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World's Largest Fish Caught in Thailand

GLAND, Switzerland, June 29, 2005 (ENS) - A Mekong giant catfish believed to be the world's largest freshwater fish has been caught in Chiang Khong, northern Thailand by local fishermen, says a WWF scientist studying giant freshwater fish in the Mekong River Basin. But with the fishing record comes a warning that Southeast Asia’s largest and rarest fish is critically endangered and disappearing fast.

The largest Mekong giant catfish, Pangasianodon gigas, in the record since 1981, the 292 kilogram (644 pound) fish was caught on May 1.

“I’m thrilled that we’ve set a record," said Dr. Zeb Hogan, WWF conservation science fellow, "but my excitement is tempered by the fact that these giant fish are poorly studied and critically endangered. Some, like the Mekong giant catfish, face extinction.”

A century ago the Mekong giant catfish was found along the entire length of the river from Vietnam to southern China. Today, the population is in decline, scientists estimate the number has decreased by about 90 percent in the past 20 years.

catfish

Thai fishermen netted what is thought to be the world’s biggest freshwater fish, a Mekong giant catfish,in the Mekong River, northern Thailand.May 1, 2005. (Photo © WWF/Suthep Kritsanavarin)
Until recently, large individuals of this species were caught often in Thailand, particularly at Chiang Khong near their reported spawning grounds.

At this traditional fishing spot, 30 of the enormous fish were caught in 1995, but only seven in 1997, and just two in 1998. Although a few of the giant fish have been caught in the last two seasons, none were captured there in the preceding three years.

The Mekong giant catfish is one of a number of giant fish species under investigation in a WWF and National Geographic Society joint conservation project exploring rivers and lakes around the world seeking evidence of the largest fish fish on Earth.

But as project leader Hogan says scientists must work quickly to study and conserve them before all these enormous fish are gone.

“My study of giant freshwater fish is showing a clear and global pattern - the largest fish species are disappearing," says Hogan. "In many places, large species are now so rare that the opportunity to study them may soon be lost.”

The Mekong River Basin is home to more species of giant fish than any other river on Earth. It is also the most productive river fishery in the world, generating $1.4 billion each year, and providing the primary source of protein for the 73 million people that live along the river.

Dams are often cited as one of the major threats facing the giant catfish as they block migration routes. Without the ability to move up and down rivers, the fish have fewer opportunities to breed, cutting down overall numbers and genetic diversity.

Hogan

As a doctoral student in conservation biology at the University of California-Davis, Zeb Hogan swam with the Mekong giant catfish he was studying before releasing them, to assess their strength and ability to swim on their own. (Photo courtesy UC Davis)
Despite mounting environmental concerns, the Asia Development Bank is promoting many large hydrodams along the Mekong River and its tributaries, beginning with sites in the upper watersheds of China's Yunnan province, Laos, Cambodia, and Vietnam.

Over the past 10 years, more than 100 large dams have been proposed for the Mekong basin by the Asian Development Bank (ADB) and the Mekong River Commission.

In August 2003, an ADB report recommended the construction of a regional power grid in mainland Southeast Asia fueled entirely by hydropower. Twelve dams in Burma, China and Laos were proposed to generate power for consumers in Thailand and Vietnam.

In addition, navigation projects have destroyed critical spawning grounds. Overfishing has led to depleted fish stocks and conflict between resource users, highlighting the need for more effective management strategies.

WWF is urging governments to regulate the development of dams and reduce overfishing in freshwater ecosystems to preserve large fish species, such as the Mekong giant catfish.

Jamie Pittock, head of the WWF’s Global Freshwater Program, said today, “This catfish is as heavy as a grizzly bear. It’s amazing to think that giants like this still swim in some of the world’s rivers. If they were visible to us on the land we wouldn’t stand by calmly and watch them disappear. This amazing species could be gone within the next few years if nothing is done to save it.”

WWF has been working in the Mekong River Basin for more than 10 years. The group says it has chosen the Mekong giant catfish as one of its flagship species because the conservation measures needed to protect it would also help protect a whole range of other species, particularly other migratory fish, and help maintain the tremendously productive fisheries of the Mekong.

On June 15 WWF and Cambodian officials released four adult Mekong giant catfish to the wild at the junction of the Tonle Sap and Mekong Rivers, to boost to catfish numbers in the Mekong Basin and to study the habits of the huge fish.

ceremony

WWF International Director General Claude Martin (right, seated) with Cambodian Fisheries Minister Chan Sarun at the Mekong giant catfish release. (Photo © WWF Cambodia)
WWF International Director General Dr. Claude Martin, Director General, and Cambodian Fisheries Minister Dr. Chan Sarun presided over the release ceremony near the Royal Palace in the Cambodian capital of Phnom Penh, close to where the fish were originally captured from the wild seven years ago.

The four catfish, each weighing some 50 kilograms (110 pounds) and measuring around 1.5 meters (59 inches) in length, were raised in a pond after being havested from the wild as tiny fry.

"The addition of four adult fish to the breeding population of a species, where only around five to 10 similar-sized individuals are caught each year in Cambodia, represents a significant contribution to the continued survival of this species in the wild,” said Martin.

The Cambodian Department of Fisheries has collaborated with several organizations to release and tag several of the catfish to better understand their migration routes.

"We want to keep the fish alive and return them to the wild," said Minister Chan Sarun.

Ing Vannath, the fish farmer who caught and reared the four giant catfish fish in his ponds, was at the release ceremony to see them off. “I wish to repay the favor to these gigantic fish by returning them to their natural habitat and to allow them the chance to swim freely and help maintain the dwindling wild population of this unique Mekong species,” he said.

The four catfish were fitted with tags prior to their release to alert fishermen who catch them accidentally of their protected status.

After spending so much of their lives in captivity, it is not known if these fish know how to migrate and spawn. There is a chance that they will fail to adapt to life in the river at all, but Martin is hopeful.

"Subsequent capture and release may demonstrate that the fish have not only been able to survive," he said, "but have also managed to retain their instinct to migrate and to reproduce."