Big Trouble for Asia's Giant Catfish

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Buy and Release

Hogan launched the conservation project in Chiang Khong, Thailand, in 2000 but moved it to Cambodia in 2001 due to the collapse of Thailand's giant catfish fishery. "Cambodia is now the last place in the world where the giant catfish is captured on a regular basis," he said.

But Cambodia's giant catfish numbers are also low. Fishers along the Tonle Sap River, a tributary to the Mekong, set bag nets from October to December. In 2000, fishers hauled out 11 giant catfish. In 2001 they caught seven. In 2002 they caught just five.

Hogan and Kong have hooked fishers on their conservation project. Whenever fishers catch an endangered fish they call the biologists, no matter what time of day.

The researchers rush to the river and pay the fisherman market price for the catch then measure, weigh, and release the fish downstream from the fishnets.

"We pay for the fish as an incentive for fishermen to report their catches and to keep rare species alive and in the river instead of dead on a dinner plate," said Hogan. Fishermen are also paid a little over U.S. $1 to return tags from recaptured fish.

Hogan says the money is not enough to give the fishers an added incentive to go after the endangered fish and thus does not influence their fishing behavior.

Mekong Migration

The researchers have tagged nearly 2,000 fish, most of them river catfish (Pangasianodon hypophthalmus). The fish are tagged in the Tonle Sap Lake and Tonle Sap River from October to December as they begin their winter migration.

Reports of the re-captured fish will allow the researchers to establish growth rates by comparing the weight and length of the fish from when they were first tagged to when they were captured. The re-captured fish also allow the scientists to track the fishes' spawning migration up the Mekong River.

"The migration study has conservation relevance because it demonstrates the importance of free-flowing rivers and the link between floodplain habitat like the Tonle Sap Lake and the spawning habitat of the Mekong River," said Hogan.

The researchers ultimately hope that several no fishing zones will be established in the region and that the Tonle Sap Lake, Tonle Sap River, and Mekong River will be recognized as critical habitat for migratory fish.

Conservation Status

Currently, the Mekong giant catfish P. gigas is listed as endangered by the World Conservation Union (IUCN) and is in the process of being re-designated as critically endangered.

While the Mekong river catfish (P. hypophthalmus) is not recognized as endangered, Hogan said observational data suggests that its populations are declining rapidly, with catches down 90 percent from 20 years ago.

The range of the giant carp (Catlocarpio siamensis) has also declined and is a focus of Hogan's conservation research.

Sretthachau said fishing is a way of life for the people of the Mekong River Basin and the loss of these species "means millions of people will lose their food security, livelihoods, and economic system."

Hogan and his colleagues seek to raise conservation awareness through their forthcoming book The Long Journey of the Giant Catfish. Once published, the book will be distributed to Cambodian school children.

"Since the Mekong giant catfish is migratory, the protection of the Mekong giant catfish may benefit many other species that use identical habitat," said Hogan.

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