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Rhodeus laoensis 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Cypriniformes Cyprinidae

Scientific Name: Rhodeus laoensis Kottelat, Doi & Musikasinthorn, 1998

Assessment Information [top]

Red List Category & Criteria: Vulnerable B1ab(ii,iii,v) ver 3.1
Year Published: 2012
Date Assessed: 2011-01-21
Assessor(s): Kottelat, M.
Reviewer(s): Gibson, C. & Allen, D.
Justification:
The species is only known from the Nam Theun and Nam Gnouang catchments in Lao PDR. It was was previously common throughout its geographic range but populations are decreasing as a consequence of the construction of numerous dams between 1999 and 2009, which now impact much of its range. This species has been observed in most water bodies with slow flowing water, from forest creeks to the main river. Juveniles are common along shores and adults prefer deeper waters. It spawns in mussels which are an obligate part of the life-cycle of this fish and the presence of a healthy mussel population is necessary for the survival of the species. The mussels on which they depend for spawning (and therefore their survival) are not expected to survive sand and sediment deposition that occurs in reservoirs.

Downstream of some of the dams, sand and sediments accumulate (due to reduced flow) and cover the habitat of the mussels. One stream in the species range (Nam Phao), is further affected by large accumulations of sand resulting from the construction of the road and the dam upstream of Laksao, sewage and pollution from Laksao, and gold mining. The population of the species is expected to be decreasing, and the species is assessed as Vulnerable based on its restricted EOO of 8,511 km2 and number of locations (estimated at between 5-10), and ongoing decline in habitat quality (of the species and its mussel host) as a result of pollution and impacts from dams.

Geographic Range [top]

Range Description:The species is known from the Nam Theun and Nam Gnouang catchments in the Mekong drainage, Lao PDR (Kottelat 1998, 2000; M. Kottelat pers. comm. 2011). The species' Extent of Occurrence is a maximum of 8,511 km2 (based on the area of sub-catchments of the two rivers where it is known from; this figure includes large areas of unsuitable habitat (e.g., reservoirs)).
Countries occurrence:
Native:
Lao People's Democratic Republic
Additional data:
Number of Locations:5-10
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species was previously common throughout its geographic range but it is decreasing as a consequence of the construction of numerous dams between 1999 and 2009, which now impact most of its range (M. Kottelat pers. comm. 2011).
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:The species has been observed in most water bodies with slow flowing water, from forest creeks to the main river. Juveniles are common along shores and adults prefer deeper waters. It spawns in mussels which are an obligate part of the life-cycle of this fish. The eggs hatch in the mussel and larvae remain in the mussel for a still unknown length of time, which might be up to several weeks. Therefore the presence of a healthy mussel population is necessary for the survival of the species. The identity of the mussel species in which the eggs are deposited is not yet known; a species tentatively identified as Pseudodon vondembushianus has been collected in the same area (Kottelat 1998, M. Kottelat pers. comm. 2011).
Systems:Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Unknown

Use and Trade [top]

Use and Trade:

This species is utilised as part of local subsistence fisheries (M. Kottelat pers. comm. 2011).

Threats [top]

Major Threat(s): The construction of numerous dams occurred from 1999-2009 and a great part of this species' known distribution is now flooded. Although the dams possibly do not directly impact the species, the mussels on which they depend for spawning (and therefore their survival) are not expected to survive sand and sediment deposition that occurs in reservoirs. Downstream of some of the dams, sand and sediment accumulate (due to reduced flow) and cover the habitat of the mussels. One stream in the species' range (Nam Phao), is further affected by large accumulations of sand resulting from the construction of the road and the dam upstream of Laksao, sewage and pollution from Laksao, and gold mining (M. Kottelat pers. comm. 2011).

Conservation Actions [top]

Conservation Actions: The part of this species' range upstream of the Nam Theun 2 reservoir is in a protected area where laws are expected to be enforced (M. Kottelat pers. comm. 2011).

Citation: Kottelat, M. 2012. Rhodeus laoensis. The IUCN Red List of Threatened Species 2012: e.T180780A1662013. . Downloaded on 15 October 2018.
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