A group of people hold the world’s largest freshwater fish, which was caught in June 2022, in a tarp.
STUNG TRENG, Cambodia — The discovery last year of a 661-pound giant freshwater stingray in Southeast Asia’s Mekong River launched an effort to understand and protect one of the largest, most mysterious creatures on the planet.
For the past 12 months, scientists have been tracking the record-breaking stingray, which after its capture in June 2022, was fitted with an acoustic tag before being released back into the river.
The data gathered has yielded surprising results: despite its enormous size, the female giant has a remarkably small home range, centered in a bio-rich but threatened stretch of the Mekong River in northern Cambodia.
This and other findings are reported in a series of studies being published this month about the giant freshwater stingray, a species that scientists know very little about but whose populations have dramatically declined across its Southeast Asian range.
The research highlights the importance of protecting the last known refuge for a menagerie of critically endangered megafish, like giant catfish, Siamese carp and seven-striped barb, as well as freshwater dolphins and giant turtles, but the site also faces potential severe environmental impacts from long-standing hydropower development plans.
While the study has provided important insights into the potential impacts of the proposed hydropower dams, conservationists have been encouraged by the Cambodian government’s recent proposal to turn the stretch of the river into a UNESCO World Heritage Site.
“This new information about the stingray and other critically endangered fish is crucial to the protection of Cambodia’s most iconic animals and the preservation of a river that provides food for millions of people,” says Zeb Hogan, a biology professor at the University of Nevada, Reno, who leads the USAID-funded Wonders of the Mekong research project that initiated the study. “The giant stingray is now at the center of a larger debate about the fate of the Mekong and how to balance river basin development with environmental stewardship so that the bountiful Mekong can continue to provide for people in the region for generations to come.”
Globally, the International Union for Conservation of Nature (IUCN) has assessed the giant stingray as endangered due to population declines as high as 79% over the last century.
In Thailand, it is listed as critically endangered due to even steeper declines and threats from fishing, pollution and habitat destruction.
An industrial chemical spill on the Mae Klong River in Thailand in 2016 is believed to have killed most of the largest stingrays found there. The stingray population in the northern Cambodia section of the Mekong, in contrast, is thought to remain relatively intact.
Scientists believe males and females co-mingle there, and the discovery of several pregnant females suggests it is an important pupping ground.
Fishers in the area have also reported catching rays weighing substantially more than last year’s record-breaking ray, a finding that’s supported by anecdotal accounts of record-breaking rays in other Asian countries.
“The detection of this giant stingray is a signal from the deep, a reminder of what’s at stake and why we need to protect river life”, said Chea Seila, program manager for Wonders of the Mekong in Phnom Penh, Cambodia. “The giant freshwater stingray is an indicator of river health. By saving the stingray, we also sustain fisheries and livelihoods. We need conservation action and cooperation between governments, local communities and scientists to protect this magnificent creature and the global biodiversity hotspot where she lives.”