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Irrawaddy dolphin numbers take a dive

Written by Porter Barron
The Phnom Penh Post. Friday, 27 June 2008
http://www.phnompenhpost.com/index.php/200806268844/National-news/Irrawaddy-dolphin-numbers-take-a-dive.html

The most recent population survey of Cambodia’s Irrawaddy dolphins
shows the dwindling species – its youngest generation in particular –
remains imperiled.

After almost 140 hours of dolphin-spotting on the Mekong River from
Kratie to the Lao border, researchers estimate 71 dolphins survive,
although the population could range from 66 to 86, according to the
global conservation group WWF.

The survey – carried out during the dry months of April and May 2007,
when the river level drops and the dolphins are concentrated in nine
deep pools – counted markedly fewer specimens than a 2005 study that
estimated a population of 108 to 146.

Both high mortality and a new, more accurate survey methodology could
account for the drop-off, according to Richard Zanre, WWF’s Freshwater
Conservation Program Manager.

“The good news is adult mortality has reduced over the last five or
six years,” Zanre said.

He credited government and NGO efforts to curb the use of gill nets in
the core habitat, including an official ban instituted last year and
alternative livelihood programs for fishermen in the area.

The nets are believed to have snared and drowned a significant number
of the nearly 80 dolphins found dead in the past five years.

“But the big concern is the calf mortality remaining high,” Zanre
added. “We are also seeing what seems to be a drop in the birth
rate.”

The exact cause remains a troubling unknown. Results from autopsies
conducted on the tissue of dead calves have recently returned from
laboratories in Canada and the US. They await analysis.

Additionally, tests will be run on water samples to learn whether
sewage, agricultural or industrial run-off could be hindering
reproduction.

Another threat looms upstream, where the Lao government recently
approved construction of a hydroelectric dam above the Khone Falls on
the Laos-Cambodia border, Zanre said.

Cambodia’s Irrawaddy dolphins, which range from Kratie to Southern
Laos, are one of only three populations still in existence. The others
survive in Myanmar and Indonesia.

The International Union for the Conservation of Nature has listed
Cambodia’s dolphins as Critically Endangered since 2004.

 
 

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