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Boramy, a female giant freshwater stingray, is the best-documented answer to the question of what is the largest river fish ever recorded. Local fishers caught her in Cambodia’s Mekong River on June 13, 2022. Researchers measured her at approximately 300 kilograms (661 pounds) and 3.98 meters (about 13 feet) from snout to tail, with a disc width of roughly 2.2 meters.
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That makes Boramy the largest reliably measured fish specimen known from a wholly freshwater or fresh-and-brackish-water life history. The qualification matters: this is not a claim that no fish connected with rivers—including migratory species that also spend part of their lives in the sea—could ever be heavier.
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Boramy was a giant freshwater stingray, a cartilaginous fish whose flattened body formed a broad, rounded disc. At approximately 2.2 meters wide, her body was wider than many small boats. Her total length, including the long tail, was just short of four meters.
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The research team named her Boramy, a Khmer word translated in project and news coverage as “full moon.” The name referred to her rounded shape and the moon visible around the time she was released.
| Measurement | Recorded figure |
|---|---|
| Species | Urogymnus polylepis |
| Sex | Female |
| Weight | Approximately 300 kg (661 lb) |
| Total length | 3.98 m (about 13 ft), from snout to tail |
| Disc width | Approximately 2.2 m |
| Location | Upper Mekong River near Stung Treng, Cambodia |
| Capture date | June 13, 2022 |
How Boramy became the record holder
Local fishers caught the ray in the upper Mekong in northeastern Cambodia and alerted researchers. Teams from Cambodia’s Fisheries Administration and the Wonders of the Mekong project arrived to document the animal, take measurements, and coordinate her release.
Boramy was released into the river on June 14, 2022, after the examination. Researchers fitted an acoustic tag near the base of her tail before returning her to the Mekong. The tag allowed underwater receivers positioned in the river to register her movements.
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Is a stingray really a fish?
Yes. Stingrays are cartilaginous fishes, related to sharks and skates. Their skeletons are made primarily of cartilage rather than bone, but they are fish in biological terms. A giant freshwater stingray can therefore be compared with a Mekong giant catfish in a record for freshwater fish.
Boramy’s record has a second important boundary: the comparison concerns fish that spend their lives in fresh or brackish water. It should not be broadened into “the largest fish ever” or “the largest fish that has ever lived in a river.” Some very large fish use rivers during migration but also spend part of their lives in the sea, making them a different comparison.
What species was Boramy?
Boramy belonged to the giant freshwater stingray species Urogymnus polylepis. Older reports may identify the same species using the scientific combination Himantura chaophraya. That older name remains visible in earlier articles and research materials, but Urogymnus polylepis is the name to use here.
The species is not simply a large aquarium curiosity. Conservation sources classify the giant freshwater stingray as endangered. Large river animals are particularly vulnerable to fishing pressure and to changes in the connected river habitats they need, including deep pools, channels, seasonal migration routes, and floodplain environments.
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Why scientists tagged the giant ray
The acoustic tag turned an extraordinary capture into a rare research opportunity. Receivers in the Mekong could detect the tag when Boramy passed nearby, allowing researchers to study where she moved during the monitoring period.
Peer-reviewed tracking research reported detections across multiple receivers and a relatively small observed home range during that period. That result should be interpreted carefully. It describes the movements observed for Boramy under the conditions and time span of the study; it does not establish that every giant freshwater stingray has the same home range or stays in the same areas.
Even limited movement data can help researchers ask practical conservation questions: Which deep pools or channels do large rays use? Do individuals repeatedly return to particular areas? How might fishing activity, river engineering, or altered seasonal flows affect them? Identifying those patterns may help conservation planners determine which habitats deserve closer protection, although the tag alone does not prove that any specific management measure has succeeded.
The Mekong is still under pressure
The Mekong is one of the world’s major freshwater systems and supports an exceptional variety of fish, including some of the largest species on the planet. Its giant fish depend on a functioning network of river channels, deep pools, seasonal movements, and productive floodplains. The importance of each habitat varies by species and by section of the river.
Boramy’s discovery therefore carries a message that is both encouraging and troubling. It shows that an extraordinary endangered river animal still existed in the Mekong in 2022. It does not show that the entire river is healthy or that the species is secure. A record-size individual and a threatened population can exist at the same time.
Readers who want broader context on the pressures facing the river may find Last Days of the Mighty Mekong by Brian Eyler useful as a book about the Mekong’s ecological crisis. It provides wider ecological and human context rather than serving as a stingray identification guide.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the release matters
Catching a fish of this size could easily have ended as a record photograph and a dead specimen. Instead, researchers documented Boramy, attached a tracking device, and returned her to the river. That made it possible to learn from a living animal while avoiding the loss of an endangered megafish.
There is no basis for claiming a long-term survival outcome beyond the tracking evidence that has been reported. The defensible conclusion is narrower but important: Boramy was caught, measured, tagged for movement research, and released alive into the Mekong.
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The bottom line
Boramy was an approximately 300-kilogram female giant freshwater stingray, nearly four meters long including her tail. Her measurements made her the largest reliably measured fish known to remain in fresh or brackish water, surpassing the earlier 293-kilogram Mekong giant catfish record.
Her significance goes beyond size. The fact that she was returned to the Mekong with an acoustic tag gave scientists rare information about an elusive endangered species—and a chance to better understand the river habitat that giant freshwater stingrays need.
Frequently Asked Questions
What was the largest river fish ever recorded?
Boramy was an approximately 300-kilogram female giant freshwater stingray, or Urogymnus polylepis, caught in Cambodia’s Mekong River in June 2022.
How much did the largest recorded river fish weigh?
Approximately 300 kilograms, or about 661 pounds. Because the figure is an approximate measurement, it should not be presented as a precisely established weight.
Was Boramy released after she was caught?
Yes. Researchers fitted her with an acoustic tag near the base of her tail and released her into the Mekong on June 14, 2022. The tag was used to study her movements; the available evidence does not establish her long-term fate.
What fish held the freshwater record before Boramy?
The earlier comparable record belonged to a 293-kilogram Mekong giant catfish caught in Thailand in June 2005.
The Bottom Line
Boramy was the largest reliably measured freshwater-fish specimen on record: an approximately 300-kilogram, 3.98-meter female giant freshwater stingray caught and released in Cambodia’s Mekong River in June 2022. The record is remarkable, but the species remains endangered and the discovery should be viewed as a conservation opportunity, not an endorsement of catching threatened megafish.
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