The maximum volume of Mekong catfish reaches 300 kg, while the maximum length of freshwater rays is up to 5 m. The Mekong River, with hundreds of abundant fish and sediment sources, is the lifeline of tens of millions of people.

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With a length of up to 3.2 m and a volume of up to 300 kg, catfish is one of the largest freshwater fish species in the world. However, they are facing the highest risk of extinction among the Mekong fish species. Photo: lugaluda.com.

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Tra fish live in the lower Mekong River in Vietnam, Laos, Cambodia and Thailand. The number of them has dropped sharply in recent years because of overfishing, the occurrence of hydroelectric dams and destruction of habitats. Photo: National Geographic.

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As one of the world's largest freshwater fish species, the Mekong stingray body can reach a length of 5 m and weigh up to 30 kg. However, at present no one knows how many freshwater stingrays live in the Mekong River and whether they can live in the sea like saltwater drowns. Photo: AP.

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The scientific community knows only one thing: The number of freshwater river stingrays in the Mekong River is decreasing very rapidly in the last few decades due to their degraded habitat. Photo: National Geographic.

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Giant carp of the Mekong River is one of the largest carp species in the world. Their maximum body length and weight can reach 2.4 m and 250 kg. Photo: hubpages.com.

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Giant Thai carp (also known as copy Siam, black copy) is also a large-sized carp of the Mekong River. Most of them are over 1.5 m long and more than 45 kg in weight. The length and weight of the largest ones can be up to 3 m and 300 kg. Thai carp meat is very tasty and that is the reason why their number is reduced by overfishing. Photo: National Geographic

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In Vietnam, Thai carp is called coral fish. In addition, they are also known as "king fish" of the Western river water. Photo: answers.com.

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Flagfish (Thai called Pla Thepa fish) can reach a mass of 200 kg, while their maximum body length is 3 m. Photo: waterwolves.com.

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A pawns in the Mekong River. Photo: aquatic-photography.com.