On the night of June 13, 2022, near Koh Preah island, in northern Cambodia, a Mekong fisherman caught a female ray weighing 300 kg. The biologists from the Wonders of the Mekong project weighed it and then released it with a transmitter.
No freshwater fish this heavy had been weighed before.
This figure challenges the rankings in circulation, including the previous version of this page. It listed 1,500 kg for a sturgeon, 7 m for a paddlefish, and 5 m for a wels catfish. So we reviewed each record with two questions. Was the weight measured? Does the fish really live in freshwater?
What is the largest freshwater fish ever weighed?
The giant freshwater ray (Urogymnus polylepis) holds the documented record: 300 kg for about 4 m long, including the tail, measured in June 2022 in Cambodia. It surpasses the Mekong giant catfish of 293 kg caught in Thailand in 2005, which held the title for seventeen years.
The key word here is “documented.”
The FishBase entry for the species reports a maximum published weight of 600 kg, double the record weighed in Cambodia. No dated weighing accompanies it in recent reports we consulted. We keep it as an estimate. But the 2022 female was weighed and measured by a scientific team, which changes everything for a record. The IUCN classifies it as endangered (2021 assessment).
The team from the University of Nevada at Reno, leading the project with USAID funding, reminds that populations of giant freshwater fish have declined by nearly 90% in forty years.
Is the beluga a freshwater fish?
Not strictly. The beluga (Huso huso) is anadromous: it grows up in the Caspian Sea or the Black Sea, then swims up rivers to reproduce. The IUCN attributes up to 8 m and 1,700 kg to it, sizes reached by a fish that spends most of its adult life in the sea.
Ranking it first in a freshwater list therefore compares two different worlds.
Yet almost all top lists do this. Sturgeons are caught in rivers, where they are seen swimming up the Volga or the Danube. Old figures also cloud the reading. FishBase cites a maximum published weight of 3.2 tons and an age of 118 years for the beluga. No one can verify these values today.
The status, however, is beyond doubt. The beluga is critically endangered (CR) on the Red List, a classification confirmed by the IUCN update of July 21, 2022, which considers the 26 remaining sturgeon species threatened with extinction.
And the white sturgeon?
The same logic. The white sturgeon (Acipenser transmontanus) of the North American Pacific is also anadromous. FishBase gives it a maximum of 6.10 m and 816 kg, and a vulnerable status (VU, 2020 assessment).
Which giants spend their entire lives in freshwater?
The Mekong giant catfish, the Amazon arapaima, and the North American alligator gar live in freshwater from start to finish. The Mekong catfish migrates within the basin without reaching the sea, what biologists call a potamodromous fish.
Start with the Mekong giant catfish (Pangasianodon gigas). The 293 kg specimen caught in Thailand in 2005 remains the reference, and FishBase indicates a maximum length of 3 m which it itself considers to be confirmed. The species has been critically endangered (CR) since the 2011 IUCN assessment, and its international trade is banned by CITES. The figure of “nearly 300 kg” from the old article was therefore credible for this species, unlike most other values. However, this record should not be read as a common size.
The arapaima (Arapaima gigas) poses another problem. Rankings often list 3 m and 300 kg, figures not supported by reference databases. FishBase retains 200 kg as the maximum published weight and 2 m as the common length, and its IUCN status dates from 1996 with the note “data deficient,” an assessment too old to judge the current state of populations. It must surface to breathe air.
The alligator gar, finally, tops out at 2.60 m and 137 kg according to FishBase, far from the 320 kg of the previous version.
Does the bull shark count?
No. This marine shark tolerates freshwater and swims up some rivers, but it mostly lives in the sea. We removed it from the ranking. Our selection of the strangest sharks in the world presents other surprising cases.
What happened with the Chinese paddlefish?
The Chinese paddlefish (Psephurus gladius) was declared extinct by the IUCN in its update of July 21, 2022. The last confirmed living individual was seen in 2003 in the Yangtze River, and a study published in 2020 places its disappearance between 2005 and 2010.
The main cause has a name: the Gezhouba Dam, in operation since 1981.
It blocked the migration route to spawning areas, and adults could no longer reproduce. The population aged without being replaced. Then it disappeared. Thus, when the IUCN officially declared the extinction, the species had not reproduced for years. The same update moved the Yangtze sturgeon into the “extinct in the wild” category, as the fish still present in the river come from hatcheries.
What remains is the size. The 7 m and 1,500 kg from the old article are not based on any solid measurement. Confirmed specimens exceeded 3 m, and the last live female captured measured 3.52 m for about 160 kg.
What size does the wels catfish reach in France?
The wels catfish (Silurus glanis) maxes out around 2.8 m in documented records. The French record, validated on video, was caught in the Tarn in June 2025: 2.75 m for about 150 kg estimated. The world record for sport fishing belongs to the Po River in Italy, with 2.85 m in May 2023.
The 5 m and 330 kg from the old table should therefore be forgotten.
FishBase gives 2.73 m and 130 kg as published maximums, and the IUCN classifies it as least concern (LC, 2022 assessment), with a native range covering much of Europe and western Asia. The species has been widely introduced and relocated across the continent, hence its presence in many French rivers. Large wels catfish are not always weighed to avoid injuring them. Therefore, French records are expressed in length. The Tarn provides an example: in 2025, successive measurements gave 2.77 m then 2.70 m before the video validation at 2.75 m.
If you dive in a lake or river, you might encounter one. Nothing guarantees it. Keep your distance and let it go, the same reflexes as those detailed in our article on why you should never touch marine life.
What ranking to adopt in 2026?
Keeping only fish that live in freshwater and weighed records, the giant freshwater stingray tops the list with 300 kg, ahead of the giant Mekong catfish (293 kg). Anadromous sturgeons are heavier, but they play in another category. Here is the corrected table, with for each species its habitat and an IUCN status dated by the year of assessment.
| Species | Record or published maximum | Habitat | IUCN Status (year of assessment) |
|---|---|---|---|
| Giant freshwater stingray | 300 kg, about 4 m (Cambodia, 2022) | Fresh and brackish water | Endangered, EN (2021) |
| Giant Mekong catfish | 293 kg (Thailand, 2005) | Freshwater, potamodromous | Critically endangered, CR (2011) |
| Arapaima | 200 kg published, 2 m common length | Freshwater | Data deficient, DD (1996) |
| Alligator gar | 137 kg, 2.60 m | Freshwater, rarely brackish | Least concern, LC (2018) |
| Wels catfish | 2.85 m (Italy, 2023) | Freshwater | Least concern, LC (2022) |
| Beluga | Up to 8 m and 1,700 kg according to the IUCN | Anadromous | Critically endangered, CR (confirmed in 2022) |
| White sturgeon | 6.10 m, 816 kg | Anadromous | Vulnerable, VU (2020) |
| Chinese paddlefish | More than 3 m confirmed | Yangtze, migratory | Extinct, EX (2022) |
It has its limits.
However, it avoids two common pitfalls. The first is mixing a weighed weight and a fisherman’s estimate. The second is putting a river fish and a sea fish that migrates upriver to spawn in the same list, which almost all rankings copied from one site to another do (and the old version of this page too, we admit it). Records change quickly. A new specimen could dethrone the stingray tomorrow.
Longevity holds other surprises, and our ranking of the longest-living marine animals makes the same distinction between measured figures and legends. In terms of appearance, the Mekong giants have nothing to envy from the ugliest fish in the world, and the ray has a venomous sting that places it among the extraordinary defense mechanisms in marine animals.
FAQ
What is the largest freshwater fish in the world?
The documented record belongs to a giant freshwater ray weighing 300 kg, caught in Cambodia in June 2022 by the Wonders of the Mekong project team. It surpasses the giant Mekong catfish of 293 kg caught in Thailand in 2005.
Is the beluga bigger than the Mekong ray?
Yes, the IUCN attributes up to 8 m and 1,700 kg to it. But the beluga is anadromous: it lives in the sea and swims up rivers to spawn.
Does the Chinese paddlefish still exist?
No. The IUCN declared it extinct in July 2022. The last confirmed living individual dates from 2003, and a 2020 study estimates it disappeared between 2005 and 2010, after the construction of the Gezhouba dam.
Sources
- Migratory monarch butterfly now Endangered – IUCN Red List (IUCN, 2022)
- World’s largest freshwater fish found, released in the Cambodian Mekong River by Global Water Center team (University of Nevada, Reno, 2022)
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Photo: Ad Meskens, Wikimedia Commons, CC BY-SA 4.0
