Aaptosyax grypus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Cypriniformes Cyprinidae

Scientific Name: Aaptosyax grypus Rainboth, 1991
Common Name(s):
English Mekong Giant Salmon Carp
Taxonomic Source(s): Eschmeyer, W.N. (ed.). 2015. Catalog of Fishes. Updated 7 January 2015. Available at: (Accessed: 7 January 2015).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2acd ver 3.1
Year Published: 2011
Date Assessed: 2011-01-17
Assessor(s): Vidthayanon, C.
Reviewer(s): Ng, H.H., Rainboth, W., Kottelat, M., Kullander, S.O., Parenti, L. & Allen, D.J.
The Mekong Giant Salmon Carp has a wide range within the Mekong River, but is now present at very low densities in both adult and juvenile forms. Its population has been much reduced (by more than 90%) over the last decade (C. Vidthayanon, pers. comm.), as a result of overfishing and habitat degradation. The species is therefore assessed as Critically Endangered. This fish is also likely to be impacted in the future by development of mainstream dams, which will further limit its breeding success.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to the Mekong River basin, occurring from Lao PDR to northern Cambodia. It was described from a specimen taken from the Mekong at the entrance to the Mun River, Thailand.

The Mekong Giant Salmon Carp once occurred from the Lower Mekong, through the Khorat Plateau to Phnom Penh, but has recently been seen from Chiang Rai in northern Thailand (unconfirmed record). Its current distribution is northeastern Thailand and central Lao PDR, restricted to larger parts of rivers.
Countries occurrence:
Lao People's Democratic Republic
Possibly extinct:
Cambodia; Thailand
Additional data:
Lower elevation limit (metres):180
Upper elevation limit (metres):200
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species was once widespread in the mainstream Mekong River, but naturally rare and has been much reduced in recent years (Rainboth 1996). Its range has reduced and now larger individuals are very rarely found. It is rare in Lao PDR, and has likely disappeared from Thailand. Its population has reduced over the last decade by more than 90% (C. Vidthayanon, pers. comm.) as a result of overfishing and habitat degradation.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:The species mainly inhabits mainstreams, and frequently enter large tributaries. Breeds in summer, in clear water around rocky rapids in the Thai-Lao border. Breeds in faster flowing water/rapids.
Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Full Migrant

Use and Trade [top]

Use and Trade: Subsistence fishing by locals for food and sale in markets. In the past, there were some commercial-scale fisheries.

Threats [top]

Major Threat(s): Local overfishing (especially through drift gill nets), illegal fishing (explosives) impact its populations, and hydrographic change due to mainstream dams and climate change threaten its survival and recruitment. There are three further dams planned in the Thai part of the Mekong, within the species current distribution.

Conservation Actions [top]

Conservation Actions: Life history and population research are needed. Research is needed into population and habitat trends.

Citation: Vidthayanon, C. 2011. Aaptosyax grypus. The IUCN Red List of Threatened Species 2011: e.T9A13090494. . Downloaded on 20 September 2018.
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