GUWAHATI, April 21? The population of river dolphins (locally called sihu or sisu) a highly endangered aquatic mammal is declining alarmingly. The 2002 river dolphin census carried out by the Dolphin Conservation Society (DCS) with support from the WWF-India, has recorded only 198 dolphins in the Brahmaputra river, with 89 adults, 60 adolescents and 49 calves. The previous census in 1997 had counted 218 dolphins. The chairman of the DCS, Sri Sujit P Bairagi, told The Assam Tribune that depletion of the dolphin population in the Brahmaputra was primarily due to large-scale poaching for its oil and accidental killings through entanglement in under-water gillnets, and secondarily due to loss of habitat. However, potentiality of these threats are river and area specific. In the Brahmaputra, intentional killings for its oil is the major cause, especially in the lower stretches of the river bordering Bangladesh. Dolphin oil has got several uses and the most important one being its use as fishing bait. Besides, it is also supposed to have some medicinal value, he said. Again, increased silt deposition due to erosion in upper stretches which form huge sandbars is affecting dolphin habitat by decreasing the depth of the river. Over exploitation of fishery resources also reduces the abundance of food fish in the entire stretches, he added.
Unlike the Ganges, Sri Bairagi said, the Brahmaputra is not experiencing significant water pollution and hence chemical hazards are comparatively less though pollution by some agricultural pesticides is on the rise. Again, in the Brahmaputra, the environmental consequences of water development are yet to be ascertained as there is not any major dam constructed in the main drainage and hence till this moment the dolphins are safe from population fragmentation and other ecological complexities. ?But the recent trend of sanctioning hydel projects in the North east without proper Environment Impact Assessment (EIA) may be a cause of concern for the dolphins? future?, he warned. Underscoring the need to have a programme like ?Project Dolphin? on the line of the Project Tiger to protect the endangered species, Sri Bairagi said that the dolphin population in the Kulsi river was almost on the verge of extinction due to ecological degradation of the river. In 1993, there were 25 dolphins but now it has only 11. Citing river-bed sand extraction as the main reason of behind this, he said the DCS had urged the State Government umpteen times to stop all sorts of human interference in the river and also to declare a part of it a ?Dolphin Sanctuary?. It may be mentioned that the Government had leased out that particular part of the river for sand extraction 10 years back.