Biologist trolls world’s rivers for the big ones

PHNOM PENH, Cambodia - Floating down the Mekong in his dinghy, Zeb Hogan is on the ultimate fisherman’s quest: to find the world’s largest fresh- water fishes.

The American biologist’s search will take him to 10 rivers around the globe, including the Nile, Amazon and Mississippi. He is looking for about 20 species of hulking fish such as the goliath catfish, Chinese paddlefish and North American lake sturgeon.

The goal is not to catch them, he said, but to save them. “These big, amazing creatures all over the world, they might be goners, on their way out,” he said.

On the Mekong River, which flows through the Indochina Peninsula, Mr. Hogan is looking for a stingray said to weigh more than 1,300 pounds — as much as a full-grown longhorn steer.

He knows it is 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 of its river creatures, as well as their size, to judge from places along its banks named the Pool of the Giant Catfish, or the Pool of the Giant Carp. In May, fishermen in Thailand landed a Mekong catfish that weighed 646 pounds and was 8 feet, 10 inches long. It is thought to be the largest freshwater fish ever caught and measured. It ended up on dinner tables.

On his voyages, Mr. Hogan said, “the main question I’ll be asking everywhere is what were populations like in the past, what are they now? You’ll see a pattern that these populations of large fish species are declining — a lot.”

These are not aquatic sasquatch he is seeking — the legendary giant primates also called Bigfoot — but fish whose existence has been proved.

The goliath catfish is still common, Mr. Hogan said, and Wisconsin has a fishing season for lake sturgeon. The Chinese paddlefish is 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 more than about 300 pounds has been seen in recent times, Mr. Hogan said.

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

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

He will be working with other scientists studying the creatures, such as a biologist researching the arapaima of the Amazon — said to be the world’s largest scaled freshwater fish, 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 putter down the Mekong, Mr. Hogan and his two Cambodian assistants pass constant reminders of the importance of the Mekong’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 placed in the water off Phnom Penh’s riverfront.

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

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

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