Cambodia: Big-name divers explore deepest Mekong pools in key survey

The Phnom Penh Post via Asia News network

16:15 JST, May 25, 2022

A group of well-known underwater explorers have dived to a depth of about 75 meters below the surface of the Mekong River in Cambodia, an important body of water that is the last habitat of the world’s largest freshwater fish.

The deepest exploration mission ever carried out in the Mekong is an international effort led by the U.S. Agency for International Development (USAID) under the Wonders of the Mekong project, which began on April 23 and finished on April 27.

“We are exploring deep into the Mekong, another world — a realm within a hidden realm, a pitch-black space inhabited by rare and unusual fish like the Mekong giant stingray and giant catfish,” said Zeb Hogan, a fish biologist and leader of the USAID-funded project.

The area that the scientists will focus on is located just downstream of a Ramsar wetland of international importance. The region is dominated by flooded forests, rocky outcrops, sand bars, braided channels, deep pools and rapids and riffles.

This area also is home to many of the Mekong’s more than 1,000 fish species, including the bizarre two-faced carp, giant goonch catfish, and the striped catfish, once a staple food in Cambodia.

Researchers believe that these areas are critically important as dry-season fish refuges and important spawning areas, and perhaps as the last habitat of several endangered giant fish. It is a region that is recognized as special and protected by local communities.

To study these important areas, Hogan — and project co-leader Sudeep Chandra — teamed up with biologists from the Fisheries Faculty of the Royal University of Agriculture; deep sea researcher Kakani Katija and her team from the Monterey Bay Aquarium Research Institute; and Kenny Broad, University of Miami professor, environmental scientist, cave diver, and the 2011 National Geographic Explorer of the Year. They are all specialists in the exploration and study of extreme underwater habitats.

In a press release seen by The Post on April 29, Hogan said: “The biggest challenge will be getting down to the bottom. Its deepest areas are below sea level. Besides being dark and silent, the waters could be obscured by particulates.”

For their exploration, the team used unmanned submersibles equipped with lights and cameras, drop cameras suspended on long cables, and use baited video cameras as their eyes and ears.

To assess the foreign environment, equipment that measures depth and flow and maps the river bottom and currents were deployed.

The team’s basecamp is adjacent to one of the Cambodian Mekong’s deepest pools and a fish reserve designed to protect spawning fish.

The area itself is dotted with islands occupied by small fishing camps, nomadic fishers that move from island to island, season to season. Upstream, across the border in Laos, is Khone Falls, the Mekong’s only main channel waterfall.

Hogan said that these deep pools may even have the potential of being used as introduction sites for endangered fish, similar to what the Wonders of the Mekong team did last month in the Tonle Sap Lake.

Chea Seila, program manager for Wonders of the Mekong, said in the press release: “This is one of many Wonders of the Mekong projects that seeks to protect a healthy, connected river, and the people, fisheries, wildlife, and water quality that the river supports.”

Chhut Chheana, communications coordinator for USAID Wonders of the Mekong, told The Post on May 1: “The exploration was conducted in the Mekong Ramsar area, which is from Stung Treng provincial town to the Lao border.”