The giant Mekong catfish was once at the top of the list of the largest freshwater fish, but today that position belongs to the beluga sturgeon.
Sturgeons (Acipenseridae) are called “living fossils” because they appeared on Earth over 250 million years ago. Of the 27 existing species of this family, the beluga sturgeon (Huso huso) is the largest representative.
In 1827, a Beluga sturgeon captured at the mouth of the Volga reached 7.2 m long and weighed 1,571 kg, the equivalent of an adult great white shark. It is the largest specimen ever recorded to date.
According to the International Union for the Conservation of Nature (IUCN), the beluga sturgeon can live more than 100 years in the wild. When they reach their maximum size, they become top predators, feeding mainly on large fish like carp and salmon. This species sometimes hunts mollusks, waterfowl, young seals and other species of sturgeon.
Their long lifespan and aggressive hunting properties are two of the reasons beluga sturgeon can grow to such a large size, says expert Phaedra Doukakis of the National Oceanic and Atmospheric Administration. USA (NOAA) told Live Science.
However, today most sturgeons cannot exceed 3.5 m in length. This is due to the pressure of overfishing, which has made tall and elderly individuals increasingly scarce in recent decades.
Although classified as a freshwater fish (because they hatch in river spawning grounds), the adult beluga sturgeon spends a lot of time in both salt and brackish water. This is why they were not previously recognized as the largest freshwater fish in the world. This title once belonged to the giant Mekong catfish (Pangasianodon gigas), a “pure freshwater” fish in Southeast Asia. They can be over 3 m long and weigh 150 to 350 kg.
These two giant fish are now considered “critically endangered” in the IUCN Red List. Besides the threat of overfishing, the construction of dams on rivers also disrupts their habitat and reproduction.
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