Overview

Comprehensive Description

Biology

Adults live in rapid current of mountain streams.
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Distribution

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.
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Ba Bê, Bac Kan Province, Vietnam.
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Upstream Chay River, above Thác Bà Yên Bái, Yên Báo Province, Vietnam.
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Upstream Chay River, Ngòi Thuông, town Phuc Loi, Luc Yên County, Yên Bái Province, Vietnam.
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Asia: Reported from the Chao Phraya and Mekong basins (Ref. 26336) and Annam (Ref. 26580), Nam Ma basin, Red River and Nanpangjiang basins (Ref. 43281).
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China and northern Thailand.
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Physical Description

Size

Max. size

31.6 cm SL (male/unsexed; (Ref. 82789)); max. published weight: 1,000 g (Ref. 9671)
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Diagnostic Description

With wide mouth, width about 1.5 times in maximum head width; adults without barbels; last simple dorsal ray strong and serrated posteriorly (in specimens over about 10 cm SL); caudal peduncle 1.7-2.7 times longer than deep (Ref. 43281).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
O. gerlachi is a benthopelagic species which lives in rapid currents of mountain streams.

Systems
  • Freshwater
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Environment

benthopelagic; freshwater
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Onychostoma gerlachi

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2009

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)

Contributor/s

Justification
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.
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Population

Population
The population is thought to be decreasing although detailed numbers are unknown.

Population Trend
Decreasing
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Threats

Major Threats
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.
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Near Threatened (NT)
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Management

Conservation Actions

Conservation Actions
There are no conservation measures currently known to be in action at habitat or species level.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: commercial
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