Washington, April 9 : The construction of a large hydroelectric dam in Laos might endanger the existence of the Mekong giant catfish, which is the world's largest catfish species.
According to a report in National Geographic News, the Don Sahong dam, being constructed 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.
The Don Sahong dam, which is 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, according to conservationists.
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.
According to Hogan, giant catfish were once plentiful throughout the Mekong River basin, but in the last century, the population has declined 95 to 99 percent.
Though fishermen do not target the massive fish, it is sometimes caught as a 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," said Hogan.
Hogan indicates that there is only one known spawning ground for Mekong giant catfish, which is in northern Thailand.
"Until we know better, we have to assume that fish from Cambodia may migrate to Thailand to spawn," he said.
"The construction of the Don Sahong dam, which is slated for completion in 2010, would make that migration impossible," Hogan added.
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.
"From a migratory fish's perspective, there is nothing worse than a dam," said Hogan.