Species diversity and ecology of Tonle Sap Great Lake, Cambodia

Abstract

Tonle Sap Great Lake in Cambodia, the largest natural freshwater lake in southeast Asia, is situated within the floodplain of the Mekong River. Water levels in the lake vary by about 8 m between the dry season minimum and the wet season maximum when waters from the Mekong River back up the Tonle Sap River. The lake is highly productive – the annual fish catch from the Lake is estimated at between about 180,00–250,000 tonnes while the dai fishery on Tonle Sap River annually harvests about 12,000 tonnes of fish migrating from the lake to the Mekong River early in the dry season. At least 149 species of fish are recorded from the lake and it provides habitat for 11 globally threatened and 6 near-threatened species of vertebrates including globally important populations of Spot-billed Pelican, Greater Adjutant, Bengal Florican, Darter, Grey-headed Fish Eagle and Manchurian Reed Warbler. It also supports significant reptile populations including formerly Siamese Crocodiles, now hunted close to extinction, and probably the world’s largest harvest of freshwater snakes. The inundation area around the permanent lake is highly modified, with areas having been cleared for farming and settlements, and many semi-natural areas altered by burning, firewood and timber harvesting. Nevertheless some 200 species of higher plants have already been recorded. Threats to the lake include pressure through growth of the local population dependant on the lake for subsistence and livelihoods, overharvesting of fish and other aquatic species and potential changes in the hydrology of the River due to the construction and operation of dams which could reduce the amplitude of the lake flood cycle. However concerns that the lake is rapidly filling with sediment are unfounded.