Mostly sturgeon species of fish live in sea s alt water, and swim away to spawn in fresh water. The representatives of the sterlet are endowed with the smallest dimensions, which on average have sizes from 30 cm to 1 m and weight from half a kilogram to 4 kg. The largest representative of the species is the beluga, which reaches 2 tons of mass and 9 m in length.
Today, sturgeon fishing is the world's largest fishery. In addition to meat, this species is also valuable for its caviar. During spawning, fishing is prohibited. But poaching flourishes everywhere, although it is actively fought.
External characteristics and structure
Sturgeon representatives are one of the largest fish in the water expanses of rivers and seas, they have an elongated body, which is covered with five rows of bone scutes: 1 on the back, 2 on the sides and 2 on the belly. Between them are bone plates. Sturgeon is a fish with an elongated cone-shaped snout, similar to a shovel. Below the head are the fleshy lips of the mouth, which in several species has a crescent shape and is also located on the sides. Below the muzzle are 4 antennae. Jawhas a retractable shape without teeth.
The ray fin on the chest is significantly thickened and has the appearance of a spine, while the dorsal fin is slightly pushed back. The swim bladder is located under the spine and is connected to the esophagus. The bone skeleton has an invertebrate, cartilaginous structure with the preservation of the notochord. The membranes of 4 gills are attached to the pharynx and merge at the throat, there are also 2 additional accessory gills.
General information
In most cases, all sturgeon species of fish at the time of spawning move into fresh sources, in shallow water. Their population is quite prolific, and already sufficiently mature and large individuals can produce millions of larvae. Spawning takes place in the spring. It should be noted that some species, in addition to spawning, enter the waters of rivers and winter quarters. They live mainly at the bottom of reservoirs, feed on small fish, worms, molluscs and insects.
Puberty
The sturgeon family, the list of which includes about 2 dozen varieties, is represented mainly by centenarians. The period of readiness of an individual for spawning comes in different ways depending on the habitat and type of fish. At this time, you can observe how the shallow water of some freshwater rivers is simply teeming with sturgeon representatives. After spawning, caviar-producing individuals descend along the river into the sea, increase in size, and develop. The following year, they again go to spawn.
The growth of sturgeon, as well as maturation, is very slow. Some species are ready to breed only inaged 20 years. In females, puberty occurs in the period from 8 to 21 years, in males from 5 to 18 years. But regarding weight, we can say that sturgeon species of fish are the fastest growing inhabitants of reservoirs. The sturgeons of the Dnieper and Don reach puberty the fastest, the inhabitants of the Volga reach puberty much longer.
Spawning
Not all female sturgeons spawn every year. Only the sterlet breeds annually. Representatives of sturgeons spawn in the spring-summer season in the fresh waters of fast-flowing rivers. It has an adhesive structure, so it adheres well to flagstone or pebbles.
Fry
The larvae emerging from the eggs have a yolk sac, which causes the endogenous feeding period. The fry can independently consume external food by the time when the endogenous bladder is completely resolved. Then comes the exogenous period of active nutrition. After that, the fry may linger in the river waters, but often the larvae roll into the sea in the summer of the same year. This is how sturgeons breed. Photos of their various representatives can be viewed in this article.
Feeding fry
The first food for sturgeon fry is zooplankton, such as daphnia. After they begin to eat representatives of crustaceans:
gammarids, chironomids, mysis.
The exception is the predatory beluga fry, which do not have a yolk sac and start eating on their own while in the river.
Further development of sturgeons to sexual maturity occurs in sea waters. Anadromous representatives of sturgeons are divided into spring and winter species. For the former, it is customary to enter the rivers in the spring. Their spawning occurs almost immediately. Winter crops enter the river from autumn, spend the winter, and spawn next spring.
Classification of the sturgeon family
Initially, two genera of sturgeon were distinguished:
sturgeon;
Skafir.
All of them in total numbered about 25 species of fish that were found only in temperate latitudes: Asia, Europe and North America. Over time, the population of some of them disappeared.
Views
Sturgeon species are very popular in the fishery. Today, 17 varieties of sturgeon representatives are known. The most popular types are:
1. Beluga is the most ancient type of freshwater fish. Its life cycle can last 100 years. The largest beluga can reach 5 m in length and have a mass of 2 tons. The body of the fish is similar in shape to a torpedo, covered with protective bone plates in 5 rows, dark gray above and white below. From the bottom of the muzzle there are antennae that provide the scent to the fish, and a sickle-shaped mouth. Females are larger than males. Beluga is a predator that most often feeds on anchovies, gobies, herring, roach and anchovy. Females spawn every 2-4 years in the spring.
2. The Russian sturgeon is a spindle-shaped fish with a short, blunt snout. The antennae are located at the end of the mouth. Most often, the fish has a grayish-black color on top,grayish-brown flanks and white belly. Russian sturgeon reaches a maximum length of 3 m and can weigh up to 115 kg. In this case, the life cycle reaches 50 years. In nature, sturgeon can form hybrids with sterlet, beluga, spike and stellate sturgeon. This happens extremely rarely, but similar hybrids can be found. Fish habitat: Azov, Caspian and Black seas.
3. Siberian sturgeon. The body of the fish is covered with numerous fulcra and bony plates, the mouth is retractable. This fish has no teeth. There are 4 antennae in front of the mouth. Habitats of the Siberian sturgeon: the basins of the Yenisei, Ob, Lena and Kolyma. The maximum fish grows up to 3 m in length, reaches a weight of 200 kg and can live up to 60 years. Spawning occurs in the middle of summer. The sturgeon feeds on organisms that live at the bottom of the river: mollusks, amphipods, polychaete worms and chironomid larvae.
4. The stellate sturgeon lives in the basins of the Azov, Black and Caspian seas. The stellate sturgeon fish is winter and spring. The elongated body of the stellate sturgeon is characterized by the presence of a long nose, a convex forehead, narrow and smooth antennae, and a poorly developed lower lip. From the side and from above the body of the fish is covered with a dense cover of scutes. The back and sides are bluish-black in color, and the belly is white. Sevruga rarely reaches more than 5 m in length and 50 kg in weight.
5. Sterlet is one of the smallest fish among sturgeons, it reaches 1.25 m in length and can weigh up to 16 kg. It has an elongated narrow nose, long antennae that reach the mouth, touching scutes on the sides, and a lower lip divided in two. Excepthabitual for sturgeon plates on the body, the sterlet has closely interlocking scutes on the back. Depending on the habitat, the fish may have a different color, but often its back is a grayish-brown hue, and its belly is yellowish-white. The fins are gray throughout. Also, the sterlet is blunt-nosed and sharp-nosed. The fish is found exclusively in the north of Siberia.
