The sturgeon is a prismatic, spindle-shaped fish with a head covered with bony plates and a body with 5 longitudinal rows of bony scutes. Their back is greenish-grey, more or less spotted, and their belly is yellowish or white.

Their elongated rostrum has a ventral, protractile mouth and four barbels. They use these barbels to search for prey; juveniles feed on invertebrates, while adults feed on fish such as anchovies.

They can reach up to 8 m in length, although they are usually around 2 m. The largest specimen ever caught is recorded as weighing about 3 tonnes.

It is an anadromous species, i.e. it lives in marine waters but migrates to the river to reproduce. They grow in marine waters in the Atlantic (from Morocco to the North Cape), the Caspian Sea and the Mediterranean, and later migrate to the river to spawn. This entails a considerable expenditure of energy as they have to overcome several natural and artificial obstacles. The female lays between 300,000 and 7,500,000 eggs; when they hatch, the juveniles return downstream to the sea.

They usually reproduce once every 2 to 4 years but do not reach sexual maturity until around 18 years of age.

In the past it was very common to find them in rivers when they migrated (for example in the Ebro Delta) but nowadays it is classified as a protected species, on the verge of extinction due to reservoirs, pollution and illegal fishing of juveniles.

Interesting facts

The eggs of this species are used to make real caviar, known as beluga caviar, which is the most highly prized. They were highly valued by the Romans, and in France during the Middle Ages they were known as the “King’s Fish”, for their boneless flesh, but above all for their eggs. Their swim bladder also provides an excellent glue. 

Conservation status