|Scientific Name:||Onychostoma gerlachi|
|Species Authority:||(Peters, 1881)|
Barbus gerlachi Peters, 1881
Varicorhinus babeensis Nguyen & Nguyen, 2001
Varicorhinus gerachi (Peters, 1881)
Varicorhinus gerlachi (Peters, 1881)
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor/s:||Jenkins, A., Kullander, F.F. & Tan, H.H.|
|Reviewer/s:||Collen, B., Darwall, W., Ram, M. & Smith, K. (SRLI Freshwater Fish Evaluation Workshop)|
O. gerlachi has been assessed as Near Threatened because of an inferred population decline of 30% in the past three generations within the Mekong and Chao Phraya basins. This is as a result of high levels of pollution and a large number of hydrological changes, including dams, in this area.
It is thought that these threats exist throughout the range of O. gerlachi, however this may not be to the extent of the threats in the Mekong and Chao Phraya basins; this species has been assessed as Near Threatened, with an inferred total population decline of 20-29% over the past three generations.
|Range Description:||O. gerlachi is known from China, Thailand, Lao PDR, and Viet Nam; this species has been reported from the Chao Phraya, Mekong, Nam Ma, Hong (Red River) and Nanpangjiang basins.|
Native:China; Lao People's Democratic Republic; Thailand; Viet Nam
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population is thought to be decreasing although detailed numbers are unknown.|
|Habitat and Ecology:||O. gerlachi is a benthopelagic species which lives in rapid currents of mountain streams.|
Many of the river basins in which O. gerlachi is found, in particular the Mekong and Chao Phraya basins, have been greatly affected by water pollution,; a UNESCO report (2006) states that 'the Chao Phraya River exhibited serious organic and bacterial pollution that was a threat to many species of aquatic life.'
There are a number of large dams and other water diversion projects in both the Chao Phraya and Mekong basins, which are an additional threat to O. gerlachi; effects of developments such as these to the freshwater ecosystem include alterations to the hydrological cycle, and changes to the levels of sedimentation and dissolved O². More dams are currently under construction and planned for the future. Water from both the Chao Phraya and Mekong Rivers is used for agricultural irrigation and to supply urbanised areas, causing further disruption to the natural hydrological cycle.
Details of the threats within the Nam Ma, Hong and Nanpangjiang basins are not known, however it is likely that these are also affected to at least some extent by pollution and man made hydrological changes; the Hong (Red) river basin in particular is known to have a relatively high population density, and therefore pollution associated with urbanisation is likely.
|Conservation Actions:||There are no conservation measures currently known to be in action at habitat or species level.|
|Citation:||Jenkins, A., Kullander, F.F. & Tan, H.H. 2009. Onychostoma gerlachi. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 19 April 2014.|
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