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The Southwestern Sri Lanka Rivers and Streams ecoregion contains many endemic island species. More than one-fourth of the freshwater fish that have been discovered here are endemic -- they live only in the rivers and streams of southwestern Sri Lanka. Studies suggest that the number of undescribed species here is potentially quite large.
Most of Sri Lanka gets little rain and has only a few permanent rivers. But things are very different in the southwestern "Wet Zone." High mountains in the central part of the island are the source of many permanent rivers and streams that flow through this wet region. These support diverse types of plants, fish, and mussels. On their way toward the Indian Ocean, the waterways descend over many low ridges and wind through forests and valleys. Sri Lanka is home to 90 species of freshwater fish and 21 species of crabs. Yet these are just the ones that have been identified -- it's likely that far more exist. Twenty-six species of fish live only in the Southwestern Sri Lanka Rivers and Streams. Most of these fish are small and highly specialized to their habitat. The survival of several species is uncertain, including the two-spot barb, black ruby barb, cherry barb, and the black-lined barb. Other rare species that live in this ecoregion are the Jonklaas loach, spotted gourami, Wilpita rasbora, Martenstyn’s barb, and the pearly rasbora. Many of the fish of this ecoregion are important for commercial fisheries or for the aquarium trade.
Much of the forest in this ecoregion has been cut for timber and for clearing the land for agriculture, which causes soil erosion and water pollution. People have changed some of the slower waterways to create rice fields. They have also introduced fish and plants that compete with native species for food and habitat. And some native species are captured and sold to aquariums in other countries.
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