Cambodian Prime Minister Hun Sen on Monday ordered the creation of endangered dolphin protection zones on the Mekong, after the death of three of these mammals caused by fishing lines and nets in December.

Endangered Irrawaddy dolphins, known for their domed foreheads and short snouts, once swam much of this river, but in recent decades their range has been restricted to a stretch of 190 km between the north-east of the Cambodian province of Kratie and the Laos border.

Their population has been in steady decline since their first census in 1997, when 200 were counted compared to the current 90, a decline attributed to habitat loss and destructive fishing practices.

Three of these breeding-age animals died in a week last month, alarming conservationists, who have called for day and night patrols to protect the dolphins from illegal fishing.

During a ceremony in Kratie, Hun Sen ordered authorities to install buoys around designated protection zones, in which there will be an "absolute ban" on fishing.

"The Mekong, home to dolphins and nearly extinct fish species, needs to be well managed so that dolphins don't die entangled in gillnets," he said, referring to those nets set up by fishermen on some parts of the river to catch fish.

"The areas reserved for dolphins must be completely protected," he added, adding that the presence of these mammals contributes to local tourism.

Eleven of them died in 2022, bringing the total number of dolphins that have died in the past three years to 29, according to the World Wide Fund for Nature (WWF).

In a statement, WWF called on all relevant authorities to “promulgate and deploy appropriate measures to urgently address the mortality” caused by gillnets and electrofishing used in dolphin conservation areas.

Cambodia is home to the largest population of Irrawaddy dolphins, which are also found in rivers and lakes in Burma, Indonesia, India and Thailand.