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 Stung Treng, Cambodia
Site description

Stung Treng is located in the upper Cambodian reaches of the Lower Mekong River. Declared as a Ramsar site in 1999, the site extends 37 km along the Mekong River from 6 km north of Stung Treng town to 3 km south of the Lao boarder. The site encompasses the entire Mekong River, its islands and channels, to the terrestrial boundary 150 metres to the landward side of the riverbanks. In some areas the river is very broad with numerous channels between rocky and sandy islands. In others, the river forms a single channel with fast flowing current. Seasonal variation in water height is up to 10 metres. In the dry season rapids can be seen where bedrock is close to the surface.

There are 10,000 people living within, or close to the site boundaries. This number is expected to increase with the improved security situation in this remote part of Cambodia. Three of the islands within the Ramsar site are permanently populated with established villages. In the dry season, larger islands are used for agriculture, harvesting of natural resource and hunting.

A unique seasonally inundated riverine forest habitat, which has yet to be described, is a globally significant feature of this site. This forest is found in the flowing water on the edges of islands and rivers and on rocky outcrops and is described in more detail below. This stretch of the Mekong is important for the migration of over 100 species of fish between Lake Tonle Sap and the upper reaches of the Mekong above Khone Falls. The site and its immediate tributaries is also an important breeding site for fish species that can not migrate beyond the Khone Falls and may be an important habitat for fish breeding and offer shelter for fish during period of peak flow. By law, commercial fishing lots are not allowed to operate in Stung Treng Province.

The main habitats within the Stung Treng Ramsar site include:
Riverine inundated forest growing on the sandy and rocky islands comprising tree species identified tentatively as Barringtonia sp., Eugenia sp., and Arcacia sp.. Visually strange, the trunks of these trees are mostly bent almost horizontal in the direction of the river flow with branches and leaves swept in the same direction (giving the appearance of being swept away). In some cases trees are supported by large buttress roots (1-2m. high) protruding downstream to support the trunks against the current. Many of the trees have reduced, narrow leaves reminiscent of rheophyllic trees and there are many epiphytes or parasites particularly of the fig Ficus sp..
River channels run the length of the site. The bottom substrates include alluvial deposits, varying from fine mud to larger pebbles and stones. Bedrock occurs in some areas of swiftly flowing current. The depth of the river varies from very shallow to over 18 metres during the wet season. These channels are important for the migration of over 100 species of fish.
Deep pools have been scoured by the swift currents in this section of the Mekong River. In the dry season these areas provide refuge for seasonally quiescent fish species and Irrawaddy dolphins. The invertebrate fauna of the walls of these pools is not known.
Sandbars are common on stretches of the Mekong in Stung Treng. Submerged in the wet season, these areas provide dry season roosting and breeding habitats for sandbar nesting waterbirds.