Stefan Lovgren for National Geographic News July 10, 2006
In honor of the King of Thailand's 60th year on the throne, fishers in northern Thailand have promised to stop catching the critically endangered Mekong giant catfish.
The largest freshwater fish in the world, the giant catfish can grow up to 10 feet (3 meters) long and weigh 650 pounds (300 kilograms).
It is found only in the Mekong River system, which runs through China, Laos, Thailand, Cambodia, and Vietnam.
More than 60 fishers made the pledge to stop catching the giant fish at a ceremony held last month in the northern city of Chiang Kong. It was one of several events to celebrate Thai King Bhumibol Adulyadej's reign.
Fishers in neighboring Laos have also vowed to stop hunting the giant fish.
"[This] is the most significant development in the conservation of the Mekong giant catfish in the last ten years," said Zeb Hogan, an associate research biologist at the Mekong Wetlands Biodiversity Conservation and Sustainable Use Program.
Conservationists say that while the ban is an important step toward saving the giant catfish, more has to be done before the unique species is off the hook.
As part of that effort, Hogan runs a tracking program in which he tags the fish to discover their spawning grounds and to study their migration patterns.
"This project is the first ever large-scale attempt to use underwater biotelemetry to study fish migrations in the Mekong River Basin," Hogan said.
Hogan's research is funded in part by the National Geographic Society. (National Geographic News is part of the National Geographic Society.)
he giant catfish were once plentiful throughout the Mekong River system, but in the last century the population has declined 95 to 99 percent, Hogan says.
He estimates there may only be a few hundred adult giant catfish left in the system today.
In 2003 the species was listed as critically endangered by the World Conservation Union after research showed its numbers had fallen by at least 80 percent since 1990.
The decision to stop the commercial harvest of giant catfish in Thailand, where it is known as pla beuk, may be particularly important, because conservationists believe the fish may spawn in Thai waters.
"In the past, fish have been harvested during their spawning migration but before they had a chance to reproduce," Hogan said.
"The fishing ban affords migrating fish the opportunity to spawn in their natural environment."
The talks to stop the hunt in Thailand were initiated in 2004 by the Mekong Wetlands Biodiversity Program, the fishers of Chiang Kong, and the then-senator of Chiang Rai Province, Tuenjai Deetes.
Sixty-eight fishing families called the Mekong Giant Catfish Club have agreed to stop the practice.
In return, the fishers are being paid U.S. $500 for each giant-catfish net they surrender.
"This is a great commitment from the fishers," Senator Deetes told the Associated Press.
"Every fisherman will stop fishing the giant catfish forever."
The fishers are entitled to conduct a "public demonstration catch" each year to preserve the traditional culture and methods of catching the fish. A maximum of two giant catfish may be caught and then released live back into the river.
The impact of the Thai fishing moratorium on the species' population remains to be seen.
Before last month's ban the catch in Thailand had already dipped dramatically from its peak in 1990, when 65 giant catfish were caught.
Only four giant catfish were caught in Thailand last year, including one 646-pound (293-kilogram) fish that is believed to be one of the largest freshwater fish ever caught.
Now neighboring Cambodia appears to be home to the largest remaining populations of wild giant catfish.
Over the past five years the giant-catfish catch there has been higher than in Thailand.
While it is illegal to catch the species in Cambodia, fishers there inadvertently harvest it as bycatch.
"The harvest [in Cambodia] is very difficult to control," Hogan said.
He says both the Cambodian and Thai areas of the Mekong have to be well managed to ensure the survival of the species.
"Cambodia and Thailand play different roles in the life cycle of giant catfish," he said.
"Northern Thailand is a spawning ground, whereas the Tonle Sap lake [in Cambodia] is a rearing area."
For its tracking program, Hogan's team has installed underwater receivers along the Mekong from Thailand to Laos.
"It's a beautiful stretch of river and thought to be prime spawning habitat for a variety of fish, including the Mekong giant catfish," Hogan said.
The team—which includes scientists from the Thai Department of Fisheries, the University of Idaho at Boise, and the Monterey Bay Aquarium in Monterey, California—has tagged and released 38 large fish, including 18 hatchery-reared giant catfish and 19 other endangered fish.
"The conservation value of this project is high, because it will enable greater understanding of the movement and ecological requirements of threatened migratory fish in the Mekong River Basin, of which almost nothing is currently known," Hogan added.
Early signs show that the hatchery-bred giant catfish move downstream toward the remote Xaignabouri area of Laos , while wild fish may move upstream to Myanmar (Burma) and China.
Hogan also tagged and released a wild giant catfish that was caught by fishers in Laos in early May.
Unfortunately it was recaptured and killed in Thailand a few hours after it had been released.
"Had the fish lived, it would have provided by far the best scientific information that's ever been available on Mekong giant catfish or any other Mekong River species," Hogan said.