Fish
Beluga Sturgeon
Huso huso · also called beluga sturgeon, great sturgeon, European sturgeon
The beluga sturgeon is a fish that can outlive a person, outgrow a rowing boat, and swim hundreds of kilometres up a river to spawn on the same gravel beds its ancestors used before the dinosaurs died out. It is also the source of the world’s most expensive caviar, and that has very nearly finished it.
Overview
The beluga sturgeon lives in the Caspian and Black Seas and migrates far up their major rivers — the Volga, Ural, Danube — to spawn. It is anadromous: adult life at sea, breeding in fresh water. Sturgeons are an ancient lineage, little changed for over 100 million years, with a cartilage skeleton, rows of bony scutes instead of scales, a shark-like tail, and a tube-like sucking mouth under the snout, preceded by four sensory barbels.
The largest river fish
Historic beluga reached 7 metres and well over a tonne — an 1827 Volga fish of 1,571 kg may be the heaviest bony fish ever recorded. Unusually for a sturgeon, adult beluga are largely fish-eaters. Growth to giant size takes a century or more, and today a beluga over 2–3 metres is a rarity; the true giants are gone.
Caviar and collapse
Beluga caviar is the most prized and expensive in the world, and demand for it drove the fish to collapse. The species was hit where it was weakest: females first spawn at 15–20 years and only every 3–4 years thereafter, and they must reach specific upriver gravel beds to do it. Then dams, especially on the Volga, cut them off from most spawning grounds, and pollution and a wave of poaching after the Soviet Union’s collapse finished the job.
Status
The beluga sturgeon is Critically Endangered. Natural reproduction has nearly ceased, and the Caspian population is now sustained mainly by hatcheries that take eggs from captured fish and release the young. International trade is tightly controlled under CITES, and legal caviar increasingly comes from aquaculture, where a first harvest still takes 15-plus years.
Beluga Sturgeon: common questions
How big does a beluga sturgeon get?
The beluga is the largest freshwater or anadromous fish in the world and one of the largest bony fish of any kind. Reliable historical records include fish of 5 to 7 metres and 800 to 1,200 kilograms, and a sturgeon caught in the Volga in 1827 reportedly weighed 1,571 kilograms, which would make it the heaviest bony fish ever recorded. Fish that size took a century or more to grow. Because the largest, oldest individuals are exactly the ones targeted for caviar, today a beluga over 2 to 3 metres is a rarity, and the giants are effectively gone.
Why is beluga caviar so expensive?
Several factors stack up. The eggs themselves are large, delicately flavoured, and produced only by mature females, which do not begin spawning until they are 15 to 20 years old. The fish is now Critically Endangered, so legal wild caviar is extremely restricted and farmed beluga caviar takes 15-plus years to produce a first harvest. And the product has a long luxury reputation. Prices of several thousand to over ten thousand US dollars per kilogram are normal, and a substantial illegal trade exists alongside the legal one.
Why did the beluga sturgeon collapse?
Overfishing for caviar is the headline cause, but it acted on a fish that was already uniquely vulnerable — one that matures at 15 to 20 years, spawns only every few years, and must migrate far up specific rivers to breed. Then dams were built across those rivers, especially on the Volga, blocking the sturgeon from most of its historic spawning grounds. Pollution, poaching after the breakup of the Soviet Union removed enforcement, and the loss of the fish's own prey compounded it. Natural reproduction in the wild has now nearly stopped, and the Caspian population persists mainly because hatcheries strip eggs from captured fish and release the young.
Are sturgeons really living fossils?
Sturgeons and their relatives the paddlefishes are an ancient branch of ray-finned fishes that appears in the fossil record over 100 million years ago and has changed relatively little since. They keep several primitive features — a skeleton made largely of cartilage, a persistent notochord, a shark-like upturned tail, rows of bony scutes instead of scales, and a toothless, protrusible, tube-like mouth on the underside of the snout, with four sensory barbels in front of it used to detect food on the bottom. Like other "living fossils," they have of course continued to evolve, but the body plan is recognisably old.