Sterlet

Origin of the species and description

Photo: Sterlet

The history of the species dates back to the end of the Silurian period - about 395 million years ago. It was during this period that an important evolutionary change occurred in prehistoric fish-like fish: the transformation of the anterior gill arches in the jaws. First, the gill arch, which has a ring shape, acquired an articular joint that helps it fold into a double half ring. The result was some semblance of a grasping claw. The next stage is connecting the skull with the upper half-ring. The other of them (the future lower jaw) retained mobility.

As a result of the changes that occurred with fish, they turned into real predators, their diet became more varied. While the ancestors of sterlets and other sturgeons only filtered plankton. The appearance of sterlets, the one with which they have survived to this day, was formed 90-145 million years ago. We can say that these fish are contemporaries of dinosaurs. Only, unlike prehistoric reptiles, they safely survived a number of global catastrophes and reached the present day practically unchanged.

This indicates the ecological plasticity of fish, the ability to adapt to environmental conditions and use the resources allocated by nature to the maximum. The heyday of sterlet and other sturgeon dates back to the Mesozoic era. Then some of them were replaced by bony fish. However, unlike armored species, sturgeons survived quite successfully.

Beluga

Beluga is slightly different in appearance from sterlet and sturgeon. It's all about the massive thick body and blunt snout. It’s not for nothing that its Latin name translates as “pig.” At the same time, it reaches very impressive sizes. In fishing, there have been known cases of catching belugas weighing more than 1000 kg. At the moment, the average weight ranges from 200 to 300 kilograms. In addition, these fish are also long-lived: the age of some specimens exceeds 100 years. However, the average life expectancy is 45-50 years.

In addition to its massive body, the beluga is distinguished by a truly large mouth, which the fish needs to catch food. The lips have a width comparable to the width of the head. The antennae are just as big: they easily reach the mouth.

It can have winter and spring forms. It depends on where the fish spawn and live. Since young animals prefer to feed on crustaceans, they stay closer to places where they accumulate – river mouths. There the shells are not so hard and quite small.

Beluga is a predatory fish. It feeds on bream, roach and carp. He does not disdain his fry, even relatives in appearance - other sturgeon.

Beluga begins to reproduce very late: females - at 18 years, males - at 14-15. The main river for spawning is the Don. However, the decline in numbers is greatly influenced by the construction of dams that regulate river floods.

Appearance and features

Photo: Sterlet fish

The sterlet belongs to the subclass of cartilaginous fish. The appearance of the scales resembles bone plates. The spindle-shaped elongated body is completely covered with them. The characteristic feature of sturgeon fish is the cartilaginous notochord, which forms the basis of the skeleton. Even adult fish have no vertebrae. The skeleton and skull of sterlets are cartilaginous; there are 5 lines of bone spines on the body.

The mouth is retractable, fleshy, teeth are missing. Below the spine is the swim bladder, connected to the esophagus. Sterlets and other sturgeons have squirts - openings that extend from the gill cavities to the covers. The great white shark has something similar. The number of main gills is 4. Gill rays are absent.

The sterlet has an elongated body and a relatively large triangular head. The snout is elongated, conical in shape, the lower lip is forked. These are the distinctive features of fish. At the bottom of the snout there are fringe whiskers, which are also found in other sturgeon species. There are 2 varieties of sterlets: sharp-snouted (classic version) and blunt-snouted, with a slightly rounded nose. As a rule, blunt-snouted individuals include individuals that are not capable of reproducing, as well as domesticated ones that are bred artificially. The eyes of sterlets are small and protruding.

On the surface of the sterlet's head there are bony scutes fused together. The body is covered with ganoid (containing an enamel-like substance) scales with comb-like projections that resemble grains in appearance. A feature that distinguishes sterlets from most other fish is the dorsal fin shifted towards the tail. The shape of the tail is typical for sturgeon: the upper blade is longer than the lower one. As a rule, sterlets are gray-brown in color, sometimes with light yellow areas. The lower part is lighter than the back; in some individuals the abdomen is almost white.

Of all sturgeon fish, the sterlet is the smallest. The length of adult individuals is rarely more than 1.2-1.3 m. Most cartilaginous animals are even smaller - 0.3-0.4 m. Sterlets have no sexual dimorphism. Males and females are completely identical in color and size. The type of scales they have is also practically the same.

Bone scutes instead of scales

There are no scales, but the body is protected by thin bone shields. They protect the fish from water pressure, injuries and facilitate movement at different depths. Shields are also good against more predatory creatures.

Externally, this armor looks smooth. The fish swims gracefully and quickly, hunting for prey. The shields do not interfere with pirouettes both in the water column and near the bottom.

Moreover, males and females are identical in appearance and size.

Where does the sterlet live?

Photo: What a sterlet looks like

The habitat of sterlets is rivers that flow into the seas: the Black, Caspian and Azov. This fish is also found in the Northern Dvina. From Siberian rivers - in the Ob and Yenisei. The range of sterlet also extends to rivers located in the basin of lakes: Onega and Ladoga. These fish were settled in the Oka, Nemunas (Neman) and some reservoirs. Find out more about the living conditions in the largest bodies of water.

Northern and Western Dvina - sterlets are acclimatized artificially to preserve the species.
Ob. The most numerous populations were recorded near the mouth of the Barnaulka River.
Yenisei. Sterlet is found, as a rule, lower from the mouth of the Angara, as well as in the tributaries of the river.
Nemunas (Neman), Pechora, Oka, Amur - the fish were brought artificially.
Don, Ural - sterlets are rare, literally single specimens.
Sura. Since the middle of the 20th century, the previously large population has become very thin.
Kama. The sterlet population has increased significantly due to a reduction in deforestation and the fact that the water in the river has become significantly cleaner.
Kuban. It is considered the southernmost point of the sterlet's range. The number of sterlets is small, but is gradually increasing.
Irtysh. The most numerous flocks are found in the middle reaches of the river.

Sterlet lives only in clean reservoirs; it prefers soil covered with sand or pebbles. Females stay closer to the bottom of the reservoir, while males are more active and spend most of their time in the water column.

Habitat

It’s not for nothing that sterlet is called a noble fish: it is found only in clean water. The bottom of the reservoir should have sandy or pebbly soil. Where is the sterlet found?

The fish is found at the confluence of large rivers into the Caspian, Black, Barents, Azov and White seas, as well as in the rivers: Volga, Kama, Yenisei, Amur, in Lake Ladoga and Onega.

For a comfortable life, fish need clean, fast-flowing water well enriched with oxygen.
When artificially reared, sterlet is specially maintained at the required water temperature and enriched with oxygen.
Sterlet lives in flocks, with up to one hundred individuals of approximately the same age predominantly gathered in one flock.

During the day, the fish is at the bottom, and at night it rises closer to the shore, in shallow water, to get food for itself. The fish feed from spring to late autumn, until ice is established on the reservoirs. In winter, the fish sink into pits, where in a state of suspended animation they wait out the winter in flocks.

What does a sterlet eat?

Photo: Sterlet in the wild

The sterlet is a predator. The basis of its diet consists of small invertebrates. Mainly, it feeds on bottom animals: small crustaceans, soft-bodied organisms, worms, insect larvae. They feast on sterlet and the caviar of other fish. Adult large individuals feed on small fish, avoiding large prey.

Since females stay near the bottom, and males mainly swim in the water column, their diet is somewhat different. The best time to hunt sterlets is in the dark. The diet of young individuals and fry is microorganisms and plankton. As the fish grows, its “menu” becomes more varied.

Price

In ancient times in Rus', sterlet was extremely expensive. And ordinary people did not have the opportunity to buy such a product. But the royal feasts were not complete without fish soup and aspic made from such fish. Sterlet was delivered to the palace kitchens alive, and transported from afar in cages or oak troughs, where a moist environment was maintained in a special way.

The sterlet catch in our time is constantly declining and is therefore critically small. In view of this, the “royal” fish simply could not turn into one that was especially accessible to the modern consumer. You can buy it in fish and chain stores, markets and restaurants.

The price of sterlet is about 400 rubles per kilogram. And this is only frozen. Live ones cost the buyer more. The caviar of this fish is also valued, and not everyone can afford it. After all, the average buyer is not able to pay 4 thousand rubles for a hundred-gram jar. And this is approximately how much the caviar of this fish costs.

Features of character and lifestyle

Photo: Sterlet

Sterlet is a predator that settles only in clean rivers. Sometimes sterlets swim into the sea, but at the same time stay close to the river mouth. In summer, sterlets stay in the shallows; young animals enter small channels or bays near the mouth. With the onset of autumn cold weather, the fish go deeper, looking for so-called holes. She uses them for the winter. During the cold season, sterlets are inactive, do not eat anything, and do not hunt. After the river opens up, the fish leave deep-sea areas and rush to the upper reaches of the river to spawn.

Sterlets, like all sturgeons, are long-lived among fish. Their life expectancy reaches 30 years. However, it cannot be called a champion of longevity among sturgeons. Lake sturgeon live more than 80 years.

Habitat

Sturgeon fish are predominantly migratory, which means that they live in the sea, but spawn in rivers. Moreover, they prefer the cool waters of northern and middle latitudes: their dense genoid scales are able to withstand low temperatures. The name of sturgeons leading a migratory lifestyle: two types of sturgeon, Russian and Atlantic, beluga, stellate sturgeon, thorn. Only the sterlet does not go to the sea to spawn; it leads a sedentary life in clean rivers with a fairly strong current.

The distribution area is the seas of the northern hemisphere and the rivers flowing into them. These are, first of all, the Black and Caspian, White and Azov seas. Most often, the types of sturgeon fish listed above can be found in the Siberian rivers: Ob, Lena, Yenisei. It should be said right away that this species is on the verge of complete extinction.

They lead a predominantly bottom-dwelling lifestyle, feeding on small fish, invertebrates (mollusks or worms), and do not disdain insects. The Beluga sturgeon is the only predator that feeds not on bottom organisms, but exclusively on fish.

There is another interesting pattern in the diet of this type of fish: they distribute the food base of the reservoir among themselves: for example, the Russian sturgeon prefers mollusks, the sturgeon prefers worms and various crustaceans, and the sterlet prefers invertebrates.

Social structure and reproduction

Photo: Sterlet fish

Most sturgeon are solitary fish. In this regard, sterlet is an exception to the rule. Their peculiarity is that the fish gather in large schools. She even spends the winter not alone, but with numerous brothers. The number of sterlets waiting out the cold in bottom pits is measured in the hundreds. They are pressed so tightly together that they can hardly move their fins and gills.

Males are considered sexually mature at 4-5 years of age. Maturation in females occurs at 7-8 years. 1-2 years after spawning, the female is again ready to reproduce. This is the period necessary for the fish's body to recover from the grueling process of spawning. The breeding season for sterlets occurs in late spring or early summer, most often from mid to late May, when the river water temperature is 7-20 degrees. The best temperature for spawning ranges from 10 to 15 degrees. The spawning period may be earlier or later, depending on the water temperature and its level.

Volga sterlets do not spawn at the same time. Spawning in individuals that settle in the upper reaches of the river begins somewhat earlier. The reason is that the river floods in these places earlier. Fish spawn in clean areas with fast currents and a pebble bottom. The number of eggs laid at one time by a female sterlet exceeds 16 thousand. The eggs are oblong in shape, dark in color. They are covered with an adhesive substance with which they are attached to the stones. After a few days the fry hatch. The yolk sac in young animals disappears around the tenth day. By this time, young individuals reach a length of 15 mm. The fertility of an individual depends on its age. The younger the sterlet, the fewer eggs it lays. Fish over 15 years of age lay about 60 thousand eggs.

The appearance of fry differs from adults. The head is covered with small spines. The mouth is small, transverse. The color is darker than that of adult fish. The tail has a particularly dark shade. Young sterlets grow in the same place where they hatched. Only in autumn do the 11-25 cm young animals rush to the mouth of the river.

An interesting feature: sterlet can interbreed with other sturgeon fish: beluga (hybrid - bester), stellate sturgeon or Russian sturgeon. Besters grow quickly and gain weight. At the same time, sexual maturation of besters, like sterlets, occurs quickly, which makes these fish profitable for breeding in captivity.

Description of sterlet

The exterior of the fish is distinguished by a triangular body with a thin stalk and a sickle-shaped caudal fin with an elongated upper ray. Other features of the appearance of sterlet include:

small cone-shaped head;
elongated narrow nose;
small lower mouth with bifid lip;
small bulging eyes;
fringed antennae;
lack of scales;
5 longitudinal rows of bone scutes (bugs);
gray dorsal fin moved far back;
light yellowish-white abdomen;
ash brown or dark brown color of the ridge.

To distinguish a sterlet from a sturgeon or other members of the family, it is enough to pay attention to the number and arrangement of bony scutes. Acipenser ruthenus is characterized by their tight closure on the back (13-17 pieces). The abdominal 13-15 plates, on the contrary, leave clearly visible gaps between each other. In the lateral line there are many small diamond-shaped bugs adjacent to each other (60-70 pieces), which also make it easy to identify the species among its relatives.

There is a not entirely correct opinion that a sterlet can be distinguished by its elongated, pointed nose. This statement only works on wild and spawn-bearing fish. Cultivated and fattened barren (incapable of reproducing) specimens may also have a shorter snout, like a sturgeon.

Size and sexual maturity

Despite the high-profile title of the king fish, the sterlet is in fact the smallest representative of the family. The standard weight of adult individuals varies between 1-2 kg with a height of 50-60 cm. Much less often, trophy specimens weighing 4-8 kg are found. The largest weight of a sterlet is 15-16 kg with a body length of 120-125 cm. But there is information about particularly large one and a half meter individuals weighing 20 kilograms or more, caught in the Siberian wilderness on the banks of the Irtysh overgrown with taiga.

To learn more:

Is a bream a small bream or not?

The relatively small species size determines the accelerated biological cycle of the sterlet (up to 30 years), which becomes sexually mature already in the third to eighth year of life. At the same time, the larger sturgeon, which lives up to 60-70 years, acquires the ability to reproduce only at the age of 8-20 years.

Natural enemies of sterlet

Photo: What a sterlet looks like

Since the sterlet prefers to stay closer to the bottom of the reservoir, it does not have many enemies. And even those threaten not adults, but fry and eggs. For example, beluga and catfish are not averse to eating sterlet caviar. More effective predators that massively destroy fry and teenage sterlets are pike perch, burbot and pike.

In unfavorable living conditions, fish often get sick.

The most common diseases:

gill necrosis;
gas bubble disease;
saprolegniosis;
myopathy.

Sterlet spawning

Sexual maturity in males occurs after 4-5 years of life, and in females at 6-7 years. Sterlet spawning usually begins in April, when the water warms up to +9-10 C. In the northern regions, reproduction does not start until May. Males are the first to rush upstream, choosing areas in the beds of wide rivers or in the backwaters of the spring flood. Females join when the water warms up to +12-13 C. Spawning takes place at a depth of 8-15 meters, in areas with a rocky and uneven bottom.

The eggs stick tightly to stones, gravel or underwater cartilage and are not washed away even by strong currents. The dark gray or black eggs have a sticky structure and are usually 2-3 mm in diameter and weigh 7-8 mg. The larva develops in 5-9 days, and at first the sterlet feeds on the granules of its yolk sac. After 2 weeks, the natural sac is depleted, and the sterlet begins to obtain food on its own.

One female is capable of laying more than 120 thousand eggs, the number depends on the size and age of the fish. Sterlet caviar is smaller than that of other sturgeon representatives. Spawning lasts about two weeks, after which the sterlet leaves the riverbeds and enters the floodplains, where it settles in reeds and backwaters to feed. Some adult individuals do not reproduce in every season.

Population and species status

Photo: Sterlet in the wild

Just a few decades ago, sterlet was considered a completely prosperous and numerous species. However, unfavorable environmental conditions, pollution of rivers by runoff, as well as uncontrolled fishing have led to a sharp decline in the number of the species. Therefore, this fish has received the status of a vulnerable species according to the international classification. In addition, the sterlet is listed in the Red Book as an endangered species.

Until the middle of the last century, active fishing for these fish was carried out. Currently, sterlet fishing is strictly limited. However, fish often appears on sale in smoked, salted, canned, fresh or frozen form. The reason for this is that sterlets are actively bred in captivity, on specially equipped farms. Initially, these measures were taken to preserve the biospecies. Then, with the increase in the number of fish in captivity, the revival of the traditions of ancient Russian cooking began.

There are several ways to grow sterlets in cage farms:

Introducing adult fish into cages.
Raising fry. At first, young animals are fed crustaceans, and as they grow older, they diversify their diet with minced fish and mixed feed.
Incubation of eggs - keeping them in special conditions, which leads to the appearance of fry.

Of course, sterlets raised on farms are inferior in taste to fish raised in the natural environment. And their cost is quite high. However, the development of fish farms is a good chance not only for the survival of sterlet as a biospecies, but also for returning its commercial status. Unpretentiousness to food makes it possible to successfully grow fish in artificial conditions. Breeding new species of sturgeon, such as bester, is also beneficial.

The peculiarity of the hybrid is that it combines the advantages of both “parental” species: rapid growth and weight gain - from beluga, early maturation, like sterlets. This makes it possible to quickly reproduce offspring in farm conditions. The most difficult problem is training fish to feed. If you create favorable conditions for them, then in 9-10 months you can grow a five-gram fry into a marketable specimen, the net weight of which is 0.4-0.5 kg.

Photo of sterlet

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