Mekong - Natural History

Natural History

The Mekong basin is one of the richest areas of biodiversity in the world. Only the Amazon boasts a higher level of biodiversity. Biota estimates for the Greater Mekong Subregion (GMS) include 20,000 plant species, 430 mammals, 1,200 birds, 800 reptiles and amphibians and an estimated 850 fish species. In 2009, 145 new species were described from the Mekong Region, comprising 29 fish species previously unknown to science, two new bird species, ten reptiles, five mammals, 96 plants and six new amphibians. The Mekong Region contains 16 WWF Global 200 ecoregions, the greatest concentration of ecoregions in mainland Asia.

No other river is home to so many species of very large fish. The biggest include the giant river carp (Probarbus jullieni), which can grow up to 1.5 metres (4 ft 11 in) and weigh 70 kilograms (150 lb), the Mekong Freshwater Stingray (Himantura chaophraya), which can have a wingspan of up to 4.3 metres (14 ft), the giant pangasius (Pangasius sanitwongsei), Siamese giant carp (Catlocarpio siamensis) and the endemic Mekong giant catfish (Pangasianodon gigas), all three of which can grow up to about 3 metres (9 ft 10 in) in length and weigh 300 kilograms (660 lb). All of these are in serious decline, because of dams, flood control and overfishing.

One species of freshwater dolphin, the Irrawaddy Dolphin (Orcaella brevirostris), was once common in the whole of the Lower Mekong but is now very rare.

Among other wetland mammals that have been living in and around the river are the smooth-coated otter (Lutra perspicillata) and fishing cat (Felis viverrina).

The endangered Siamese crocodile (Crocodylus siamensis) occurs in small isolated pockets within the northern Cambodian and Laotian portions of the Mekong River. The Saltwater crocodile (Crocodylus porosus) once ranged from the Mekong Delta up the river into Tonle Sap and beyond but is now extinct in the river, along with being extinct in all of Vietnam and possibly even Cambodia.