The aquatic life of our planet is as extensive as it is amazing. Although we tend to associate freshwater fish with small, peaceful species, the reality is that many rivers and lakes are home to true giants. These magnificent creatures have fascinated scientists and fishing enthusiasts alike with their colossal size and biological peculiarities, occupying a privileged place among the largest and most amazing species in the entire animal kingdom.
In this article, you will discover What are the largest freshwater fish in the world?, their unique characteristics, habitats, interesting facts, and how human activity has affected these river titans on different continents. Get ready to get up close and personal with these aquatic giants and understand the importance of preserving their presence in our ecosystems.
Giant freshwater stingray: the colossus of the Mekong
La giant freshwater ray (Urogymnus polylepis), also known as the giant whip, has earned the title of largest freshwater fish ever documented after a historic capture in the Mekong River, Cambodia. Recently, a female specimen of 3,98 meters long and 2,2 meters wide, with a weight of around 300 kilograms, was found and released after being scientifically studied.
This species is found in large rivers and estuaries in Southeast Asia and Borneo. It lives on sandy and muddy bottoms, where it feeds primarily on small fish and invertebrates. Its impressive size and characteristic, almost circular shape have made it one of the great enigmas of river fauna. In local culture, this specimen was named "Boramy," meaning "full moon," due to its round shape and the time of capture.
Beluga sturgeon: the European and Asian giant
El beluga sturgeon (Whoso whoso) is considered by many experts to be the largest and heaviest freshwater fish in the world, reaching more than 4,5 meters in length and exceeding 1100 kilograms in weight in documented casesThis species lives mainly in the Caspian and Black Sea basins, extending along rivers such as the Volga, the Danube and tributaries in eastern Europe and western Asia.
Sturgeons stand out for their evolutionary antiquity, with fossil remains dating back more than 250 million years. Its appearance is unmistakable, with a elongated, robust body, short snout, wide mouth and sensory barbels which it uses to detect prey on muddy or stony bottoms. Its color varies from leaden gray on the back to a white or creamy belly, although it can darken depending on age and habitat.
One of the great attractions of the beluga sturgeon is the caviar, obtained from its roe, a product in high demand in international gastronomy. This commercial pressure, combined with the construction of dams and river pollution, has led the species to a state of critical danger according to the IUCN Red List. To learn more about these fish, we recommend visiting our section on prehistoric fish.
In addition to the beluga, there are other notable species such as the white sturgeon (Acipenser transmontanus), which lives in North America and can reach 6 meters long and up to 816 kilograms, one of the largest in the Western Hemisphere. White sturgeon have survived for tens of millions of years, but currently face serious risks of extinction due to habitat loss and overfishing.
Mekong giant catfish
El Mekong giant catfish (Pangasianodon gigas) is another of the aquatic titans that inhabit the mighty rivers of Southeast Asia. This colossus can reach 2,7 meters long and a weight close to 300 kilogramsThe largest specimen on record weighed 293 kilograms and was caught in the Thai waters of the Mekong River.
These large catfish have a robust, scaleless, silvery-grey body and a broad, flat head. They are herbivores They feed primarily on phytoplankton, algae, and plant debris, unlike other giant fish, which are predominantly carnivorous. The conservation of species like this is essential to maintaining the balance of their ecosystems.
PiraÃba: the monster of the Amazon
La PiraÃba (Brachyplatystoma filamentosum) is he The largest catfish in South America and one of the most formidable predators in the Amazon basin. Its body can reach up to 3,6 meters long and weighing more than 200 kilograms, although the usual average is somewhat lower.
It is characterized by a huge mouth, capable of opening up to 40 centimeters, which allows it to swallow large prey, including other fish, snakes, birds, small mammals, and even monkeys. Accounts from native fishermen and scientific studies concur in its voracious and opportunistic behavior.
The PiraÃba emits a growl-like sound when threatened, which distinguishes it from other large Amazonian fish. It's a prized species in sport and commercial fishing, but its size and strength make it a challenge even for the most experienced.
Arapaima: the king of the Amazonian rivers
El Arapaima (arapaima gigas), also know as paiche or pirarucu, stands out for its prehistoric appearance and for being one of the longest freshwater fish that exist, reaching to measure more than 3 meters long and weigh up to 250 kilograms.
Lives in rivers, lakes and flooded areas of the Amazon basin, adapting to oxygen-poor waters thanks to its ability to breathe atmospheric air through a highly developed swim bladder that functions as a primitive "lung." This adaptation allows it to survive in environments with low oxygenation, especially during the dry season, when many species fail to survive.
La appearance of the arapaima It is unmistakable: its elongated body, large scales with golden iridescence and reddish specks, and a reddish caudal and dorsal fin. Its enormous mouth points upward, and its bony tongue has traditionally been used in Amazonian medicine, as well as for making tools and crafts.
Giant catfish: the predator of European rivers
El European catfish (Silurus glanis), also known as wels catfish, is the largest freshwater fish in Western Europe. It can reach the 3 meters and weigh up to 127 kilograms, being common in large rivers such as the Po, the Danube and the Ebro.
Its elongated body, the absence of scales and the wide mouth adorned with sensory barbels make this fish an efficient hunter, specialized in capturing de peces, aquatic birds, and even small mammals. Some documented specimens have been true record holders, and their presence causes a sensation every time one of these giants is caught.
Mangar and other giant species of the Old World
El eat (Northern Pike Luciobarbus esocinus) is a fish little known outside the Tigris-Euphrates region, but is distinguished as the largest freshwater fish in Türkiye, reaching records of up to 111 kilogramsIts appearance resembles that of a giant barbel, with large jaws and a predatory attitude. Although not as massive as sturgeon or giant catfish, it is an example of the extraordinary diversity of Eurasian rivers.
Other American giants: the alligator gar
In North America, in addition to the white sturgeon, the alligator gar (atractosteus spatula), known as the crocodile fish. This fish can measure more than 3 meters long and weigh up to 130 kilogramsIts crocodile-like appearance, with a fish-like body and two rows of sharp teeth, makes it a dominant predator in rivers and lakes in the southeastern United States and Mexico.
The alligator gar is famous not only for its size, but also for its ability to breathe air and survive out of water for hours, taking advantage of swampy and low-oxygen environments.
Human impact and conservation of river giants
The future of these freshwater giants It is closely related to the conservation of aquatic ecosystems. Overfishing, dam construction, pollution, and illegal trade are the main threats to the survival of these species. Many of them, such as the beluga sturgeon, the Mekong giant catfish, and the giant freshwater stingray, are critically endangered and could disappear if effective conservation measures are not taken.
Conserving these fish involves promoting sustainable fishing, restoring river habitats, implementing breeding programs and releasing captive-born specimens, as well as raising awareness about the ecological and cultural value of these impressive animals. To learn more about the importance of conservation, you can read our article on the wealth de peces in aquatic ecosystems.
The existence de peces These enormous freshwater creatures are a testament to the natural wealth of our rivers and lakes. Admiring these giants, from the Mekong stingray to the beluga sturgeon and the arapaima, invites us to reflect on the importance of preserving freshwater habitats for future generations. Their presence is not only a testament to animal evolution and adaptation, but is also critical to maintaining the biodiversity and ecosystem services on which we depend.
