Beluga Sturgeon

The beluga sturgeon (Huso huso) is one of the largest freshwater and anadromous fish in the world, native to the Caspian Sea and Black Sea basins of Eurasia. It belongs to the family Acipenseridae and the genus Huso, which is distinguished from other sturgeon genera by a larger mouth and more predatory feeding habits as an adult. Beluga sturgeon can live for many decades and grow to enormous size, with historical records describing individuals well over five meters long. Like other sturgeon, it is anadromous, migrating from the Caspian and Black Seas into large rivers such as the Volga, Ural, and Danube to spawn. The species is classified as critically endangered due to river damming, habitat loss, and decades of overexploitation.

Beluga sturgeon are exceptionally large, with adults commonly measuring 2-4 m and historical records exceeding 5-7 m.

• Body: massive and elongated, with five rows of large bony scutes along a pale gray to bluish-gray body
• Head: broad, shark-like head with a comparatively short, blunt snout and thick barbels
• Mouth: notably large and crescent-shaped compared to other sturgeon, reflecting its more predatory, fish-eating diet as an adult
• Tail: asymmetrical, heterocercal tail with an elongated upper lobe

Its combination of enormous size, pale coloration, and unusually large mouth separates it from other Caspian and Black Sea sturgeon species, which are generally smaller with narrower mouths.

Beluga sturgeon are native to the Caspian Sea and Black Sea basins, where they spend most of their adult lives in open brackish water before migrating into large connecting rivers such as the Volga, Ural, Danube, and Dnieper to spawn. They favor deep, open water as adults and require long stretches of free-flowing river with gravel or rocky substrate for successful spawning migrations. Because much of their historical river range has been fragmented by dams, remaining spawning migrations are now largely restricted to a handful of major river systems, and the species' overall range has contracted significantly compared to historical records.

Beluga sturgeon are slow-growing and exceptionally long-lived, with females not reaching sexual maturity for well over a decade and total lifespans potentially exceeding a century. Unlike most other sturgeon, which feed mainly on invertebrates, adult beluga sturgeon are active predators of other fish, using their large mouth to capture prey in open water. Adults undertake long migrations from the Caspian and Black Seas into major rivers to spawn over gravel beds, a journey now hampered across much of their range by dams and river regulation. Due to their slow reproductive cycle and history of intensive commercial exploitation, wild populations have declined severely and are subject to international conservation measures.