Just after dawn on May 5, scientists working along a stretch of Cambodia’s Mekong River released a giant, endangered freshwater stingray that had been caught with a fishing line. At 13 feet and 400 pounds in length, the giant animal pancake was bigger than a hibachi table.
“It was shaking and I said to her, ‘Calm down, we’ll release you soon,'” said Chea Seila, a coordinator for the Wonders of the Mekong Project.
The giant freshwater stingray, Urogymnus polylepis† is the world’s largest species of rays, also known as whipray. With dark brown tops and creamy white bottoms, the animals glide across riverbeds in search of fish and invertebrates. Though they can grow to epic proportions, over-harvesting for stingray meat, deaths from fishing net accidents and habitat fragmentation and degradation from dams, pollution and other human activities have endangered the animals.
After receiving a call from the fisherman who caught the stingray, Ms. Chea and her team drove through the night for eight hours to assist in its release. They arrived at 3am and waited with the fish until the sun came up. More people were needed to carefully move the animal, which was armed with a venomous barb that could be more than a foot long and capable of piercing bones.
Before freeing the stingray, Ms. Chea and her colleagues took non-invasive samples that would aid future study of the species. Then they helped lead the colossus back to the depths of the Mekong.
“She calmly swam away but then reappeared, making us feel so, so happy,” Ms Chea said.
That a stingray of this size can still be found in these waters was extraordinary, the experts said.
“It shows that nature is so beautiful, but also resilient,” said Sudeep Chandra, a limnologist at the University of Nevada, Reno and co-scientist with the Wonders of the Mekong Project. “Even with the major environmental problems in the Lower Mekong, such as dams, forest change and overfishing, these large, charismatic species are still there and wanting to survive.”
Of course it doesn’t always work that way, said Mrs. Chea. People living along the Mekong depend on the wealth of the river for food and income. In those communities, stories abound of much larger jets chopped into small pieces to be sold in the local market, she said. In fact, Ms Chea said, another giant stingray was caught in April. However, it was already dead when they found it.
Giant freshwater stingrays aren’t the only huge and endangered creatures to be conserved along that stretch of river. It is also home to giant softshell turtles, the Mekong giant catfish, and the giant barb, a type of fish. The Wonders of the Mekong partnership is working with scientists to better understand the habitat.
Much of what is known about major rivers as ecosystems comes from the Mississippi River and rivers in Europe. But these are all in temperate regions, said Dr. Chandra. The Mekong, on the other hand, is tropical and prone to massive, seasonal flooding. This gives the Mekong a dynamic and largely unstudied ecology, he said.
dr. For example, Chandra and his team were surprised to discover recently that there were hidden pools more than 80 meters deep beneath the Mekong’s surface. If you could somehow dip the Statue of Liberty and its pedestal into one of these chasms, only the torch would remain above water.
It is likely that such pools play an important role in the life cycle of the river giants. With underwater submersibles, environmental DNA samples and sensors that can provide real-time information about changes in the river, the scientists working with the Wonders of the Mekong Project hope to learn more about these habitats and protect them from environmental threats. .
Ms. Chea has been working in these communities since 2005, developing trust and building partnerships between the project and the people who share the river with these species. And that work seems to be paying off. Now if someone accidentally brings in a giant creature, they might reach for a phone instead of a filet knife.
Ms Chea said a local leader told her he had never seen a giant freshwater stingray. And during the release, she watched as he spoke to two young boys.
She said she heard him identify the animal to them and said, “You have to protect it so that in the future your children will also know that we have a giant stingray in our village.”