for National Geographic News
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 countries—China, Myanmar (Burma), Thailand, Laos, Cambodia, and Vietnam (see map).
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). (See photos of the grizzly bear-size catfish.)
"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.
(The Megafishes Project is partly funded by the National Geographic Society, which operates National Geographic News.)
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