Based on the world record nomination from World Records Institute (WRI) and Decision No. WK/USA.INDIA/853/2022/No.309, World Records Union (WorldKings) officially declared Beluga sturgeon as the world’s largest freshwater fish on May 28th, 2022.
The beluga, also known as the beluga sturgeon or great sturgeon (Huso huso), is a species of anadromous fish in the sturgeon family (Acipenseridae) of order Acipenseriformes.
The beluga is a species of sturgeon that inhabits portions of the Black Sea and the Caspian Sea. Because they continue to grow throughout their lifetime (which can be 100 years), the beluga might be the world's largest freshwater fish. Some of the largest belugas discovered have been nearly 7.2 m long and weigh more than 1,500kg —numbers that also put them in contention for being the largest bony fish in the world by mass.
The largest accepted record is of a female taken in 1827 in the Volga estuary at 1,571 kg and 7.2 m. Another specimen reportedly weighed 1,220 kg and measured 6.1 m in length. Several other records of aged sturgeon exceed 5 m. Among sturgeons, only the closely related Kaluga (Huso dauricus) can attain similar size, with a maximum weight of 1,000 kg.
Beluga of such great sizes are very old (continuing to grow throughout life) and have become increasingly rare in recent decades because of heavy fishing of the species. Today, mature belugas that are caught are generally 142–328 cm long and weigh 19–264 kg. The female beluga is typically 20% larger than the male. An exceptionally large beluga recently caught weighed 960 kg and measured 3.4m.
According to treehugger.com; en.wikipedia.org.