River Monsters: Discover the Biggest Fish in the Mekong River

Written by Colby Maxwell
Updated: August 29, 2023
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Key Facts:

  • The Mekong River is the twelfth longest river in the world.
  • A giant freshwater stingray caught in June 2022 is currently the record holder for the largest denizen of the river.
  • It dethroned the previous record holder, a giant Mekong catfish.

The Mekong River is a long and important river that flows through Southeast Asia, but did you know there are giants lurking beneath its waters? In fact, some of the largest freshwater fish in the entire world live in the Mekong River, although few ever see them.

The biggest fish in the Mekong River is the giant freshwater stingray.

Today, let’s discover the biggest fish caught in the Mekong River, plus learn about the other river monsters lurking below!

Where is the Mekong River?

The Mekong River is one of the most important rivers in Asia and the most important river in Southeast Asia. Over 65 million people live directly along its riverbanks and rely on it for food, transportation, and employment. Additional millions don’t live on its banks but are tied to the river through business, agriculture, and much more.

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Beginning in the Tibetan Plateau, the river then runs through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam before emptying into the South China Sea. Many of the countries it flows through use it as an important border. Overall, the river is 2,700 miles long, making it the 12 longest in the world.

What is the biggest fish in the Mekong River?

River Monsters: Discover the Biggest Fish Mekong River

The giant freshwater stingray currently holds the record for the largest freshwater fish in the world.

©Mekong on tour/Shutterstock.com

The largest fish to ever be caught in the Mekong River was a 661 lb giant freshwater stingray. While it’s true that saltwater fish are generally larger than freshwater fish, this massive catch shows just how large a true river monster can be!

“In 20 years of researching giant fish in rivers and lakes on six continents, this is the largest freshwater fish that we’ve encountered or that’s been documented anywhere worldwide…”

Zeb Hogan, Biologist – BBC

The stingray that was caught was a species known as Urogymnus polylepis, or the giant freshwater stingray. Although not commonly known, these stingrays are classified as fish and live in large rivers throughout Southeast Asia. With the most recent catch of the 661 lbs individual in June of 2022, it cements itself as the largest freshwater fish in the world, as well as the largest stingray in the world.

As a general rule, these fish can reach over 600 lbs and measure over 7 feet across. They are bottom-dwelling fish that live in muddy and sandy areas. In addition to their size, these stingrays have a sharp sting that is coated in toxic mucous. They aren’t aggressive but will strike if agitated or caught. The sharpness of the stinger and the strength of the animal allow their strikes to penetrate bones in some instances.

An endangered giant

River Monsters: Discover the Biggest Fish Mekong River

Giant freshwater stingrays are listed as endangered.

©Danny Ye/Shutterstock.com

“Finding and documenting this fish is remarkable, and a rare positive sign of hope, even more so because it occurred in the Mekong, a river that’s currently facing many challenges…”

Zeb Hogan, Biologist – BBC

As amazing as these creatures are, they are currently under threat. They are listed as endangered by the IUCN and are at serious risk. The biggest threats to the giant freshwater stingray are all human-related, particularly the overfishing and subsequent eating or selling of these amazing fish. Additionally, much of their habitat has been impacted by habitat degradation and fragmentation due to construction and pollution along the river.

Giant stingrays are primarily found in Indochina and Borneo. They live in the Mekong River Basin, the Mahakam River, and the Buket River. They had a historical range that included Sarawak and even Java, but recent studies show that they are unlikely to have survived in these regions.

What other large fish live in the Mekong River?

River Monsters: Discover the Biggest Fish Mekong River

The Mekong giant catfish could take back the lead as the largest freshwater fish in the world.

©tristan tan/Shutterstock.com

Although the giant freshwater stingray is massive, there is another contender for first place that previously held the record! Known as the Mekong giant catfish, this giant fish is only a few pounds away from once again retaking its old title.

Before the 661 lb giant freshwater stingray was caught in 2022, the previous record holder for “largest freshwater fish in the world” was the Mekong giant catfish. The largest individual to have ever been caught was measured at 646 lbs, showing just how close the competition was. These giant catfish belong to the shark catfish family and are only found in the Mekong River Basin. Before official records were kept, some reports placed the largest fish to have ever been seen at 770 lbs, although it isn’t official.

The Mekong giant catfish is at extreme risk and is listed as critically endangered by the IUCN. Spawning fish in Cambodia are being overfished, while fishermen are overharvesting them as a food source. Additionally, dams are challenging the migration of larval fish before they have the chance to grow into adults. Due this these threats, it is only found in small pockets around the middle Mekong region.

The photo featured at the top of this post is © Mekong on tour/Shutterstock.com

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About the Author

Colby is a writer at A-Z Animals primarily covering outdoors, unique animal stories, and science news. Colby has been writing about science news and animals for five years and holds a bachelor's degree from SEU. A resident of NYC, you can find him camping, exploring, and telling everyone about what birds he saw at his local birdfeeder.

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