The significance of the ecosystem value and its effect on the fish distribution in Sibau sub-watershed

Abstract

Betung Kerihun National Park (TNBK) is the largest conservation area in West Kalimantan which has an area of 816,693.40 ha with high species diversity, both flora and fauna. One of the constituent ecosystems in TNBK region is its watershed. TNBK region has four sub-watershed which acts as a receiving area and divert rain water from tributaries to the main river (Kapuas River), namely Embaloh, Sibau, Mendalam and Kapuas sub-watersheds. The objective of this study is to evaluate the sub-watershed ecosystem value which affect to distribution of the fish. The Sibau sub-watershed, one of the four sub-watersheds in TNBK plays as supporting ecosystems which have a high influence on the distribution of fish species. This zone also has a function as a site for the local people activity and become as a buffer area. Fish monitoring data in 2018 conducted on three rivers i.e. Peang River, Menyakan River and Sibau River which locateson the traditional zones show a high status indiversity. There are 25 species of fish which successfully recorded in the fish distribution monitoring with a total of 242 individuals. The common species were Batu fish (Labocheilos falcifer), Seluang fish (Rasbora voltzii), and Kenyuar fish (Luciosioma setigerum). The biophysical conditions of the river in the Sibau sub-watershed seem suitable for the habitat of many fish species. The determinant factors were water temperature, turbidity, river canopy and pH. The obtained fish can also be categorized as a bioindicators of a waters by considering of those aspects. Most of the fish species are directly or indirectly dependent on the forest or river in providing food such as plant materials (leaves, flowers, fruits) or invertebrates. Sibau sub-watershed has a rich of vegetation, as well the type of alluvial soils that make up the land. The alluvial soils have better fertility rates than other types of soils. In addition, high rainfall (2,863 - 5,517 mm/year) and dense river canopy also have an important influence on fish life in the Sibau sub-watershedwaters.