Boundaries

This ecoregion comprises two sections in three countries that border the Strait of Malacca. The western section lies along the northern coast of Sumatra, from the Barumun drainage in the south to drainages just north of Medan, and inland to Lake Toba.  The eastern section includes the western coastal drainages of the Malay Peninsula, with the Muar River forming its southern border in Malaysia and the northern border falling just south of Krabi, Thailand. It extends inland as far as Lake Temenggor.

Terrestrial habitats

Sumatran montane rain forests [IM0159], Sumatran lowland rain forests [OM0158], Sumatran freshwater swamp forests [OM0157], Sumatran peat swamp forests [OM0160], Myanmar coast mangroves [IM1404], Tenasserim-South Thailand semi-evergreen rain forests [IM0163], Peninsular Malaysian rain forests [IM0146], and Peninsular Malaysian montane rain forests [IM0144] (WWF 2001).

Description of endemic fishes

There are 12 endemic species in the ecoregion, including five species of Betta such as the dusky betta (Betta fusca), crescent betta (B. imbellis), and toba betta (B. rubra). It also includes the Critically Endangered Encheloclarias curtisoma (IUCN 2012). It also includes an endemic genus, Bihunichthys (B. monopteroides).

The ecoregion’s peat swamp forests are unusual in that the waters are very acidic and host a relatively diverse community, including a number of extremely stenotopic endemics such as Betta livida, Parosphromenus harveyi, and Encheloclarias curtisoma.

Justification for delineation

Southeast Asian ecoregions were delineated using a bottom-up approach employing both published and unpublished field data and expert assessment (Abell et al. 2008; Kottelat et al. 1993, Kottelat & Whitten 1993, 1996). This ecoregion was separated from the Southern Central Sumatra [738] and Indian Ocean Slope of Sumatra & Java [737] ecoregions due to different faunal compositions between the bottom part of the ecoregion and those to the south and east. It also shares affinities with the Malay Peninsula Eastern Slope [ecoregion 734], including species such as Trigonostigma heteromorpha (M. Kottelat pers. comm. 2006).