Fishermen in the Stung Treng region of northern Cambodia made a historic catch on 13 June 2022 when they hauled in the largest freshwater fish to ever be officially recorded.
The female giant freshwater stingray (Urogymnus polylepis) weighed approximately 300 kg (661 lb) – about the same as a typical grizzly bear – and had a total length of 3.98 m (13 ft) with tail included, making her longer than a pickup truck!
The phenomenal fish, also known as a whipray, spanned 2.2 m (7 ft 2 in), meaning that if she were placed on a ping-pong table, her outer "wings" would overhang each side by a foot (30 cm).
The record-breaking ray, which is an endangered species, was named Boramy ("full moon" in the Khmer language), owing to both her rounded disc-like shape and the early-evening time of her release.
Although discovered by locals, the measurements were taken by a team of international ichthyological experts working as part of the US-Cambodian "Wonders of the Mekong" project, in collaboration with the Cambodian Fisheries Administration.
Fisheries biologist Dana Lee, of FISHBIO, was among the scientists who helped to measure this river monster.
"Catching the first glimpse of the giant stingray as it was pulled from the depths was a magical moment for me," he told GWR.
"The Mekong has always been somewhat of a mythical place in my mind and this creature almost seemed like the river personified."
"The size, grace, strength and wild energy of the animal was unlike anything I’ve ever experienced." – Dana Lee, fisheries biologist
This was echoed by giant fish expert Dr Zeb Hogan, who presents the TV series Monster Fish but also serves as director of the "Wonders of the Mekong" initiative.
"This is an absolutely astonishing discovery and justifies efforts to better understand the mysteries surrounding this species and the incredible stretch of river where it lives."
"In 20 years of researching giant fish in rivers and lakes on six continents, working with hundreds of local scientists and fishermen, this is the largest freshwater fish that we’ve encountered or that’s been documented anywhere worldwide." - Dr Zeb Hogan, Wonders of the Mekong Director
"While fishermen in Cambodia tell stories of stingrays up to 500 kg [1,100 lb], we've never been able to verify these reports. It's very fortunate that the 'Wonders of the Mekong' team was on site, that the fishermen called us, and that the stingray was tagged and released."
This isn’t the first record-breaker to emerge from the mysterious, little-explored waterways of mainland south-east Asia.
The previous largest freshwater fish specimen was a Mekong giant catfish (Pangasianodon gigas) found in another stretch of the Mekong River – that time in Thailand – in June 2005. It tipped the scales at 293 kg (646 lb) and measured 2.7 m (8 ft 11 in) from head to tail.
The Mekong giant catfish and the giant freshwater stingray now share the record for largest freshwater fish species as it’s currently too close a call to award it to just one.
They are frontrunners in a surprisingly crowded field.
Other contenders include a closely related catfish known as the paroon shark, otherwise known (more ominously) as the dog-eating catfish (Pangasius sanitwongsei). This behemoth bottom-feeder shares a similar geographic range to its cousin the Mekong giant, and is believed to grow to similar prodigious sizes.
Outside south-east Asia, South America’s arapaima (Arapaima gigas) is believed to attain a greater length than the Mekong’s megafish – up to 4.5 m (14 ft 9 in) – but weighs significantly less, in the region of 200 kg (440 lb).
A former prime contender, the Chinese paddlefish (Psephurus gladius), once native to the Yangtze River Basin, grew to a confirmed length of 3 m (9 ft 10 in) and also weighed c. 300 kg (661 lb) – although much larger, uncorroborated specimens have been reported as long as 7 m (23 ft) and weighing 450 kg (990 lb)!
However, in 2020, this species was officially declared extinct, likely to have died out sometime between 2005 and 2010 owing to overfishing and habitat loss. This means it currently holds the unenviable record of the most recent freshwater fish extinction.
Historically, another freshwater fish that may have taken the crown is the European catfish, or wels (Silurus glanis). Russian specimens in the 19th century were reputed to attain lengths of 4.6 m (15 ft) and weights of 336 kg (720 lb) – but today anything over 1.8 m (6 ft) and 90 kg (200 lb) is considered large.
Boramy the super-sized stingray has reignited national pride in the region’s extraordinary wildlife and the vital need for conservation efforts.
"This historic event highlights the success of USAID’s 'Wonders of the Mekong' project," said USAID/Cambodia Acting Mission Director, Hanh Nguyen.
"Cambodia is blessed with incredible biodiversity and we are proud of the team’s efforts to promote sustainable management and raise public awareness on the important role of the Mekong River."
According to Dr Hogan, this superlative stingray offers a glimmer of hope for other under-threat megafish.
"It's a reason for optimism. It's a hopeful sign. And it's a signal to us that it's not too late to protect the Mekong River."
"I hope that this catch raises awareness about the extraordinary animals that live in the Mekong River, the river's globally significant fisheries, and the importance of a healthy Mekong River to millions of people in Thailand, Laos, Cambodia and Vietnam."
Before the giant fish was released back into the river, an acoustic tag was fitted for the first time to one of these rays, so scientists can hopefully learn more about this species’ movements, which for so long have remained as murky as the muddy waters they inhabit.
"We would like to learn about the ecology and migration patterns of the species," Dr Hogan said. "Why is it found in the area? What is its home-range size? Is it a sedentary or migratory species? This information can be used to develop a conservation plan."
Dr Hogan and journalist Stefan Lovgren have a book about their search for the world's biggest freshwater fish, titled Chasing Giants (University of Nevada Press), slated for release in April 2023.
You can learn more about the "Wonders of the Mekong" project by searching for @mekongwonders on Facebook, YouTube and Instagram.
Image and video credit: Wonders of the Mekong, FISHBIO, Sinsamout Ounboundisane, Chea Seila, Doug Demko, Chhut Chheana