SBR- Content.pmd - INBO

7 - Fisheries2. Capture fisheries2.1 BiodiversityThe Mekong River Basin is characterised by a high degree of biodiversity and endemicity. That is,many of its fish species are only found in the Mekong Basin, 21 and often only in the basin of one ofthe Mekong’s tributaries (see for example Kottelat 2000).The number of fish species found in any river is difficult to determine because, besides fish specieswhich complete their life cycle in freshwater, there are other species that may or must spend part oftheir lives in the sea. Some of these typically live in the estuaries, while others have life cycles thatrequire them to move between river and ocean at well-defined and regular stages. 22It is thus not surprising that the number of fish species in the Mekong River is contentious. As thefollowing indicate, leading fish taxonomists give quite different estimates:• Rainboth (1996) – ‘The total number of species recorded or expected from the Mekong, asinferred from the known zoogeography of southeast Asia, includes about 1,200 species. Thisnumber will undoubtedly increase as additional taxonomic studies and fish surveys arecompleted.’• Kottelat (2001) – ‘There are documented records of about 700 species from the MekongBasin.’• Dr. Walter Rainboth (personal communication 2001) – ‘The new Atlas on the Fish of theMekong will include 1,700 species. Many of the species are marine vagrants.’• Dr. Tyson Roberts (personal communication 2002) – ‘1,100 freshwater species.’ICLARM’s Fish Base lists 748 species from the Mekong at the moment, 23 and MRC’s Mekong FishDatabase 2003 currently counts 924 species. 24There is, however, no doubt that the Mekong is among the most species-rich rivers in the world.The number of fish species per unit area of catchment in the Mekong is several times that found inthe Amazon River Basin. 25 Species cataloguing is incomplete, and further taxonomic studies arerequired in the upper reaches of tributaries, particularly in Lao PDR and Cambodia where new fishspecies still remain to be discovered. 26One notable aspect of the fish fauna is the large number of fish families present. In Laotian watersalone, the native fish fauna comprises 47 families. 27 The Mekong Fish Database 2003 lists 91families in the basin, which indicates that the Mekong has the highest number of fish families ofany river in the world. 28 In addition, the Mekong fishes, in common with fishes in other large riversis characterised by a high degree of within-species diversity (i.e. genetic diversity). 29The fish occurring in the lowlands and floodplains of the Mekong Basin have been broadly categorisedinto two groups – black fish and white fish. 30 Black fish, which are mostly fish-eating carnivoresand eaters of aquatic debris, live year round in perennial waters, including swamps, and makelimited local, lateral migrations. This group includes the families of snakeheads (Channidae), airbreathing catfishes (Clariidae), bagrid catfishes (Bagridae) and climbing perch (Anabantidae). 31105