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Stellate sturgeon (Acipenser stellatus) is one of the main species of sturgeon, known for its caviar production along with beluga and sturgeon. The stellate sturgeon is also known as the star sturgeon due to the distinctive star-shaped bony plates on its body. This fish species is listed as endangered. Stellate sturgeon does not tolerate low levels of oxygen, so additional oxygenation in the summer months is important for it.
Origin of the species and description
Photo: Sevruga
The common name for this species is “star sturgeon.” The scientific name "stellatus" is a Latin word meaning "covered with stars." This name refers to the star-shaped shape of the bony plates covering the body of this animal.
Video: Sveruga
Sturgeons, to which the stellate sturgeon belongs, are one of the oldest families of bony fish, native to subtropical, temperate and subarctic rivers, lakes and coastlines of Eurasia and North America. They are distinguished by their elongated bodies, lack of scales and rare large size: sturgeons 2 to 3 m long are common, and some species grow up to 5.5 m. Most sturgeon are anadromous bottom feeders, spawning upstream and feeding in river deltas and river mouths Although some are entirely freshwater, very few reach the open ocean beyond coastal areas.
Stellate sturgeon swims in temperate freshwater, brackish and sea waters. It feeds on fish, mollusks, crustaceans and worms. It mainly lives in the basins of the Black and Caspian Seas and the Sea of Azov. The largest population is in the Volga-Caspian region. There are two different spawning cycles for this species. Some fish spawn in winter and some in spring.
Description
The lower lip is interrupted in the middle. The snout of the stellate sturgeon is very long (xiphoid), narrow and flattened, its length is 62-65% of the length of the head. The antennae are without fringes, short, and do not reach the end of the snout and mouth. The mouth is small, slit-shaped when closed, and when capturing food it forms a small “proboscis” curved downwards. The dorsal fin has 40-46 rays, the anal fin 24-29 (in the North Caspian fin there are often 25-27). Caspian fish usually have 24-26 gill rakers. There are 9-16 dorsal bugs, 26-43 lateral bugs, 9-14 abdominal bugs. The sides of the body between the rows of beetles are usually covered with star-shaped plates and small comb-like grains. The pectoral fin spine is weak. Easily forms crosses with sterlet and thorn.
Appearance and features
Photo: What does sturgeon look like?
The general features of sturgeon are as follows:
- the base of the skeleton is not the spine, but a cartilaginous chord;
- the dorsal fin is located far from the head;
- the larvae develop over a long period of time, feeding on substances contained in the yolk sac;
- the anterior ray of the pectoral fin is a spine;
- along the body (on the back, stomach, sides) there are rows of large pointed outgrowths. Between them the animal is covered with small bone tubercles and granules.
Stellate sturgeon is a valuable commercial fish. It has two forms - winter and spring. It differs from all other fish of the sturgeon family in appearance. A distinctive feature of the stellate sturgeon is its unusually long nose, shaped like a dagger. The forehead of this fish is rather prominent, the narrow and smooth antennae do not reach the mouth, and the lower lip is very poorly developed.
The body of the stellate sturgeon, like the nose, is elongated, covered on each side and on the back with scutes, closely spaced to each other. The body of this fish is red-brown in color with a slight bluish-black tinge on the back and sides with a white stripe on the belly.
Stellate sturgeon is a rather slender fish, it is easy to distinguish by its muzzle, which is long, thin and fairly straight. The side shields are small. These features distinguish the stellate sturgeon from the sturgeon that has been discovered in Finnish waters in recent years. The back of the sturgeon is dark grayish-green or brown, the belly is pale. The lateral scutes are pale. Stellate sturgeon is somewhat smaller in size than most sturgeon. Its average weight is about 7-10 kg, but some individuals reach a length of more than 2 m and a weight of 80 kg.
Maturation and nutrition
The bulk of the Volga sturgeon matures: males - at the age of 9-12 years, females - at the age of 11-15 years. Males of the Kursk stellate sturgeon mature at the age of 11-13 years, females at the age of 14-17 years. Males in the Urals mature at 7-8 years, females at 13-14 years; in the Don and Kuban, males - at 5-8 years, females - at 8-12 years; in Sefidrud, males - at 13-14 years old, females - at 16-17 years old. Life expectancy is up to 30 years. Stellate sturgeon feeds on invertebrates (crustaceans, worms) and fish (gobies, herring and sprat). The average fishing weight of Volga sturgeon is 8-9 kg, Kurin - 7-8 kg, Ural - 5-10 kg, Kuban - 6-8 kg, Don - about 7-8 kg. The highest weight was recorded for the Danube - 80 kg, Kura - 70 kg, Don - 67 kg. There are known crosses between stellate sturgeon and sterlet (“stellate thorn” - in the Volga, Danube, Don), with thorn (“stellate thorn” - in the Urals, Kura). It was possible to obtain viable hybrids: sterlet X stellate sturgeon and stellate sturgeon X sterlet. Stellate sturgeon takes first place in the sturgeon fishery.
Where does the sturgeon live?
Photo: Sevruga in Russia
Stellate sturgeon lives in the Caspian, Azov, Black and Aegean seas, from where it enters tributaries, including the Danube. This species is rarely found in the Middle and Upper Danube, only occasionally the fish migrate upstream to Komárno, Bratislava, Austria or even Germany. This species is found in small quantities in the Aegean and Adriatic Seas, as well as in the Aral Sea, where it was introduced from the Caspian Sea in 1933.
During spawning migrations, the stellate sturgeon also found its way into tributaries of the Lower Danube River, such as the Prut, Siret, Olt and Zhiul rivers. In the Middle Danube, it migrated to the Tisa River (up to Tokaj) and to the lower reaches of its tributaries, the Maros and Körös Rivers, as well as to the mouth of the Zagywa River, the lower reaches of the Drava and Sava Rivers and the mouth of the Morava River.
As a result of regulation and damming of rivers, the range of stellate sturgeon in the catchment areas of the Caspian, Azov and Black Seas has been significantly reduced. The area of spawning grounds has decreased significantly, and migration routes and timing have changed. Currently, most individuals in the Danube River migrate only as far as the Iron Gate dams.
Stellate sturgeon is usually found in shallow waters of the sea coast and in flat areas of rivers. Small benthic animals are the main food source for adults, and plankton play an important role in feeding during the early larval stages.
Now you know where the stellate sturgeon lives. Let's find out what this fish eats.
Stellate sturgeon lifestyle
Sevruga is a migratory fish. In the sea and rivers it regularly rises to the upper layers at night to feed. Spawning grounds in rivers are located below the spawning grounds of other sturgeon. Spawning migration sometimes lasts more than a year. In most rivers there are 2 movements: spring and autumn. The stellate sturgeon of the autumn season winters in the lower reaches on pits and spawns in the spring and early summer of the next year; The stellate sturgeon, which comes in the spring, breeds in the same summer. It spawns in areas of coastal flood meadows flooded with hollow waters or in the central part of the river at a depth of 9-13 m.
What does the sturgeon eat?
Photo: Sevruga in the sea
The seven most common species of sturgeon, including the stellate sturgeon, skip dust in lakes and rivers, feeding mainly on crayfish, shrimp, snails, plants, aquatic insects, larvae, mud worms and mollusks.
Interesting fact: Stellate sturgeon stops eating as soon as it begins to migrate. After spawning, she quickly returns to the sea, where she begins to feed again.
Stellate sturgeon are excellent bottom feeders because they have very sensitive antennae on the underside of their snouts to detect bottom animals and their long, bulbous mouth to suck out prey. The gastrointestinal tract of the sturgeon is also very unique because the walls of their pyloric stomach are hypertrophied into a stomach-like organ, the intestines of adults have a functional ciliated epithelium, and their hindguts develop into spiral valves.
Domestic stellate sturgeon, kept in private ponds, need vitamins, oil, minerals and a minimum of 40% protein (most from fishmeal). Among the fat-soluble vitamins, they require vitamins A, D, E and K. Their water-soluble vitamins include B1 (thiamine), B2 (riboflavin), B6, B5, B3 (niacin), B12, H, C (ascorbic acid) and folic acid.
Features of character and lifestyle
Photo: Sevruga fish
Although the stellate sturgeon has been the focus of attention in aquaculture because it is a valuable source of caviar, there is a serious lack of knowledge about the biology and behavior of this species in the wild (home range, aggregation, aggression, for example), as well as many aspects of agriculture (aggression, environmental enrichment). environment, stress and slaughter). Lack of knowledge not only makes it seriously difficult to assess the state of her well-being, but also hinders almost any prospect of improving it.
Different species of sturgeon have high plasticity in relation to spawning behavior. Multiple spawning runs occur when one species has distinctly separate groups spawning in the same river system, which we call "double spawning." Spawning groups are described as spring and himal spawning races.
Distinct spawning groups have been described for several sturgeon species around the world. Double spawning occurs in many Eurasian sturgeon species. In the Black and Caspian Seas there are several species with spring and himal races: beluga, Russian sturgeon, thorn, stellate sturgeon, sterlet. The spring group enters the river during the spring with almost mature gonads and spawns shortly after entering the river. The hemal group enters the river at the same time or immediately after the spring group, but with immature oocytes.
Social structure and reproduction
Photo: Sevruga from the Red Book
This species spawns on the banks of rivers flooded by spring floods and over the rocky bottom of the riverbed during fast currents. Eggs are laid on beds of scattered stones, pebbles and gravel mixed with shell fragments and coarse sand. Optimal spawning conditions include high flow rates and a clean gravel bottom. Reduced flow rates after spawning and egg development can lead to increased embryo losses. In the Danube River, spawning occurs from May to June at temperatures ranging from 17 to 23° C. Not much is known about the spawning habits of this species.
After hatching, stellate sturgeon larvae live not only in the lower and middle layers of river water, but also on the surface. They drift downstream, and during subsequent development their ability to actively move increases. The distribution of juveniles along the Danube riverbed is influenced by food supplies, current and turbidity. They migrate downstream at a depth of 4 to 6 m. Life expectancy in the river lasts from May to October, and active feeding begins when the larvae reach 18-20 mm.
Interesting fact: Stellate sturgeon can reach more than 2 meters in length and a maximum age of 35 years. Males and females take up to 6 and 10 years, respectively, to mature. Females can lay between 70,000 and 430,000 eggs, depending on their size.
Like other sturgeon, the stellate sturgeon enters the Danube River to spawn almost all year, but there are two peak periods. This process begins in March at water temperatures from 8 to 11° C, reaches its maximum intensity in April and continues until May. The second, more intense migration begins in August and continues until October. This species prefers warmer habitats than other Danube sturgeons, and its spawning flows occur at water temperatures higher than those prevailing during the migrations of other species.
Natural enemies of sturgeon
Photo: Sevruga
The enemies of sturgeon are people. Their late sexual maturity (6-10 years) makes them more vulnerable to overfishing. It is estimated that their numbers in major basins have declined by 70% over the last century. During the 1990s, the total catch was increased dramatically due to unprecedented illegal fishing. Poaching in the Volga-Caspian basin alone is estimated to be 10-12 times higher than acceptable limits.
River flow regulation and overfishing are the main reasons for the decline in sturgeon numbers in the 20th century. During the 1990s, the total catch was increased dramatically due to unprecedented illegal fishing. In the Volga-Caspian basin alone, poaching activity is estimated at 10-12 times more than legal catch. The same situation is happening on the Amur River. Overfishing and poaching have led to a significant reduction in the total legal catch worldwide and especially in the main sturgeon basin, the Caspian Sea.
Caviar is the unfertilized eggs of sturgeon. For many gourmets, caviar, called “black pearls,” is a food delicacy. The three main commercial sturgeon species produce specialty caviar: beluga, osetra (Russian sturgeon) and stellate sturgeon (star sturgeon). The color and size of the caviar depends on the type and stage of maturity of the caviar.
Today, Iran and Russia are the main exporters of caviar, about 80% of which comes from three species of sturgeon in the Caspian Sea: Russian sturgeon (20% of the market), stellate sturgeon (28%) and Persian sturgeon (29%). Stellar sturgeon problems are also caused by water pollution, dams, destruction and fragmentation of natural watercourses and habitats, which affects migration routes and feeding and breeding areas.
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September 26, 2021, Sunday
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Population and species status
Photo: Sevruga fish
Stellate sturgeon has always been a rare inhabitant in the Middle and Upper Danube and is currently extirpated from the upper Danube and the Hungarian-Slovak section of the Middle Danube, since only a few people manage to pass through the locks on the Iron Gate dams. The last known specimen from the Slovak section was taken from Komárno on 20 February 1926, and the last from the Hungarian section was recorded from Mohács in 1965.
According to the Red Book, the stellate sturgeon is endangered as a result of overfishing, poaching, water pollution, and the damming and destruction of natural watercourses and habitats. However, according to modern observations on the Danube, it is close to extinction. The current status of the population, which has suffered greatly from past overfishing, and the exact location of the spawning grounds are unknown. More research is needed to effectively implement conservation measures for this species.
Interesting fact: 55,000 sturgeon were found dead in the Sea of Azov in 1990 as a result of pollution. The 87% decline in global commercial catch reflects declining populations of the species.
Wild sturgeon (common sturgeon, Atlantic sturgeon, Baltic sturgeon, European sea sturgeon) have not been caught off the coast of Finland since the 1930s. The most likely species to end up in Finnish sea waters are the stellate sturgeon. They may also disappear as stored specimens die off. Sturgeon live a long time, so this process will likely take some time.
