The WWF has expressed regret over the death of the last known river dolphin in the transboundary pool in the Mekong between Laos and Cambodia.
The World Wildlife Foundation said "this death most likely represents a national-level extinction of this freshwater dolphin species in Laos".
It said that a 25-year-old old male dolphin was found dead at Koh La Ngo. The dolphin weighed 110 kilogrammes and was 260 cm in length. "He is believed to have been dead for about three days," it said.
WWF Asia-Pacific Director Lan Mercado said the Mekong river dolphin population in the pool had declined over the past few years "due to multiple threats, including hydro-power dam construction causing disruptions to river flow and reduced fish abundance".
He also blamed overfishing, the use of gill-nets, and other damaging fishing practices such as electrofishing. The WWF said the population was declared "functionally extinct in 2016, when only three dolphins were left".
"There were an estimated 89 river dolphins left in the Cambodian part of the Mekong river according to surveys conducted in 2020," WWF said. The news was posted at wwf.org on Thursday.
"Successful collaboration and sustained conservation action with the government, fishers and communities in Cambodia has helped to reduce bycatch and strengthen habitats," Mr Mercado said. "The remaining population of 'critically endangered' river dolphins in the Cambodia section of the Mekong is now stable.
"This latest river dolphin death highlights how vulnerable these and other species remain," he added. "Documenting the lessons learnt from this tragic loss is critically important if we are to protect the endangered species in the region."