PHNOM PENH, April 23 (Xinhua) -- The population of critically endangered river dolphins in the Mekong River in Cambodia has risen from 80 to 92 in the past two years, the first increase since records began more than 20 years ago, said a new census result released on Monday.

The census was conducted by the World Wildlife Fund (WWF) and the Cambodian government, said a WWF statement.

The statement said effective river patrolling by teams of river guards and strict confiscation of illegal gillnets, which accidentally trapped and drowned dolphins, were the main reasons for this historic increase.

"After years of hard work, we finally have reason to believe that these iconic dolphins can be protected against extinction -- thanks to the combined efforts of the government, WWF, the tourism industry and local communities," said Seng Teak, country director of WWF-Cambodia.

"The tour boat operators are the secret ingredient in this success story as they work closely with law enforcement to report poaching and help confiscate illegal gillnets," he said.

The statement said the first official census in 1997 estimated that there were 200 Irrawaddy dolphins in the Mekong, a figure that fell steadily due to bycatch and habitat loss until there were only 80 left in 2015. But now the decline appears to be on the mend.

According to the statement, the surveys also pointed toward encouraging signs for the long-term health of the population with an improvement in the survival rate of dolphins into adulthood, an increase in the number of calves and a drop in overall deaths.

It said two dolphins died in 2017 compared with nine in 2015, while nine new calves brought the number of dolphins born in the past three years to 32.

"River dolphins are indicators of the health of the Mekong River and their recovery is a hopeful sign for the river and the millions of people who depend on it," said Teak.

Eng Cheasan, director-general of Cambodia's Fisheries Administration, said the Mekong dolphin was considered Cambodia's living national treasure and the results of this census reflected many years of continuous efforts to protect this species.

"We will continue our conservation efforts to rebuild its population by eliminating all threats to the survival of this species," he said.

The surveys covered 190 km of the main channel of the Mekong River in eastern Kratie and northern Stung Treng provinces, the statement said, adding that the surveys were done in both directions with teams photographing dolphins and comparing the distinctive marks on their backs and dorsal fins against a database of known dolphins.

The Mekong River Irrawaddy dolphins have been listed as critically endangered on the World Conservation Union Red List of Threatened Species since 2004.