Since 2003, there were 88 deaths registered, 60 percent of which were calves under two weeks old and the population of Irrawaddy dolphins is now estimated at between 64 and 76 individuals. inhabiting a 190km stretch of the Mekong River between Cambodia and Lao PDR after.
A necropsy showed toxic levels of pesticides such as DDT and environmental contaminants such as PCBs. The dolphin’s immune systems were suppressed by these environmental contaminants, which turned an otherwise manageable bacterial disease deadly. These pollutants may also pose a health risk to human populations living along the Mekong that consume the same fish and water as the dolphins.
Additionally, there were high levels of mercury found in some of the dead dolphins. This mercury could possibly derive from gold mining activities and directly affects the immune system making the animals more susceptible to infectious disease.
Another factor in the dolphins death was the limited genetic diversity due to inbreeding.
The Mekong River Irrawaddy dolphin has been listed as critically endangered on the IUCN Red List of Threatened Species since 2004.
WWF Cambodia is currently investigating the source of the environmental contaminants as well as thinking of a trans-boundary preventative health program to manage the disease affected animals in order to reduce the number of deaths each year. “Science has shown that if the habitat of cetaceans is protected then populations can show remarkable resilience.” said Seng Teak, Country Director of WWF Cambodia.
Materials from WWF International.
Copyright © 2009 by Marine Science Today, a publication of OceanLines LLC