River dolphin population stable, says report Prabal Kr Das GUWAHATI, Nov 1 A recent report on the status of Ganges river dolphins (Plantanista Gangetica Gangetica) in the Brahmaputra and adjoining rivers has suggested that after a long period of decline, the population of the endangered species could have stabilised. Striking a cautionary note, the report submitted to the Sir Peter Scott Fund of the IUCN, however, underlines the need to strengthen conservation measures for the survival of the species.
The report produced by Abdul Wakid of Aaranyak and Gill Braulik of Sea Mammal Research Unit, University of St Andrews, Scotland, has mentioned a population of around 264, located in the Brahmaputra, Kulsi and Subansiri rivers. The stretch of the Brahmaputra between the Assam-Arunachal border and Dhubri was found to contain 80.3 per cent of the cetaceans, 11 per cent located in the Kulsi, and the remaining 8.7 per cent recorded in the Subansiri.
Compared to other sections in the Brahmaputra, the stretch between Dhansirimukh and Tezpur provided more encounters with river dolphins. It could be due to better protection measures provided by the Kaziranga National Park, which lies in close proximity.
A comparison of the data with findings of a previous survey carried out in 2005 showed that the population estimate was roughly the same, Abdul Wakid told The Assam Tribune. The earlier estimation carried out by Wakid and his team had recorded about 250 river dolphins in water bodies of the Brahmaputra valley.
The report submitted this year mentions that one of the reasons for the population becoming stable could be due to spread of public awareness. A series of campaigns have been targeted at riverine communities and fishermen to protect the endangered species in parts of the Brahmaputra valley by NGOs.
A number of threats, however, persist for the river dolphins, which were once plentiful in the Brahmaputra and a few of its tributaries. Accidental killing through fisheries by-catch is thought to be the major threat for the species in the Brahmaputra, the report observes. Of the 16 deaths documented in 2008, 12 were attributed to accidental killing.
Significantly, investigations revealed that though some deaths caused by gill net entanglement were labelled as accidental, most cases were intentional. During pre-monsoon and monsoon period, fishermen use gill nets on the migratory paths of rivers to kill river dolphins for their oil which fetches high prices. As the killings take place in remote areas, prosecution is nearly impossible. The silver lining for the species is most of their habitat continues to be free from pollution.
For the population in the Subansiri, a grave threat has been identified in the form of a dam to be constructed at Gerukamukh by the National Hydro Power Corporation. The construction of this dam on the river will directly affect the dolphin population of the river changing the whole eco system, the report states.
Referring to the population in Kulsi, the report says that sand mining could be perceived as a disturbance to the species, but at the same time effects such as deepening of the stream could have positive impact on the habitat. More detailed studies were required to ascertain the facts on the basis of good science.
The project was conducted with a mix of established and new techniques, and included extensive ground observation, satellite imagery and GIS.
