Ganges River Dolphin Survival Threatened by Oil Exploration

Such prospecting "has potentially disastrous implications for Ganges River dolphins," the report concludes.

Estimates have put the total population of the Ganges River dolphin, Platanista gangetica gangetica, at around 2,000. Between 240 to 300 of these inhabit the Brahmaputra River system in India, according to the survey prepared for the International Union for the Conservation of Nature's Sir Peter Scott Fund.

Ganges River dolphin (Photo courtesy Abdul Wakid)

"Our research shows accidental killing through fisheries bycatch, followed by poaching for oil, are the major threats to the dolphins of the Brahmaputra river system," said project leader Abdul Wakid, Ph.D., who conducted the research with Gill Braulik of the University of St. Andrews' Sea Mammal Research Unit.

"Their habitat is also being degraded by human activities," said Wakid. "Dam building and a proposed seismsic survey in the Brahmaputra river are potential threats."

The Ganges River Dolphin is found mainly in the Ganges and Brahmaputra river systems in India and Bangladesh.

According to older Assam residents, 30 years ago, the Gangetic dolphin was one of the most commonly sighted large aquatic animals in the Brahmaputra River system. But, due to increasing pressure from human activities, the overall population of the species has been declining and these dolphins have been extirpated from most of the major tributaries of the Brahmaputra and are now restricted to pockets in the Brahmaputra mainstream.

This survey concentrated on the 1,044 kilometer stretch of dolphin-inhabited Brahmaputra River system, primarily in the state of Assam in northeast India. In a 2005 survey of the same river stretch by the same investigating group a best estimate of 250 dolphins was recorded.

The project, funded by Fondation Ensemble, was designed to provide missing baseline information on distribution, abundance, behavior and acoustics of Ganges River dolphins in the Brahmaputra River and suggest suitable locations to establish protected areas.

The project took place from October 2007 to September 2008. Project workers carried out 32 awareness campaigns along the Brahmaputra valley, focusing on fishing communities in areas surrounding dolphin hotspots.

Ganges River dolphin awareness campaign with Assam children (Photo courtesy Abdul Wakid)

The vessel-based dolphin survey was conducted from February-April, 2008 as this is the period of minimum river discharge when dolphins are easiest to count.

The study identified eight river sections as potential protected areas and community-based dolphin conservation as the best strategy to save the dolphins.

Based on high abundance of dolphins, potential for protection and possibilities for dolphin ecotourism, eight sections of the river were identified as potential protected areas and community-based conservation areas.

"The Brahmaputra River is very important habitat for these endangered dolphins," said Braulik, who is a member of the IUCN’s Cetacean Specialist Group. "To protect them it is vital that we involve local river communities."

"In some places, like in the Kukurmara area of Kulsi River, for example, the dolphins are a tourist attraction due to protection by local communities. But in other areas, dolphins are accidentally killed in fishing nets or are sometimes deliberately caught and killed for their oil," Braulik said.

The small-mesh fishing nets are also a threat to dolphins because they remove from the river large numbers of the fish that dolphins prey upon.

Extensive use of various types of gill nets in the Brahmaputra River over the last 15 years has resulted in the sharp decline of fish fauna and has likely reduced the amount of dolphin prey, the report states.

"Although fishing using very small mesh-sized gill nets (current jal) is banned in Assam from 1st May to 15th July, we observed this banned activity throughout the year," the researchers state.

"Lack of proper management attention to this important issue," says the report, "has resulted in a severe increase in anthropogenic pressure on fish fauna in the Brahmaputra river system, which in turn affects the dolphins through food shortage and habitat disturbance."

Copyright Environment News Service, ENS, 2009. All rights reserved.