Cambodian fishermen on the Mekong River got a shock when they inadvertently hooked an endangered giant freshwater stingray four meters long and weighing 180 kilos, scientists said on Wednesday.

The female leviathan, one of Southeast Asia's largest and rarest species of fish, was caught by accident last week in Stung Treng Province when it swallowed a smaller fish that had taken a baited hook

An international team of experts who doing research there worked with the fishermen to unhook the ray before weighing and measuring it and returning it unharmed to the river.

The giant Mekong is a crucial habitat for a vast array of species large and small. According to Zeb Hogan, a fish biologist from the University of Nevada, said the river's underwater ecosystem was poorly understood.

The study group said in the statement that the remote location where the ray was caught has pools up to 80 meters deep and could harbor even bigger specimens. But they also warned that underwater video footage showed plastic waste even in the deepest stretches of the Mekong, along with "ghost nets" -- abandoned by fishers but still able to snare fish. 

Listed as endangered by IUCN, the giant freshwater stingrays are threatened by heavy fishing, habitat degradation and fragmentation.

(Cover image via screenshot)

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