Stellate sturgeon

Stellate sturgeon (Acipenser stellatus) is one of the main species of sturgeon, known for caviar production along with sturgeon and sturgeon. The stellate sturgeon is also known as the star sturgeon because of the characteristic star-shaped bone plates on its body. This fish species is listed as critically endangered. The stellate sturgeon does not tolerate low levels of oxygen, so additional oxygenation during the summer months is essential for it.

Origin of the species and description

Photo: Sevruga

Photo: Sevruga

Common name of this species &#8212 ; “star sturgeon”. Scientific name “stellatus” — Latin word meaning “covered with stars”. This name refers to the star-shaped bony plates that cover the body of this animal.

Video: Sveryuga

Sturgeons, to which 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: sturgeon 2 to 3 m long are common, and some species grow up to 5.5 m. river mouths. Although some are completely freshwater, very few go out into the open ocean outside of coastal areas.

The stellate sturgeon swims in temperate freshwater, brackish and marine 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.

Appearance and Features

Photo: What the sturgeon looks like

Photo: What stellate sturgeon looks like

The general features of sturgeon are as follows:

  • the base of the skeleton — not a spine, but a cartilaginous chord;
  • the dorsal fin is far from the head;
  • larvae develop for a long time, feeding on substances contained in the yolk sac;
  • the anterior ray of the pectoral fin is a spike;
  • along the body (on the back, abdomen, sides) there are rows of large pointed outgrowths. Between them, the animal is covered with small bony tubercles, granules.

Stellate sturgeon is a valuable commercial fish. It has two forms — winter and spring. From all other fish of the sturgeon family, it differs in appearance. A distinctive feature of the stellate sturgeon is an unusually long nose, shaped like a dagger. The forehead of this fish is quite protruding, narrow and smooth antennae do not reach the mouth, the lower lip is very poorly developed.

The body of the stellate sturgeon, like the nose, is elongated, on each side and on the back it is covered with shields, densely located to each other. The body of this fish has a red-brown color with a slight bluish-black tint on the back and sides with a white stripe on the belly.

The stellate sturgeon is a fairly slender fish, easily recognizable by its snout, which is long, thin and fairly straight. 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 stellate sturgeon is dark grayish-green or brown, the belly is pale. Lateral shields are pale. The stellate sturgeon is somewhat inferior in size to most sturgeons. 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.

Where does the stellate sturgeon live?

Photo: Stellate sturgeon in Russia

Photo: Stellate sturgeon in Russia

The 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 does the fish migrate upstream to Komarno, Bratislava, Austria or even Germany. In small quantities, this species is found in the Aegean and Adriatic Seas, as well as in the Aral Sea, where it was brought from the Caspian Sea in 1933.

During spawning migrations, stellate sturgeon also entered the tributaries of the Lower Danube River, such as the Prut, Siret, Olt and Zhiul rivers. In the Middle Danube, it migrated to the Tisza 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 Zagyva River, the lower reaches of the Drava and Sava rivers and the mouth of the Morava River.

As a result of river regulation and damming, the range of stellate sturgeon in the catchment areas of the Caspian, Azov and Black Seas has significantly decreased. The area of ​​spawning grounds has significantly decreased, and the routes and timing of migration have changed. Currently, most individuals in the Danube River migrate only to the dams of the Iron Gates.

Stellate sturgeon is usually found in the shallow waters of the sea coast and in the flat areas of rivers. Small benthic animals are the main source of food for adults, and plankton plays an important role in feeding in early larval stages.

Now you know where the stellate sturgeon lives. Let's find out what this fish eats.

What does the stellate sturgeon eat?

Photo: Stellate sturgeon in the sea

Photo: Stellate sturgeon in the sea

The seven most common sturgeon species, including stellate sturgeon, pass dust in lakes and rivers, feeding mainly on crayfish, shrimps, snails, plants, aquatic insects, larvae, mud worms and molluscs.

Interesting fact: Sevruga stops eating as soon as it starts migrating. 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 barbels on the underside of their snouts to detect bottom-dwelling animals and their long and bulging mouth to suck out prey. The gastrointestinal tract of the stellate sturgeon is also very unique because the walls of their pyloric stomach are hypertrophied into a stomach-like organ, the intestines of adults have functional ciliated epithelium, and their hindgut develops into helical valves.

Domestic stellate sturgeon kept in private ponds need vitamins, oil, minerals and a minimum of 40% protein (most fishmeal). Among the fat-soluble vitamins, they need 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.

Character and lifestyle features

Photo: Sturgeon fish

Photo: Sturgeon fish

Although stellate sturgeon is the focus of aquaculture as 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 very difficult to assess the state of her well-being, but also makes almost any prospect of improvement difficult.

Different species of sturgeon have high plasticity in terms of spawning behavior. Multiple spawning runs occur when one species has distinctly separate groups spawning in the same river system, which we refer to as “double spawning”. Spawning groups are described as spring and himal spawning races.

Separate 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, spike, stellate sturgeon, sterlet. The spring group enters the river during the spring with nearly 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: Stellate sturgeon from the Red Book

Photo: Stellate sturgeon from the Red Book

This species spawns on the banks of rivers flooded by spring floods and above the rocky bottom of the channel with 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 clean gravel bottoms. A decrease in the flow rate after spawning and egg development can lead to an increase in embryo loss. In the Danube River, spawning occurs from May to June at temperatures between 17 and 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 is influenced by food supplies, current and turbidity. They migrate downstream at a depth of 4 to 6 m. The lifespan 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 over 2 meters in length and a maximum age of 35 years. Males and females take up to 6 and 10 years to mature, respectively. Females can lay between 70,000 and 430,000 eggs, depending on their size.

Like other sturgeons, the stellate sturgeon enters the Danube River to spawn most of the year, but there are two peak periods. This process begins in March at a water temperature of 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 streams occur at water temperatures higher than those prevailing during migrations of other species.

Natural enemies of stellate sturgeon

Photo: Sevruga

Photo: Sevruga

The enemies of the stellate sturgeon are people. Late sexual maturity (6-10 years) makes them more vulnerable to overfishing. It is estimated that their numbers in large basins have declined by 70% over the last century. During the 1990s, the total catch was drastically increased by unprecedented illegal fishing. Poaching in the Volga-Caspian basin alone is estimated to be 10 to 12 times the legal limit.

Regulation of river flow and overfishing are the main reasons for the decline in the number of stellate sturgeons in the 20th century. During the 1990s, the total catch was drastically increased by unprecedented illegal fishing. Only in the Volga-Caspian basin, poaching activity is estimated at 10-12 times more than the legal catch. The same situation occurs on the Amur River. Overfishing and poaching have led to a significant reduction in the total legal catch in the world and especially in the main stellate sturgeon basin — Caspian Sea.

Caviar — These are unfertilized sturgeon eggs. For many gourmets, caviar, called “black pearls”, is a food delicacy. Three main commercial sturgeon species produce special caviar: beluga, sturgeon (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 is harvested by three types of sturgeon in the Caspian Sea: Russian sturgeon (20% of the market), stellate sturgeon (28%) and Persian sturgeon (29%). Also, stellate sturgeon problems are caused by water pollution, dams, destruction and fragmentation of natural watercourses and habitats, which affects migration routes and places for feeding and breeding.

Population and species status

Photo: Stellate sturgeon fish

Photo: Stellate sturgeon fish

The stellate sturgeon has always been a rare inhabitant of the Middle and Upper Danube and is now extirpated from the upper Danube and the Hungarian-Slovak section of the Middle Danube, as only a few people manage to get through the locks on the dams of the Iron Gates. The last known specimen from the Slovak section was taken at Komárno on February 20, 1926, and the last from the Hungarian section was recorded at Mohács in 1965.

According to the Red Book, stellate sturgeon is endangered as a result of overfishing, poaching, water pollution, damming and destruction of natural streams and habitats. However, according to modern observations on the Danube, it is close to extinction. The current status of the population, which has been severely affected by 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 stellate sturgeons were found dead in the Sea of ​​Azov in 1990 as a result of pollution. The 87% decline in global commercial catches reflects the decline in populations of the species.

Wild sturgeon (common sturgeon, Atlantic sturgeon, Baltic sturgeon, European sea sturgeon) has not been caught off the coast of Finland since the 1930s -s. The stellate sturgeon are the most likely species to end up in Finnish marine waters. They may also disappear as stocked specimens die off. Sturgeons live a long time, so this process will probably take some time.

Stellate Sturgeon Protection

Photo: Stellate sturgeon from the Red Book

Photo: Stellate sturgeon from the Red Book

Almost all sturgeon species are classified as endangered. Their highly prized meat and eggs (more commonly known as caviar) have led to massive overfishing and a decline in the sturgeon population. River development and pollution have also contributed to population decline. The European sea sturgeon, once endemic in Germany, became extinct about 100 years ago. This species is expected to return to the rivers of Germany through reintroduction projects.

The global strategy to combat the extinction of sturgeon outlines the main directions of work for the conservation of sturgeons for the next 5 years.

The strategy is focused on :

  • fight against overexploitation;
  • restoration of life cycle habitat;
  • conservation of the sturgeon stock;
  • communication.

WWF is engaged in conservation activities on the ground in different regions and countries. Country-specific actions include actions in Austria (information in German), Bulgaria (Bulgarian), the Netherlands (Dutch), Romania (Romanian), Russia and the Amur River (Russian) and Ukraine (Ukrainian).

In addition, WWF is active in:

  • the Danube River Basin with a special project to combat the overexploitation of sturgeon in the Danube;
  • restoring more natural flows of the Saint John River in Canada.

Stellate sturgeon — one of the most valuable species of sturgeon in the world. These archaic aquatic giants face numerous threats to their survival. Despite surviving on Earth for millions of years, stellate sturgeons are currently vulnerable to overfishing and interference with their natural habitat. The stellate sturgeon is endangered.

Rate article
Add a comment