WWF and National Geographic search for giant freshwater fish

Posted on 18 November 2004    
Children along the Mekong River Basin with several landed giant catfish (Pangasius gigas).
© WWF / Zeb Hogan
A search to find the world’s largest freshwater fish is underway on the Mekong River in Southeast Asia.
The WWF-National Geographic funded study, led by WWF science fellow Dr Zeb Hogan, will explore rivers and lakes around the world for such fish species as the Mekong giant catfish (Pangasius gigas), which is listed by The Guinness Book of World Records as the world's largest freshwater fish. 

Some catfish grow over 3m in length and more than 270kg. Scientists believe that larger species exist. 
“These are absolutely amazing animals. They are unique and beautiful but disappearing fast,” Hogan said.

“This study has the potential to set new records — we’re looking to find the largest freshwater fish in the world, identify where they live, and figure out why they are disappearing."

The disappearance of such freshwater fish is often the first warning sign of overfishing or other trouble in the rivers and lakes where they live. 

In addition to catfish, scientists will also be searching for giant stingrays, razor-toothed gars, massive carps, caviar-producing sturgeon, and predatory salmon. Many of these species are also threatened by overfishing and habitat destruction.  

“These giants are the freshwater equivalents of elephants and rhinos, and if they were visible to us on land the world wouldn’t stand by while they disappeared,” said Robin Abell, a freshwater conservation biologist with WWF-US.

“This study will give us new insight into how these species live and what threatens their survival. In the end, we’ll know better how to manage fishing and protect habitats to save the species for the future.”  
Despite their size, finding and studying these freshwater giants will not be easy. They are extremely rare and getting rarer, with some already listed on the World Conservation Union’s Red List of Threatened Species.

A century ago, the Mekong giant catfish was found the entire length of the river from Vietnam to southern China. Today, the populations are in decline, with scientists estimating that the total number of Mekong giant catfish has decreased by about 90 per cent in the past two decades alone. 
Dams are often cited as one of the major threats facing the catfish as they block the fish species migration. Without the ability to move up and down rivers, the fish have fewer opportunities to breed, cutting down overall numbers and genetic diversity. 

Navigation projects have also destroyed critical spawning grounds and overfishing has lead to depleted fish stocks and conflict between resource users, highlighting the need for more effective management strategies.  

"This is the first study to examine all of the world's giant freshwater fish," said Hogan.

"By examining this diverse group, we hope to understand why many species are declining nearly everywhere. Our goal is to draw those connections in the hopes that we can better protect them.” 

• The Mekong River Basin is home to more species of giant fish than any river on Earth. It is also the most productive fishery in the world, generating US$1.7 billion each year. Fish from the Mekong are also the primary source of protein for the 73 million people that live along the river. 

• The study is being funded by WWF's Conservation Science Programme and the National Geographic Society's Emerging Explorers Programme.

For further information:
Tom Lalley, Endangered Species Communications Officer
Tel: +1 202 778 9544
E-mail: tom.lalley@wwfus.org
Children along the Mekong River Basin with several landed giant catfish (Pangasius gigas).
© WWF / Zeb Hogan Enlarge

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