Abstract
Abstract
Lake Toba Caldera is one of the most extraordinary volcanic features formed during the Quaternary geological time. Currently, Lake Toba is a multi-functional lake, which is not only used as a source of water for the Sigura-gura power plant but also a tourist destination with a high level of visits. Lake Toba catchment area is part of the landscape of the Bukit Barisan Mountain Range extending northwest–southeast with irregular ridges and valleys, which have peaks with altitudes between 2000–3000 m above sea level, dominated by slope class (3–8%). Lake Toba is also a place for Indonesian native fishes having high values such as ikan batak (Tor spp. and Neolissochilus spp.). At present, however, the fishes are difficult to find. Generally, ikan batak prefers to live in a habitat with rocky bottoms, sand substrates, clear water, slow to heavy water flow, and the river environment is mostly in the form of primary forest. Description of physical characteristics of water bodies is needed to maintain an ecological system and to be used as a basis for determining fisheries protection zones. Bonan Dolok River is one of the rivers in Samosir Regency-North Sumatra where ikan batak can be relatively found. The river flows throughout the year and its morphology, which consists of a pool, riffle, and run and flow patterns such as laminar and turbulent are favored by ikan batak. Furthermore, the upstream area which is still covered by natural forest makes this area suitable as a conservation area for ikan batak itself.