Touch Seang Tana, Cambodia's chairman of a commission for conservation and development of the Mekong River Dolphin and eco-tourism, told Kyodo News the report by the World Wide Fund for Nature was aimed at attracting and convincing donors to inject more funds into the group.

Inhabiting a 190-kilometer stretch of the river, the Irrawaddy dolphin population has suffered 88 deaths since 2003, of which 58 were calves under 2 weeks old, bringing the latest population to an estimated 64 to 76 members, the WWF said in its report.

WWF researchers found toxic levels of pesticides such as DDT and environmental contaminants such as PCBs in an analysis of 21 dead dolphins retrieved between 2004 and 2006, as well as high mercury levels in some of them, the group said.

Touch Seang Tana said the number of dolphins has increased from roughly 120 recorded in 2000 to about 160 in 2009.

"There are no such critical pollutants, otherwise, some 50,000 people living along the 200-km stretch of the river and who are using and drinking the water might have died before the dolphins," he said.

He also disputed the number of dolphin deaths recorded by the WWF, suggesting the group should have recorded as many as 118 deaths since 2000 due to illegal fishing and a lack of conservation activities until after 2003.