Chasing a Fish of Epic Proportions on the Mekong

Floating down the Mekong in his dinghy, Zeb Hogan is on the ultimate fisherman’s quest: to find the world’s largest freshwater fishes.

The American biologist plans to trawl 10 rivers around the globe, including the Nile, Amazon and Mississippi, looking for about 20 species of hulking fish such as the goliath catfish, Chinese paddlefish and North American lake sturgeon -- not to catch them, he says, but to save them.

“These big, amazing creatures all over the world, they might be goners, on their way out,” he says.

Right now Hogan is on the Mekong that flows through the Indochinese peninsula, looking for a stingray said to weigh more than 1,300 pounds -- as much as a full-grown longhorn steer.

He knows it’s out there; he photographed one in 2002. And smaller stingrays abound. As he passes villages on riverbanks or floating on the water, he sees children playing with severed stingray tails.

The 2,600-mile Mekong is known for the diversity and size of its river creatures, judging from the names of places along its banks, such as the Pool of the Giant Catfish and the Pool of the Giant Carp. In May, fishermen in Thailand landed a Mekong catfish that was 8 feet, 10 inches long and weighed 646 pounds. It’s believed to be the largest freshwater fish caught and measured. It ended up on dinner tables.

On his voyages, Hogan says, “the main question I’ll be asking everywhere is, what were populations like in the past, what are they now?” Here’s what he expects to find: “You’ll see a pattern that these populations of these large fish species are declining -- a lot.”

These are not aquatic sasquatches he’s looking for, but fish whose existence is a fact. The goliath catfish is still fairly common, Hogan says, and Wisconsin has a fishing season for lake sturgeon. The Chinese paddlefish is very rare, but a 275-pounder was caught on the Yangtze River in China on Dec. 11, 2003. There are said to be 650-pound carp, but none weighing more than 300 pounds has been seen in recent times, Hogan says.

Almost all maximum lengths and weights come from accounts over the ages by scientists, explorers and taxonomists and, Hogan says, “in many cases, have been verified by present-day scientists like myself. That is, after all, one of the main objectives of the project.”

Hogan, 31, of the University of Wisconsin in Madison, has worked on the Mekong since 1996. His research is supported by the World Wildlife Fund US, the National Geographic Society’s Emerging Explorers Program and outdoor-gear companies Marmot and Patagonia.

He’ll be working with other scientists studying the creatures, such as a biologist researching the Amazon’s arapaima, which can weigh 450 pounds, and a Texas freshwater guide who will help him study the alligator gar, which can reach 300 pounds.

As they move down the Mekong, Hogan and his two Cambodian assistants pass constant reminders of the importance of the river’s fish population to the 73 million people living along its banks. People busily mend nets, and at night, dozens of tiny candles in floating containers mark where nets have been laid in the water off Phnom Penh’s riverfront.

Along the way, Hogan and his assistants pepper fishermen with questions and pictures of their quarry.

The fishermen may not have caught or even seen the fish, Hogan says, but often will say they have heard about it being somewhere else. “Theoretically, that’s supposed to lead us to where the fish are.”

Not always, though. He says fishermen are hesitant to acknowledge that they have hooked a big one for fear of running afoul of Cambodian and international restrictions on hunting rare species. The penalties are small, but the fishermen don’t want the bother.

Hogan expects to finish in December 2006 and give his fish counts to the International Union for the Conservation of Nature and Natural Resources, or IUCN, which compiles the Red List of Threatened Species -- creatures threatened by overfishing, pollution, dams and alien aquatic life introduced by humans.

IUCN lists some of the giants as endangered or critically endangered, but for others, there simply isn’t enough data to judge.

“We have a sense that the world’s largest freshwater fish are disappearing really fast,” says Robin Abell, a WWF freshwater conservation biologist. “We do need to work to understand both the species and the threats to them.”

“The most exciting part for me,” Hogan says, “is that no one’s done this before.”

He believes the stingray ultimately will take the title as largest freshwater fish but says he will adhere to tough standards.

“If I don’t have a photo or a weight, to me, it’s not legitimate,” he said. “I can’t go just by word of mouth ... fishermen are famous for exaggerating the size of fish that they catch.”