|Scientific Name:||Tenualosa thibaudeaui (Durand, 1940)|
|Red List Category & Criteria:||Vulnerable A2bcd ver 3.1|
|Reviewer(s):||Kottelat, M. & Juffe Bignoli, D.|
This species is endemic to the Mekong basin. The population is inferred to have declined by at least 30% over the last 10-15 years, and had undergone additional decline during 1970-1990. Causes of this decline are overfishing and dam construction. Assessed as Vulnerable based on population reduction caused by known threats that have not ceased, and the species is likely to be greatly impacted my mainstream dams on the Mekong if they were to be constructed.
|Previously published Red List assessments:|
|Range Description:||The species is endemic to the Mekong basin from northern Thailand to the Mekong Delta including the Tonle Sap Lake in Cambodia. Poulsen et al. (2004) considered it possible that the species distribution might extend into Myanmar and southern China.|
Native:Cambodia; Lao People's Democratic Republic; Thailand; Viet Nam
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The species is seasonally and locally common at the beginning of the flooding season. Population decline is suspected to have reached 30% (C. Vidthayanon pers. comm. 2010) over the last 10-15 years, continuing a decline that had been observed in the 1990's by Baird and Roberts (1993). The species was previously abundant in the Khone Falls area but is now considerably rarer (Roberts 1993). Baird and Roberts (1995) reported that this species had declined the most of all the species that feature in the Khone Falls fishery since the 1970s; only four specimens were observed during the 15-day migratory period at the waterfalls in June-July 1993, and only a few individual fish were caught by fishermen in November-January 1993-94. Few were caught at the Khone Falls over the period 1993 to 1999 (Baran et al. 2005).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This species is found in rivers and large tributaries and it also moves to floodplain and lakes. It is strongly migratory, moving from the Tonle Sap Lake in Cambodia, and passes upstream through the Khone Falls in southern Lao PDR. The species grows to c.60 cm in length (Mattson et al. 2002). It is a filter-feeder.|
There are at least two populations in the Mekong (Poulsen et al. 2004); one around Xayaboury in northern Lao PDR and upstream, the other in the lower Mekong from the Mekong Delta to Paksan in Lao PDR, downstream of Vientiane. The latter may represent more than one population, e.g., one above and one below the Khone Falls (Poulsen et al. 2004). The species is thought to spawn mid-stream, with juveniles feeding in flooded floodplain habitats and major tributaries. Deep pools in the Mekong mainstream highly vulnerable to impacts from dam operation, are considered important for the population between Stung Treng and Kratie in Cambodia.
|Generation Length (years):||4|
|Movement patterns:||Full Migrant|
|Use and Trade:||This species is heavily fished throughout its range. Roberts and Baird (2005) ranked the species amongst the highest socioeconomic value species in the Khone Falls fishery in Lao PDR. It is especially vulnerable to gill nets (Poulsen et al. 2004), and is a valued food fish throughout its range.|
|Major Threat(s):||The causes of population decline are overfishing for human consumption, and habitat degradation due to infrastructure development, especially dams which block species movements. The species is considered to be vulnerable to impacts from mainstream dam development on the Mekong (ICEM 2010). Baird (2009) noted that the proposed Don Sahong dam at the Khone Falls would impact migration of the (lower Mekong) population.|
|Conservation Actions:||Management of the species fishery is needed throughout the species range, along with research into the impacts of current and proposed dams on the species migration routes.|
Baird, I.G. 2009. The Don Sahong Dam: Potential Impacts on Regional Fish Migrations, Livelihoods and Human Health. POLIS Project on Ecological Governance, University of Victoria.
Baran, E., Baird, I.G., and Cans, G. 2005. Fisheries bioecology at the Khone Falls (Mekong River, Southern Laos). WorldFish Center, Penang, Malaysia.
ICEM. 2010. MRC SEA for Hydropower on the Mekong Mainstream (Opportunities and Risks): National scoping consultation summaries: Annexes & supporting materials. International Centre for Environmental Management.
IUCN. 2011. IUCN Red List of Threatened Species (ver. 2011.1). Available at: http://www.iucnredlist.org. (Accessed: 30 June 2017).
Mattson, N.S., Buakhamvongsa, K., Sukumasavin, N., Tuan, N. and Vibol, O. 2002. Mekong giant fish species: on their management and biology. MRC Technical Paper. Mekong River Commission, Phnom Penh.
Poulsen, A.F., Hortle, K.G., Valbo-Jorgensen, J., Chan, S., Chhuon, C.K., Viravong, S., Bouakhamvongsa, K., Suntornratana, U., Yoorong, N., Nguyen, T.T., and Tran, B.Q. 2004. Distribution and ecology of some important riverine fish species of the Mekong River Basin. MRC Technical Paper. Mekong River Commission, Phnom Penh.
Roberts, T.R. 1993. Artisanal fisheries and fish ecology below the great waterfalls of the Mekong River in southern Laos. The Natural History Bulletin of the Siam Society 41: 31-62.
Roberts, T.R. and Baird, I.G. 1995. Traditional fisheries and fish ecology on the Mekong River at Khone waterfalls in southern Laos. The Natural History Bulletin of the Siam Society 43: 219-262.
Vidthayanon, C. 2008. Field Guide to Fishes of the Mekong Delta. Mekong River Commission, Vientiane.
|Citation:||Vidthayanon, C. 2011. Tenualosa thibaudeaui. The IUCN Red List of Threatened Species 2011: e.T21627A9303248.Downloaded on 18 March 2018.|
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