Species: Russian sturgeon (Acipenser gueldenstaedtii)
Status: Critically Endangered (CR)
Interesting Fact: The Russian sturgeon can reach lengths of nearly two and a half metres.
More information: The Russian sturgeon belongs to an ancient and unique group of fish, relics from the time of the dinosaurs. This prehistoric giant was formerly found in the Black, Azov, and Caspian Seas in Eastern Europe and the Middle East, as well as the deep sections of fast-flowing rivers, such as the Volga, Danube, and Ural Rivers. Populations of this species are now mostly found in the lower reaches of these river systems and along coastlines.
The male Russian sturgeon does not reproduce until it is between 8 and 13 years old and only do so every 2 or 3 years, while the female does not reach sexual maturity until it is 10 to 16 years old and then only reproduces every 4 to 6 years. There are two distinct forms of this fish species, the anadromous type which migrates up rivers from the sea to spawn and the freshwater form which remains in its freshwater habitat to spawn, although this form is now thought to be extinct. For the anadromous type, there are two separate migrations, one in spring when spawning occurs in the lower levels of the river and one in autumn when individuals migrate into freshwater where they spend the winter before spawning upstream the following spring.
Vast areas of the Russian sturgeon’s spawning grounds have been lost due to damming and exploitation. Dam construction is highly detrimental to this and other migratory fish species, as the usual migration routes to its spawning grounds are blocked, meaning that individuals either do not reproduce, or spawn in unsafe areas. Pollution in the Caspian and Black Sea basins is causing hormonal imbalances in this species and subsequently a greater number of hermaphroditic, infertile individuals are found in these areas.
The Russian sturgeon was once very important commercially, and its caviar was one of the most sought after of any species. Illegal fishing still continues, despite legal catch quotas being in place, with the illegal catch thought to far surpass the legally set limits. The Russian sturgeon is unprotected in many areas throughout its range and the absence of a strict monitoring system makes the control of fishing very difficult. Despite restocking efforts, the creation of artificial spawning grounds, and the introduction of fish lifts to help individuals to get around dams, the population is still in decline and over the last 15 years, global catches have dropped by 98 percent. As a slowly maturing species, it does not have the ability to recover from overexploitation, especially without complete cessation of fishing.
Find out more about sturgeon conservation.
Hannah Mulvany, ARKive Content and Outreach Officer