Environmentalists gathered in Cambodia today (Wednesday) to release four endangered giant catfish into the Mekong River.
The giant catfish, which is indigenous to the Mekong and its tributaries, is the world's largest freshwater fish. It can grow as long as three meters and weigh up to 300 kilograms.
The Mekong catfish has been listed as critically endangered by several international conservation groups, who say overfishing and dam building have disrupted its natural habitats.
Only five or 10 of the giant fish are caught in the Mekong each year.
The fish released today (Wednesday) had been raised in captivity for seven years by a Cambodian fisherman. They have been fitted with tags in case they are caught by fishermen.