The Giant pangasius catfish now has protection against fishing in Cambodia.
Pangasius gigas, which is the world's largest freshwater fish species, can reach over 3m/10' in length and was found through much of the Mekong basin.
However, overfishing has reduced populations to just 95-99% of what they were and experts now believe there are only a few hundred left.
Now Cambodian fishermen must hand over any Giant pangasius they catch to the Mekong Fish Conservation Project so they can tag and re-release the endangered fish elsewhere.
Zeb Hogan, who works for the World Wildlife Fund and heads the Mekong Fish Conservation Project, told National Geographic that the Cambodian Department of Fisheries had designated a massive fishing area at Tonle Sap a special research and conservation area, which means any endangered fish caught there should be safe.
Hogan said: "What that means is that the fishermen are obligated to provide endangered species that they catch to us free of charge for tagging and release."These fish are on the verge of extinction, and that's a warning to us that there's something wrong with the river system...""The largest migratory fish are usually the first to disappear, but they won't be the last."
Tonle Sap is an area of Cambodia in which a massive row of 14 nets are positioned in the river, one every kilometre. One of the nets at the southern part of the series has a cone-shaped collecting part and has caught a number of the Mekong's giant fish species.