Researchers are looking into why 25 dolphins went missing for no apparent reason as the overall population continues to drop. The total population is estimated to be 89.
World Wildlife Fund (WWF) Cambodia country director Teak Seng said conservationists and researchers are concerned.
The 25 were recorded last year, but now researchers cannot locate them and are unsure if they have migrated.
According to a joint report by the WWF and the Fisheries Administration under the Ministry of Agriculture, Forestry and Fisheries, the number of Irrawaddy dolphins is analysed and compiled every two or three years.
In 2017, the number of dolphins was estimated to be 92. The number today is around 89, not accounting for the missing 25.
From 2007 to 2020 the average annual growth rate has been 1.02 per cent and the average annual death rate has been 2.14 per cent, according to the report.
“Previously, dolphins in Cambodia existed in large numbers,” Seng said.
In 2018, the research team logged nine dolphin births and four deaths. Last year, they recorded 13 births and eight deaths. So far this year, they’ve chalked up six births and five deaths.
Seng said the Fisheries Administration and partner organisations are monitoring the migration of dolphins.
He said it is the first time dolphins might have migrated somewhere else and the institutions are researching the reason.
“They can migrate to small rivers because we study them only on the Mekong River,” Seng said.
According to the joint press release, the number of freshwater dolphins in Asia has sharply declined and dolphins have been placed on the International Union for Conservation of Nature (IUCN) Red List.
Phay Somany, the deputy director of the WWF’s department of Fisheries Conservation and Government Liaison, said on Thursday that in the mid-1970s, thousands of Irrawaddy dolphins scattered along three tributaries of the Mekong River and the Tonle Sap River. Today they live along the Mekong about 180km from the Anlong Kampi zone in Kratie province to the Khone Falls in Laos bordering Cambodia’s Stung Treng province.
“During our research this year we failed to see 25 dolphins we identified last year. The Mekong River water level is very low. It makes some dolphins unable to live in their canyons,” he said.
Somany said the failure to find the dolphins can be attributed to downstream migration.
Vong Savoeun, the Stung Treng provincial Fisheries Administration chief, said dolphin migration is not just a factor of nature.
As an example, he said people have used nets mixed with batteries and it makes the river unliveable.
“They have to migrate to other places.”
He said the sounds of large motorboats and racing boots in the Anlong dolphin conservation area might also be a reason for the dolphins to migrate.