The title of biggest fresh water fish in the world is currently held by Huso huso, the European sturgeon. Also known as the Beluga, the largest recorded of this species was a female measured in 1827 at a length of 24 feet (7.2 meters) and a weight of 3,250 pounds (1,476 kilograms). Female belugas are usually 20% bigger than male specimens.
An anadromous species of fish (meaning that they live mostly in the ocean, but breed in fresh water), the beluga belong to the Acipenseridae sturgeon family of the Acipenseriformes order. Not to be confused with the Beluga whale, the sturgeon beluga takes its name from the Russian word “belyy,” which means “white.” These fish are mainly found in the basins of the Caspian and Black Sea, though they can sometimes be found in the waters of the Adriatic Sea.
Belugas are a predatory species that preys on other fish. Travelling upstream to spawn in rivers, these sturgeons are occasionally equated with sea fish, although they are considered by a majority of scientists as river fish. With a slow rate of growth and a very late maturation process, the beluga is known to live for as long as 118 years of age, growing ever larger as they grow even older.
Belugas, the females in particular, have been sought after for their roe (internal ovaries), a key ingredient in making caviar. Due to poaching and over fishing, the beluga has had to endure a significant depletion in their numbers, which prompted several governments to enforce restrictions on their trade. In recent times, beluga specimens that have been caught usually range in size from 4.66 to 10.76 feet (142 to 328 centimeters) in length and 42 to 580 pounds (19 to 264 kilograms) in weight.
Because sturgeons spend part of the time in sea water, there are those who question the veracity of the beluga’s claim to being the world’s biggest fresh water fish. Another contender was the similar sturgeon species Huso dauricus, the River Beluga. Also known as the Kaluga, it is smaller than the beluga, but still large at a length of 18.6 feet (5.6 meters) and a weight of 2,205 pounds (1,000 kilograms). But like the beluga, it too partially lives in salt water. Those who reject the beluga consider Pangasianodon gigas, the Mekong giant catfish, as the true biggest fresh water fish. Indigenous to Southeast Asia’s Mekong basin, it has been listed in the Guinness Book of World Records for reaching up to 10.5 feet (3.2 meters) and 660 pounds (300 kilograms) in size.