The social and environmental impacts of dams have
attracted considerable concern (McCully 2001; Scudder
2005). In response, the World Commission on Dams produced
policy principles and guidelines (Scudder 2005;
WCD (World Commission on Dams) 2000), the hydropower
industry developed sustainability guidelines (IHA
(International Hydropower Association 2003), and damshave been decommissioned and removed in some countries
(Doyle et al. 2003). Although these changes have been
accompanied by a global decline in new dam construction,
many dams still continue to be built in Africa, Asia and
Latin America in response to demographic and economic
growth, and rising demand for energy.
This continued focus on hydropower investment is clearly
evident in Southeast Asia and especially in the Mekong river
basin. China completed the first dam across the mainstem of
the Mekong in 1995 (Li and He 2008), followed by two
others completed in 2003 and 2008, and a further five are
planned (Barlow et al. 2008). Further downstream, there are
over 100 proposals for new dams in the lower basin that lies
within Cambodia, Laos, Thailand and Vietnam. Of these, 11
are scheduled to be installed on the mainstem of the river
within the next decade. Seven of these are located in Laos,
two in Cambodia and two will be shared between Laos and
Thailand (MRC (Mekong River Commission) 2008).
This massive acceleration in plans for hydropower
development in the Mekong has led to growing concern over
the potential environmental, economic and social costs; in
particular, there is acute concern over the impact on the
basin’s fisheries. With an estimated annual harvest of
2.2 million tonnes of wild fish, the Mekong supports the
world’s largest inland fishery, annually worth US$2.2–3.9
thousandmillion at first sale and between US$4.3 and US$7.8
thousand million on retail markets (Hortle 2009). This catch
is essential for livelihoods, nutrition and food security, with
annual consumption in the lower basin between 29 and 39 kg
per capita and accounting for 47–80% of total animal protein
consumed (Hortle 2007). It also sustains livelihoods for
millions of people. In Lao PDR more than 3 million people
fish, mainly from the Mekong and its tributaries. In Cambodia,
80% of the 1.2 million people living around Tonle Sap
use the lake and its rivers for fishing (Ahmed et al. 1998).
Dams will bring a range of changes to the river and its fish
habitats (Postel 1997). In particular, altered flow regimes
will degrade the feeding and breeding habitats along the river
(Kummu and Sarkkula 2008), and the physical barrier of the
dam wall will stop migration (Barlow et al. 2008; Baran and
Myschowoda 2008). Because 40–70% of fish catch in the
Mekong depends on species that migrate long distances
along the Mekong mainstream and into its tributaries
(Barlow et al. 2008; Baran and Myschowoda 2008), these
fish stocks will be especially vulnerable to dams built on the
mainstem or lower reaches of tributaries.