SCIENCE LAB SPECIAL : CAMBODIA

Rescue Party

For a Mekong River colossus, a little help from its friends.

Just after dawn on May 5, scientists working along a stretch of the Mekong River in Cambodia released a giant endangered freshwater stingray that had been caught on a fisherman's line.

At 13 foot long and 400 pounds [181 kilograms] the stingray was larger than a hibachi table.

''It was shaking, and I told her, 'Calm down, we will 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 stingray species, also known as a whipray. With dusky-brown tops and creamy white bottoms, the animals slide across riverbeds in search of fish and invertebrates.

They can grow to epic proportions, but the animals have become endangered through overharvesting for the stingray's meat, accidental deaths in fishing nets, and habitat fragmentation and degradation from dams, pollution and other human activities.

After receiving a call from a fisherman who caught the stingray, Ms. Chea and her team drove for eight hours to assist with the release. They arrived at 3 a.m. and waited the fish until the sun came up. Many people were needed to delicately move the animal, which was warmed with a venomous barb that could do more than a foot long and is capable of piercing bone.

Before freezing the stingray, Ms. Chea and her colleagues took noninvasive samples that would help with future study of the species. They then helped guide the colossus back to the Mekong's depths.

''She swam away calmly, but then appeared again, which made us feel so, so happy,'' Ms. Chea said.

That a stingray of this size could still be found in these waters was extraordinary, the experts said.

''It shows you nature is so beautiful but also resilient,'' said Sudeep Chandra, a limnologist at the University of Nevada Reno and a scientist on the Wonders of the Mekong Project.

''Even with the major environmental problems in the Lower Mekong, like dams, forest change and overfishing, these large, charismatic species are still there, wanting to persist.'' [ Jason Bittel ]