Sturgeon are an ancient group of fish, with a lineage tracing back over 200 million years to the Jurassic period. These fish are recognized for their large size and extended lifespans. They possess distinctive physical characteristics, including elongated, spindle-like bodies covered with five rows of bony plates called scutes instead of scales. Their mouths are toothless and located on the underside of their snouts, preceded by four barbels that help them locate food along the bottom.
The Beluga Sturgeon: A Giant Among Fish
The Beluga Sturgeon (Huso huso) stands as the largest species of sturgeon and is recognized as the largest freshwater fish in the world. Historical records indicate impressive sizes, with one female captured in 1827 weighing 1,571 kilograms (3,463 pounds) and measuring 7.2 meters (23 feet 7 inches) in length. While such immense specimens are rare today due to heavy fishing, modern mature belugas typically range from 1.42 to 3.28 meters (4 feet 8 inches to 10 feet 9 inches) long and weigh between 19 and 264 kilograms (42 to 582 pounds).
The Beluga Sturgeon’s appearance changes with age; juveniles are slender with narrow heads and pointed snouts, while adults become more robust with a pronounced hump on their back. They have a shark-like tail. Their large, crescent-shaped mouth appears to “frown” in older individuals.
Life and Habitat of the Beluga Sturgeon
Beluga sturgeon are found in the Caspian, Black, and Azov Sea basins, and their associated rivers like the Volga, Danube, and Ural. They are euryhaline, moving freely between freshwater and varying saline content. This species exhibits an anadromous nature, migrating from saltwater environments into freshwater rivers to spawn. Some individuals travel over 1,000 kilometers (620 miles) upstream to find suitable spawning grounds.
Their diet is primarily carnivorous, shifting as they mature. Juveniles feed on benthic invertebrates in shallow coastal waters, becoming largely piscivorous once they reach 8 to 10 centimeters (3 to 4 inches) in length. Adult Beluga sturgeon mainly consume large fish (about 73% of their diet), but may also prey on mollusks, crustaceans, or even aquatic birds and young seals. They are the only sturgeon species known to actively eat other fish as adults.
Beluga sturgeon can live over 100 years in the wild, though human impact often shortens their average lifespan. They are late-maturing, with males reaching sexual maturity at 12 to 16 years and females at 16 to 22 years. Females typically spawn every four to seven years, laying millions of sticky eggs on clean, hard substrates such as gravel in riverbeds.
Conservation Status of the World’s Largest Freshwater Fish
The Beluga Sturgeon is currently classified as critically endangered by the IUCN Red List. This reflects a severe population decline, largely due to overfishing for their valuable roe, beluga caviar. The high demand for this delicacy has led to extensive poaching, further depleting wild stocks. Habitat degradation also poses a significant threat to the species.
Dam construction along their historical migratory routes has blocked access to essential spawning grounds, hindering natural reproduction. Pollution negatively affects habitat quality, compounding challenges. In response, conservation efforts include fishing bans and trade restrictions under CITES Appendix II. Habitat restoration projects and aquaculture programs aim to support and repopulate the species. Since 2005, the United States has banned imports of beluga caviar and other products from the Caspian Sea to discourage poaching and overfishing.