The beluga sturgeon can outweigh a small car and live over a century
In 1827 fishermen in the Volga estuary landed a female beluga sturgeon weighing 1,571 kilograms and stretching 7.2 metres. Nothing close to that size swims today. The world's largest freshwater fish keeps growing throughout its long life, but demand for its eggs, sold as beluga caviar, has left it critically endangered.
The beluga, Huso huso, lives mainly in the Caspian and Black Sea basins and once reached the Adriatic too. Its name, like that of the unrelated beluga whale, comes from the Russian word for white, probably for its pale flanks and belly. Among bony fish it rivals the ocean sunfish for sheer mass and is second in length only to the giant oarfish. It also competes with the great white and Greenland sharks as the biggest actively hunting fish.
Young belugas are slender with pointed snouts and feed on small bottom-dwelling creatures, turning to fish once they reach about 8 to 10 centimetres. Adults become heavy, humpbacked hunters that suck prey in at great speed. Fish make up 73% of their diet, and the largest individuals also take waterbirds and even young Caspian seals. Unlike most sturgeons, the beluga hunts in open water rather than grubbing along the bottom.
Like salmon, belugas leave the sea to breed in rivers, laying sticky eggs on gravel. Some once travelled 1,000 kilometres upriver, but dams now block most historic routes. Males mature at 12 to 16 years and females at 16 to 22, and they spawn only every four to seven years. That slow pace makes the species acutely vulnerable: a fish reportedly capable of passing 100 years in the wild is now rarely recorded beyond 56.
Mature fish caught today generally weigh 19 to 264 kilograms, a fraction of the historic giants. Within the European Union only the Danube still holds naturally breeding sturgeon. The species is protected under the Bern Convention, its trade is restricted by CITES, and the United States has banned imports of Caspian beluga caviar since 2005. Its swim bladder once yielded the finest isinglass.
Source: Beluga (sturgeon)
