Fishermen smiled alongside officials from Cambodia's Fisheries Administration (CFA) as they held up the two-metre-long creatures -- weighing up to 130 kilograms (287 pounds) each -- before releasing them back into their river habitat.

The survival of the giant catfish -- one of the largest and rarest freshwater fish in the world -- underscores the urgent need to protect the river's free-flowing connectivity, a statement by the USAID-funded Wonders of the Mekong conservation group said.

Besides overfishing and plastic pollution, the Mekong River Basin has been degraded by upstream dams and climate change, which have had a major impact on water levels in the critically endangered catfish's aquatic home.

Its current population is unknown but is thought to have declined by around 80 percent over the last 13 years, according to the IUCN Red List.

Cambodia has placed tough restrictions on fishing in the vast river to try and reduce the number of endangered aquatic species killed in nets.

Numbers of Irrawaddy dolphins -- which once swam through much of the mighty Mekong -- have dwindled despite efforts to preserve them.

In 2022, Cambodian fishermen got a shock when they inadvertently hooked an endangered giant freshwater stingray four metres (13 feet) long and weighing 180 kilos.

Over the past 25 years, the CFA and researchers tagged and released around 100 giant catfish as part of a conservation program that encourages fishermen to report catches of rare species.

Conservationists said the recent giant catfish catches mark "a new era of conservation" and "new hope for the survival of a species that has become increasingly rare in much of its native habitat".