Starry sturgeon

The starry sturgeon (Huso stellatus),^[5] also known as the stellate sturgeon or sevruga (Drakul, Persian: اوزون برون, and Turkish: Uzun Burun, lit. 'long nosed'), is a species of sturgeon. It is native to the Black, Azov, Caspian and Aegean sea basins, but it has been extirpated from the last and it is predicted that the remaining natural population will follow soon due to overfishing.^[1]

The starry sturgeon is an anadromous species, which migrates up rivers to spawn.^[6]

It is considered critically endangered by the IUCN and international trade in this species (including its caviar) is restricted by CITES.^[1]

Prior to 2025, it was placed in the genus Acipenser, but this placement was found to be paraphyletic, and it is more accurately placed in the genus Huso.^[5][7] Both of which, however, refer to the common name starry sturgeon.^[8]

• A. stellatus
• H. stellatus

The starry sturgeon reaches about 220 cm (7.2 ft) in length and weighs up to 80 kg (180 lb).^[6] It is a slim-bodied fish easily distinguished from other sturgeons by its long, thin and straight snout that makes up roughly 25% of its total length.^[9]

A row of five small barbels lies closer to the mouth than to the tip of the snout. The scales on the lateral line number between thirty and forty and these features distinguish this fish from the Russian sturgeon (H. gueldenstaedtii).^[10] It has many scutes along its top side as an act of protection. It has 9-16 on its dorsal, 26-43 on its lateral, 9-14 residing on the ventral, 40-54 resting on the dorsal fin rays, and 22-35 protecting the anal fin rays.^[9]

Its general colouring is dark greyish-green or brown with a pale underside. The scales on the lateral line are pale.^[10] The maximum reported age for this species is 27 years.^[6]

The starry sturgeon is a harmless species, thereby lacking significant natural protection and pose no threat to predators, that feeds on fish, worms, crustaceans and mollusks.^[6] It lies on the bottom of the seabed during the day and feeds mostly at night.^[10]

This fish is anadromous and moves upriver into shallow waters to spawn during spring and winter.^[10]

Male sturgeons reproduce every 2-3 years after 6-12 years of sexual maturity development, while females follow suite every 3-4 years after 8-14 years of sexual maturity. Both must reproduce under optimal hydrological conditions in their spawn habitat to ensure the highest success rate of egg survival.^[11]

Spawning sturgeon appears at depths up to 5 m (16.4 ft) on the stone ground of riverbeds with a preferred water flow velocity of >1 m/s (2.2 mph). This allows efficient juvenile migration from spawn site to sea in order to distribute throughout the bodies of water.^[12]

During migration, starry sturgeons do not seek or consume food until after the spawning period is complete, in which the species will move out of the spawn site to begin feeding.^[13]

Optimal temperatures for growing juveniles is between 25-26°C (77-78.8°F) to promote the best rate of growth within a spawn site. However, higher temperatures beyond this result in lower chances of survival when the juvenile species transitions into adulthood, increasing environmental vulnerabilities when an individual sturgeon leaves the spawn site.^[14]

The starry sturgeon can be found in coastal, sea, and estuarine environments. They can mainly be residing in the Caspian sea, Black sea, Sea of Asov, and the Aegean Sea.^[11]

However, during spring spawn season, the species is known to migrate to rivers with heavy currents and have a preference for stone-filled river bottoms. If a river is not an optimal spawn habitat, sturgeon have been recorded to reside in flooded river banks with sandy ground.^[11]

The starry sturgeon is an important commercial fish species that serves as food in many cuisines across Europe. It is an essential source of caviar, see Sevruga caviar, that food industries use along with the Beluga sturgeon and the Ossetra sturgeon.^[15] Its meat is packed with vitamins, amino acids, and mineral.^[16] It can be a common ingredient in kababs, and can be cooked in various methods such as pan frying, smoking, and broiling as seen in the Caspian regions, where the meat is a delicacy.^[15]

In aquaculture, many countries around the world have attempted to farm the starry sturgeon, along with other sturgeon species, in hopes of supplying the increasing demand for its meat and caviar. Although, due to natural resource destruction and overfishing, the sustainability of these harvesting facilities become lost.^[16]

With a recorded minimal population doubling time of 4.5 – 14 years, the species' ability to recover from a population loss is difficult to achieve in large quantities.^[15]

The starry sturgeon species is threatened by habitat loss, overfishing, introduction of unfamiliar pathogens, and increased competition from non-native sturgeon species.^{[17][18][19][20]}

The species is believed to have undergone a loss of 95% of its population in three generations. Illegal fishing is a major threat to the survival of this species.^[1]

On the IUCN Red List of Threatened Species, the starry sturgeon was classified under the "Critically Endangered" in the year 2019.^[1]

During migration across the Caspian Sea, the starry sturgeon is vulnerable to illegal trawling, gillnetting, and other fishing practices. This is difficult to regulate, however, due to multiple countries possessing different bodies of the sea, all of which contain different laws and regulations.^[19]

With commercial fishing providing 90% of the world's wild caviar supply, the species has faced increased fishing practices to meet the market demands, as well as habitat degradation from vessels, and introduction of invasive species. These have contributed to the increased depletion of the species' population size in the environment.^[17]

Introducing new sturgeon species, whether through cultivation or accidental release, can spread pathogens to native starry sturgeons, as well as other neighboring species. In addition to this, starry sturgeons can experience genetic deviation from potential hybridization of non-native sturgeons, affecting the natural diversity in the native ecosystem, and also lead to changes in territorial and aggressive behavior due to increased competition for mating, food, and territory. As such, introgressive hybridization can pose a risk of reducing the native species as a tradeoff for alien sturgeon species.^[18]

Overfishing throughout the Caspian Sea has caused the rapid depletion of the species by catching more mature sturgeon that fish hatcheries can replenish using broodstock methods. Reducing stock populations of wild starry sturgeons and resulting in the loss of spawn sites with the combined efforts of overfishing and poaching.^[20]

Conservation efforts of this species require an understanding of the migration routes, preference to specific locations, and a stock's influence on individual sturgeon.^[19]

Hatcheries along Caspian territories and independent countries like Ukraine, Kazakhstan, and Azerbaijan, have been constructed to artificially breed starry sturgeons and other sturgeon species to facilitate the reproduction rate of stock. By promoting the natural life cycle of sturgeons from egg to adulthood, the countries involved have increased the release of juveniles into the Caspian Sea to combat the population decline. Though, the limited source of wild brood stock poses a risk of domestication of wild production and lack of genetic diversity in the species, which leads to vulnerabilities in low adaptive capabilities to the natural environment.^[21]

• World Sturgeon Conservation Society

• Media related to Acipenser stellatus at Wikimedia Commons