An underwater expedition has confirmed the presence of some of the world’s largest and most threatened freshwater fish in a remote and barely studied stretch of the Mekong River in northeastern Cambodia. The findings included a 180-kilogram (400-pound) giant freshwater stingray that was captured and released in collaboration with local fishermen, but also revealed several “worrisome” threats facing the unique aquatic habitats.
During the weeklong investigation in Cambodia’s Stung Treng province earlier this month, the international team of underwater explorers and local fish biologists used remotely operated submersibles, baited video cameras, and dropcams suspended on long cables to capture the first ever videos of life in the Mekong’s deepest pools, which plunge down to 80 meters (260 feet).
“No one’s observed what’s going on underwater in this area before — it’s very deep water, very hard to study, and very inaccessible,” Zeb Hogan, a fish biologist and leader of the Wonders of the Mekong project, told Mongabay. The expedition was partly an effort to corroborate local fishers’ tales of catching giant fish in the pools, he added.