Big Fish

Click on image for larger version and caption

By Sylvia Wright

Graduate student Zeb Hogan works to save the world’s largest freshwater fish—the Mekong giant catfish—and raise the alarm about impending devastation of Southeast Asia’s fisheries.

Not many graduate students end up trying to save a fish as big as a bear. But that’s Zeb Hogan’s goal.

In 2000, 2001 and 2003, the conservation biology doctoral student waited the entire month of May for Thai fishers to catch giant catfish in the Mekong River at Chiang Khong. At this traditional fishing spot, 30 fish had been caught in 1995, only seven in 1997, merely two in 1998.

Every day Hogan sat on the patio at his guest house overlooking the river. As the muddy waters rolled by, he typed on his laptop, working through past years’ catch data and fishery statistics. Thousands of those fish flowed from his field notes into the computer. No giant catfish swam into the fishers’ nets.

“I’d go down to where they had their nets out and ask, ‘Caught any fish?’ And they never had,” Hogan said in a recent interview on campus between stints in Asia. “Here is a fish that has been caught for hundreds of years. Now it looks like it’s on the way out.”

Hogan, who had been studying fish migration in the area since coming to Thailand in 1996 on a Fulbright scholarship, decided to work on the conservation of the giant catfish. “With a species disappearing before my eyes, the more technical aspects of my research seemed less urgent.”

The Mekong River has one of most diverse freshwater fish faunas of the world, says Hogan’s doctoral adviser, Peter Moyle. It includes several other giant fishes that regularly reach 6 feet in length, such as the giant carp and freshwater stingray.

Like some of the California native fish that Moyle studies, the Mekong fish migrate hundreds of miles each year between downstream feeding areas and upstream spawning areas.

“The diverse fish fauna supports large fisheries that are extremely important to the health and economic well-being of local peoples—fisheries now threatened by the construction of hydropower dams and other problems,” Moyle said. “We hope that Zeb’s work will help call attention to a potential impending ecological and social disaster.”

To help protect the endangered fish, Hogan decided to start paying the Chiang Khong fishers to release any catfish they caught. But he was barely scraping by on small grants, and the catfish were expensive—a typical 400-pound fish sold for $3,000. He wasn’t sure he could afford to ransom a fish even if he got the chance.

But at another fishing place 1,000 miles away in Cambodia on the Tonle Sap River, the same giant catfish (Pangasianodon gigas) had one-fiftieth the worth of those in Thailand—and a few were still being caught. So Hogan headed for the Tonle Sap.

Since 2000, he has bought, tagged and released 21 adult giant catfish into the Tonle Sap River.

In November 2003, in part because of Hogan’s field work, the International Union for Conservation of Nature (IUCN) put the Mekong giant catfish on its Red List of critically endangered species, giving it worldwide attention.

Students in conservation biology increasingly find their progress-to-degree delayed by the discovery that the subject of their studies is heading for extinction. “Like Zeb, many of our students find themselves involved in on-the-ground efforts to save species and habitats,” Moyle said.

After spending much of 2000–03 mapping the giant catfish’s distribution and migratory patterns, Hogan is now resuming his doctoral work. He will tag other species of migratory fish in the Mekong, Tonle Sap and Cambodia rivers and study their genetic makeup to gather information about migration and dispersal.

He’s not giving up on the Mekong giant catfish, though. With the help of the Mekong Wetlands Biodiversity Program, an IUCN program, he’ll lead a workshop to develop a conservation plan for the fish. It will be the first time that experts in Thailand, Cambodia, Laos and Vietnam meet to discuss conservation options for the Mekong giant catfish.

And he’s working to increase public awareness of the giant catfish’s endangered status. He is helping a documentary filmmaker produce a film about the fish and, to encourage its preservation locally, he has written a children’s book, Samnang and the Giant Catfish. Published by Save Cambodia’s Wildlife, the book is beautifully illustrated by Cambodian artists Srey Bondal and Tor Vutha and printed in Khmer and English.

The book intertwines a story of the seasons of a giant catfish’s life with those of a young ambodian boy named Samnang. When the huge fish, which has become an old friend of Samnang’s, is caught by fishermen, Samnang persuades the men to let her go, because he believes that the fish “is special and very rare.”

For more information, see Web site news.nationalgeographic.com and search for
“Mekong catfish.”

Sylvia Wright writes about the environmental sciences for UC Davis. Photos by Zeb Hogan and Em Samy.