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World's Largest Catfish Species Threatened by Dam
Stefan Lovgren at Khone Falls, Cambodia
for National Geographic News. April 8, 2008
http://news.nationalgeographic.com/news/2008/04/080408-giant-catfish.html
 This is the sixth story in a continuing series on the Megafishes
Project. Join National Geographic News on the trail with project
leader Zeb Hogan as he tracks down the world's largest freshwater
fishes.
In the swift currents of the Mekong River in northern Cambodia,
fishers expertly navigate their longboats past rock outcroppings and
fallen logs.
But soon these wild waters may be tamed. Plans for the construction of
a large hydroelectric dam just across the border, at Khone Falls in
Laos, would permanently alter one of the most pristine areas in
Southeast Asia.
The dam is one of several being planned on the mostly untouched Mekong
River, which meanders through six countriesChina, Myanmar (Burma),
Thailand, Laos, Cambodia, and Vietnam.
The future of the Mekong was a key issue when the prime ministers of
those countries met for a regional summit earlier this week in the
Laotian capital of Vientiane.
The Don Sahong dam at Khone Falls, one of five dams that Laos is
planning along the Mekong, will block the deepest channel on the
section of the river that migratory fish pass through when the water
level is at its lowest, conservationists say.
One of those migratory fish is the critically endangered Mekong giant
catfish, which holds the record as the largest freshwater fish ever
caught. The record catch, made in northern Thailand in 2005, tipped
the scales at 646 pounds (293 kilograms).
"An impassable dam at the falls could cause the extinction of the
Mekong giant catfish species," said Zeb Hogan, a fisheries biologist
at the University of Nevada in Reno.
Hogan, who visited the Khone Falls area last week, heads the
Megafishes Project, a three-year effort to document the 20-plus
species of freshwater fish that measure at least 6.5 feet (2 meters)
in length or 220 pounds (100 kilograms) in weight.
Spawning Ground
Fishers at Khone Falls had long known that the giant catfish traveled
through their area.
But in 2007 Thai photographer Suthep Kritsanavarin for the first time
photographed a giant catfish caught at Khone Falls.
Giant catfish were once plentiful throughout the Mekong River basin,
but in the last century the population has declined 95 to 99 percent,
according to Hogan.
The massive fish is not targeted by fishers, but it is sometimes
caught as bycatch. In Cambodia, where the largest population of giant
catfish is found, eight of the giant fish were caught last year.
Although fishing is the biggest immediate threat to the giant catfish
in the Mekong, dams and habitat fragmentation could disrupt the
animal's ability to reproduce, Hogan said.
"There is only one known spawning ground for Mekong giant catfish, and
that spawning ground is in northern Thailand," he said.
"Until we know better, we have to assume that fish from Cambodia may
migrate to Thailand to spawn."
The construction of the Don Sahong dam, which is slated for completion
in 2010, would make that migration impossible, Hogan said.
Untouched
Advocates of the dams point to the enormous hydropower potential that
the Mekong offers to an energy-hungry region. With oil prices at
record levels, the projects have taken on added urgency, they say.
So far the Mekong runs almost uninterrupted; only China has dammed the
river at two locations in Yunnan Province.
One of the dams that China is now building will be second in size only
to the Yangtze River's Three Gorges Dam.
"China, as an upstream country, will never do anything that will harm
the interests of downstream countries," He Yafei, China's assistant
foreign minister, told reporters before last week's regional summit.
But officials in Vietnam, where the Mekong empties into the South
China Sea, say water extraction for farm irrigation upstream has
already caused ocean salt water to move inland, destroying rice
fields.
Conservationists likewise warn that the new dams could harm fish
stocks that millions of people throughout the Mekong depend on.
"Fisheries resources are essential to the population of the Mekong
Basin," said Eric Baran of the nonprofit World Fish Center in Phnom
Penh, Cambodia.
"In Cambodia, for instance, the fish catch contributes 65 to 75
percent of the animal protein of households."
More than a thousand fish species live in the Mekong River system, a
biodiversity second only to the Amazon in South America, Baran said.
In a report last year, the World Fish Center warned that the economic
benefits of the U.S. $300-million Don Sahong dam may be outweighed by
losses from local fisheries, whose production has been estimated at
over U.S. $2 billion a year.
Deep Channel
At Khone Falls the Mekong River drops up to 100 feet (30 meters) from
the Khorat plateau to the Mekong plain, forming a complex network of
narrow channels, called hoo in Lao.
Scientists have found that the area supports at least 201 fish
species, including several endemic or endangered species.
The area is also home to one of the few remaining concentrations of
freshwater dolphins in the Mekong.
The dam will block Hoo Sahong, the deepest channel and the only one
that migratory fish can pass through at the peak of the dry season, in
April and May, when the Mekong is at its lowest.
Nongovernmental organizations in Cambodia called on their government
this month to ask Laos for a construction moratorium on the Don Sahong
dam to allow for more environmental assessments.
Hogan admits that dams provide a number of benefits, including flood
control, water for irrigation, and electricity.
"But it is also important to consider the costs," he said, "especially
in an area where a large part of the population is dependent on fish
for food."
"From a migratory fish's perspective, there is nothing worse than a
dam."
Related Photo Story:
Giant Catfish Faces Dam Risk in Asia
http://news.nationalgeographic.com/news/2008/04/photogalleries/catfish-pictures/
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