Acipenser güldenstädti

Russian sturgeon / Danube sturgeon (A. güldenstädti). Photo credit: Vasile Oţel – Danube Delta National Institute, Tulcea, Romania

 

1- General information

The common name of this species is “Danube Sturgeon” or “Russian Sturgeon”. Scientifically it was named after the famous naturalist and explorer Johann Anton Güldenstädt of Baltic-German descent who also worked on behalf of Catherine the Great from Russia in the 18th century.

 

2- Occurrence

The Danube Sturgeon occurred in the Black, Azov and Caspian Seas and their large river tributaries. In addition to the sea-migrating form, a freshwater form has been reported from various rivers including the middle part of the Danube River in Slovakia and Hungary.

 

In past centuries this species regularly migrated in the Danube River up to Bratislava in Slovakia (river km 1,869) and rarely even as far as Vienna in Austria (river km 1,925) and Regensburg in Germany (river km 2,381). It was also recorded in some of the larger tributaries such as the Vah, Drava, Sava, Tisza and Morava Rivers.

 

3- Biology

Acipenser gueldenstaedti is one of the largest of the surviving Danube River sturgeon species, reaching documented lengths of more than 2 meters and an age of more than 30 years. Females and males mature at the age of 12 to 16 years and 11 to 13 years, respectively. Depending on size, the female spawner can carry from 30,000 to more than 400,000 eggs.

 

This species lives in the shallow waters on the continental shelf of the Black Sea, mainly in brackish water where high densities of food organisms like crabs, mussels, snails and small bottom dwelling fishes prevail – the main prey items for adults, as well as small crustaceans and insect larvae – the prey favoured by juveniles.

 

4- Spawning migration

The spawning run into the rivers usually begins in early spring, reaches its peak in mid- or late summer and ceases in late autumn. There is also evidence for a dual-peaked migration in certain years with increased numbers of spawners entering the Danube in spring and in fall. The latter overwinter in the river and spawn in the following spring.

 

This species needs hard bottom substrates to spawn in the river. The eggs are released over gravel or stony beds at depths of 4 to 25 m, where there is a strong current and mostly in the main channel of the river. The eggs are sticky and cling to the gravel and rocks, where they develop until the young sturgeons hatch and start their journey downstream to the Black Sea. Some historical spawning sites in Hungary and Slovakia were documented but are no longer used due to the blocking of the spawning migration at the Iron Gate impoundments. Current spawning sites downstream of the Iron Gate dams are unknown.

 

5- Status and conservation

Once quite common in the lower and middle stretches of the Danube River up to Slovakia, this species is now restricted to the Serbian, Bulgarian and Romanian Danube downstream of the Iron Gate dams. Only very few individuals have been recorded recently entering the river for spawning. According to the IUCN Red List (2010) Acipenser gueldenstaedti is critically endangered. Immediate rescue measures are important for the survival of this species in the Danube River.