt the animal's normal behaviour (it avoids a particular area, its respiratory patterns alter, so do its diving patterns), causing it substantial stress and rendering it vulnerable to disease. The animal's movement away from its habitat also reduces its prey base.
The blind creature The Gangetic dolphin's habitat (the Brahmaputra River) is narrow and shallow. Given this constricted environment, the dolphins might find it difficult to avoid explosions and airguns used in the survey.
This author's survey indicates an encounter rate of 0.18 dolphins per km or one dolphin per 5.4 km. We know that dolphins in the Yangtze river in China have been killed by explosions along the river banks and in shallow water; their counterparts in the Brahmaputra might suffer the same fate if explosives are used for the Oil India survey.
Driven downstream Moreover, noise, disturbance and activity around the seismic survey could drive the dolphins downstream, thereby displacing them from a large part of their feeding and breeding habitat. Research in the Mahakam river in Indonesia has showed that slow moving tugboats that produce low frequency noise of high energy changed the migration route of Irrawaddy dolphins. The creatures avoided the boats.
Prolonged exposure to underwater noise could cause hearing damage and also interfere with the dolphins sonar causing it substantial stress. All these assume even more significance because the Gangetic dolphin is a blind cetacean species. It depends on echolocation (the production of sound pulse, similar to sonar) to navigate, communicate and to find food. Seismic surveys which also involve emission of sound pulses can disturb this function.
There is of course an argument that much of the noise generated by the seismic pulses is that of a different frequency than those produced by the dolphin. But without a proper understanding of the proposed survey methods and their subsequent evaluation by a group of dolphin acoustic specialist, the exact impact of the Brahmaputra survey is unknown territory.
Where are the experts The environmental impact assessment (eia) study on this aspect was conducted by a team of experts of Guwahati University, Assam. However, the team had no dolphin experts. So, during the public hearing meeting on October 30, 2006, on this issue, which was organised by Pollution Control Board, Assam, we requested Oil India to initiate a detailed investigation on the possible impacts of seismic survey on the dolphins of Brahmaputra river.
We have requested that this investigation should be carried out by a team of dolphin and bio-acoustic experts and that the seismic survey is suspended till then. Our campaign has also drawn the attention of cetacean experts and conservation organisations worldwide including iucn - ssc, International Whaling Commission, Whale and Dolphin Conservation Society. These bodies have requested the concerned Indian governmental authorities to treat the matter as urgent and they have shown some interest in the matter.
We are awaiting the final decision of these authorities.
Abdul Wakid is programme leader, Gangetic Dolphin Research and Conservation Programme, Aaranyak, Samanwoy Path Survey, Guwahati, Assam