Posted
on 28 July 2010
Wild populations of the iconic Mekong giant
catfish will be driven to extinction if
hydropower dams planned for the Mekong River
go ahead, says a new report by WWF.
The report, River of
Giants: Giant Fish of the Mekong, profiles
four giant fish living in the Mekong that
rank within the top 10 largest freshwater
fish on the planet (see list of top 10 at
bottom of page).
At half the length of
a bus and weighing up to 600kgs, the Mekong
River’s giant freshwater stingray (Dasyatis
laosensis) is the world’s largest freshwater
fish. The critically endangered and culturally
fabled Mekong giant catfish (Pangasianodon
gigas) ranks third at up to 3 metres in
length and 350kgs.
Dam will present unsurmountable
barrier for giant fish
“A fish the size of
a Mekong giant catfish, simply will not
be able to swim across a large barrier like
a dam to reach its spawning grounds upstream,”
said Roger Mollot, Freshwater Biologist
for WWF-Laos. “This would lead to the collapse
of the wild population of this iconic species.”
Current scientific information
suggests the Mekong giant catfish migrate
from the Tonle Sap Lake in Cambodia up the
Mekong River to spawn in northern Thailand
and Laos. Any dam built on the lower Mekong
River mainstream will block this migration
route.
The hydropower dam planned
on the Mekong River at Sayabouly Province,
northern Laos, is a threat to the survival
of the wild population of Mekong giant catfish.
The Sayabouly Dam is the first lower Mekong
River mainstream dam to enter a critical
stage of assessment before member countries
of the Mekong River Commission advise on
whether to approve its construction.
Mekong River home to
more giant freshwater fish than any other
“More giant fish live
in the Mekong than any other river on Earth,”
said Ms Dang Thuy Trang, Mekong River Ecoregion
Coordinator for the WWF Greater Mekong Programme.
“Currently, the Lower Mekong remains free-flowing,
which presents a rare opportunity for the
conservation of these species. But the clock
is ticking.”
The other Mekong giant
fish featured in the report are the "dog-eating"
catfish (Pangasius sanitwongsei), named
because it has been caught using dog meat
as bait, and the giant barb (Catlocarpio
siamensis), the national fish of Cambodia
and largest carp in the world. At 300kgs
each, these fish tie for fifth place on
the global top ten.
Dams will amplify the
impact of climate change on fisheries and
agriculture
However, the impacts
of lower Mekong River mainstream dams are
not restricted to these Mekong giants, they
would also exacerbate the impacts of climate
change on the Mekong River Delta, one of
the world’s most productive regions for
fisheries and agriculture.
Building the Sayabouly
Dam would reduce sediment flowing downstream
to the Mekong River Delta, increasing the
vulnerability of this area to the impacts
of climate change like sea level rise.
There are alternatives
WWF supports a delay
in the approval of the mainstream dams,
including the Sayabouly Dam, to ensure a
comprehensive understanding of all the positive
and negative impacts of their construction
and operation.
To meet immediate energy
demands, WWF promotes sustainable hydropower
projects on tributaries of the Mekong River,
prioritising those that already have hydropower
dams developed on them.
The Global Top 10 Giant
Freshwater Fish
1.Giant freshwater stingray (Himantura chaophraya)
600kg (500cm, 240cm disc width) Mekong River
Basin
2.Chinese paddlefish (Psephurus gladius)
500kg (700cm) Yangtze River Basin
3.Mekong giant catfish (Pangasianodon gigas)
350kg (300cm) Mekong River Basin
4.Wels catfish (Silurus glanis) 306kg (500cm)
Widespread in Europe and Asia
5.Giant pangasius (dog-eating catfish) (Pangasius
sanitwongsei) 300kg (300cm) Mekong River
Basin
6.Giant barb (Catlocarpio siamensis) 300kg
(300cm) Mekong River Basin
7.Arapaima (pirarucu; paiche) (Arapaima
gigas) 200kg (450cm) Amazon River Basin
8.Piraíba (laulau; lechero) (Brachyplatystoma
filamentosum) 200kg (360cm) Amazon River
Basin
9.Nile perch (Lates niloticus) 200kg (200cm)
Nile River Basin
10.Alligator gar (Atractosteus spatula)
137kg (305cm) Mississippi River Basin
