Mostly sturgeon species of fish live in sea salt water, and swim to fresh water for spawning. 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 Beluga, which reaches 2 tons of mass and 9 m in length.
Today, sturgeon fishing is the largest fishing industry in the world. In addition to meat, this species is also valuable for its caviar. During spawning, fishing is prohibited. But poaching is thriving everywhere, even though they are actively fighting it.
External characteristics and structure
Representatives of sturgeons are one of the largest fish in the water of rivers and seas, they have an elongated body, which is covered by five rows of bone scutes: 1 on the back, 2 on the sides and 2 on the belly. Bone plates are located between them. Sturgeon is a fish with an elongated cone-shaped snout similar to a shovel. Bottom of 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 there are 4 antennae. The jaw has a retractable shape without teeth.
The radial fin on the chest is significantly thickened and looks like 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 chord. The membranes of 4 gills are attached to the pharynx and merge on the throat, there are also 2 more accessory gills.
general information
In most cases, all sturgeon species at the time of throwing eggs go to freshwater sources in shallow water. Their population is quite prolific, and already enough adults and large individuals can produce millions of larvae. Spawning occurs in the spring. It is worth noting that some species, except spawning, enter the waters of rivers and in the winter. They inhabit mainly at the bottom of reservoirs, feed on small fish, worms, mollusks 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 throwing eggs begins differently depending on the habitat and type of fish. At this time, one can observe how the shallow waters of some fresh rivers are simply teeming with representatives of sturgeons. After spawning, individuals producing eggs descend along the river into the sea, increase in size, and develop. The next year, they again go to spawn.
Sturgeon growth, as well as maturation, is very slow. Some species are ready for breeding only at the age of 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 are the fastest growing inhabitants of water bodies. Sturgeons of the Dnieper and the Don reach the puberty the fastest; the inhabitants of the Volga are much longer.
Spawning
Not all sturgeon females spawn every year. Only sterlet is propagated annually. Representatives of sturgeon spawn in the spring-summer season in the fresh waters of fast-flowing rivers. It has an adhesive structure, therefore it is perfectly attached to flagstone or pebbles.
Fry
Larvae emerging from eggs possess a yolk sac, which causes an endogenous feeding period. Fry can independently consume external food by the time the endogenous bladder is completely absorbed. Then the exogenous period of active nutrition begins. After this, the fry can linger in river waters, but often the larvae slide into the sea in the summer of that year. So sturgeon breed. Photos of their various representatives can be found in this article.
Fry nutrition
The first food for sturgeon fry is zooplankton, for example, daphnia. After they begin to eat representatives of crustaceans:
* gammarides,
* chironomids,
* mysids.
The exception is predatory beluga fry, which do not have a yolk sac and even during their stay in the river begin independent eating.
Further development of sturgeon until adulthood occurs in seawater. The migratory representatives of sturgeon are divided into spring and winter species. For the former, entry into rivers in the spring is common. They spawn almost immediately. Winter crops enter the river in the autumn, spend the winter, and spawn already next spring.
Classification of the sturgeon family
Initially, two genera of sturgeon were distinguished:
* sturgeon;
* scafirins.
In total, they totaled about 25 species of fish that were found only in temperate latitudes: Asia, Europe and northern America. Over time, the population of some of them disappeared.
Kinds
Sturgeon species are very popular in the fishery. To date, 17 species of sturgeon are known. The most popular types are:
1. Beluga - the oldest species 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 looks like a torpedo in shape, covered with protective bone plates in 5 rows, dark gray above and white below. Beneath the muzzle there are antennae providing a smell to the fish, and a mouth in the shape of a sickle. Females are larger than males. Beluga is a predator that feeds most often on anchovies, bulls, herring, roach and hamsa. Females throw eggs every 2-4 years in the spring.
2. Russian sturgeon - fish with a fusiform body with a short blunt snout. Antenna located at the end of the mouth. Most often, the fish has a grayish-black color on top, grayish-brown sides and a white belly. Russian sturgeon reaches a maximum of 3 m in length and can have a weight of up to 115 kg. Moreover, 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 bone plates, the mouth is retractable. The teeth of this fish are missing. There are 4 antennae in front of the mouth. Siberian sturgeon habitats: the Yenisei, Ob, Lena and Kolyma basins. 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. Organisms living on the bottom of the river serve as food for sturgeon: mollusks, amphipods, polychaete worms and chironomid larvae.
4. Stellate sturgeon lives in the basins of the Azov, Black and Caspian seas. Stellate sturgeon fish can be winter and spring. The elongated body of stellate sturgeon is characterized by the presence of a long nose, a convex forehead, narrow and smooth antennae, and a poorly developed lower lip. Side and top of the body of the fish is covered with a dense cover of scutellum. The back and sides are bluish-black, and the belly is white. Stellate sturgeon rarely reaches more than 5 m in length and 50 kg of weight.
5. Sterlet - one of the smallest fish among sturgeons, it reaches 1.25 m in length and weighs up to 16 kg. It has an elongated narrow nose, long antennae that reach the mouth, adjoining scutes on the sides and a lower lip divided in two. In addition to the sturgeon plates that are familiar to the body, the sterlet has closely closed scutes on its back. Depending on the habitat, the fish may have a different color, but often its back is grayish-brown in color, and the belly is yellowish-white. The fins are ubiquitously gray. Also, the sterlet is blunt and pointed-nosed. Fish is found exclusively in the north of Siberia.