SBR- Content.pmd - INBO

State of the Basin Report - 2003monitor (Varanus salvator), Bengal monitor (V. bengalensis), water dragon (Physignathis spp),Bocourt’s water snake (Enhydris bocouti), puff-faced water snake (Homolopsis buccata), reticulatedpython (Python reticulatus) and the Tonle Sap water snake (Enhydris longicauda), are all consumed.Both snakes and many turtle species are also exported and a substantial illegal export trade exists.Among the turtles, the Asian box turtle (Cuora ambioensis) from the upland areas of Lao PDR,Viet Nam and Cambodia is now considered vulnerable due to hunting. Another box turtle, Cuoragalbinifrons, is considered endangered and the formerly common Cuora trifasciata, appears to berare. The big-headed turtle (Platysternon megacephalum) is considered endangered and themangrove terrapin (Batagur baska) is now restricted to coastal mangroves, although it was oncefar more widespread.Data on amphibians within the basin are even more limitedthan data on reptiles. MRC (1997) lists 37 species ofamphibians in Lao PDR, and it could be expected that all ofthose would probably have occurred in the Mekong Basin.The status of populations of amphibians cannot be adequatelyassessed in view of the lack of data. The larger frogs areeaten by humans, so their populations will have declined inareas where human populations have increased.Fish tracking equipment is used tomonitor the migration patterns ofsome large endangered fish speciesThe fish fauna of the Mekong Basin is thought to beparticularly diverse. Documenting the actual diversity isdifficult for several reasons. There are many species whichare essentially marine, but which may briefly enter thechannels of the delta. Secondly, the fish fauna of the river areas yet incompletely known. A number of species have yet tobe described and named, and some parts of the basin have yetto be surveyed. For the purposes of this section, we will countonly species considered “true” freshwater species, and onlythose that have been described.Kottelat 10 notes that there are about 700 described species documented from the Mekong Basin,and he records 481 species from Lao PDR. Rainboth 11 documents nearly 500 species from theCambodian Mekong. The number of described fish species known from the Mekong Basin islarge, but not remarkably so. The Zaire/Congo Basin in West Africa has 669 species 12 and theAmazon about 1200. 13 However, there are other large rivers that are far less rich, including theNile in Africa with 320 species, 14 the Mississippi in North America with 241 15 and the Murray-Darling in Australia with only 28. 16The striking feature of the ichthyofauna of the Mekong is the great diversity of fish families.Rainboth 17 lists 65 families for the Cambodian section of the Mekong, and Kottelat 18 lists 50 forLao PDR. In contrast, Géry 19 lists only 47 for the Amazon, so that at the family level, the Mekongappears to be one of the most diverse rivers. The fish fauna of the Mekong is dominated by thefamily Cyprinidae, with Rainboth 20 listing 54 cyprinid genera from the Cambodian Mekong, andKottelat 21 listing 75 cyprinid genera and 193 species for Lao PDR, which is 40 percent of the total481 fish species he documents from Lao PDR.Two obvious changes have occurred in the fish fauna of the basin over recent times. One has beenthe introduction of a number of species either from other river basins in the region or from otherregions. Kottelat 22 lists seven species of fish that have been introduced from other basins in theregion, and 15 introduced from outside the region that are now established in the Mekong. Several32