The European sturgeon is distributed in the Caspian Sea, the Sea of Azov, the Black Sea and the Adriatic Sea. The Caspian Sea is mainly distributed in the Volga River, the Ural River and its tributaries, the Black Sea is mainly distributed in the estuary of the east coast rivers, such as the Danube River, the Dnieper River and the Dniester River. The Sea of Azov is mainly located in the Don River. The European sturgeon also inhabits the Kura, Czech Republic and Kuban rivers. The European sturgeon is the earliest anadromous among sturgeons and is divided into two populations and winter and spring populations. Spawning migration in the Danube is observed almost the whole year. The spring migratory type anadromous in January-April, the water temperature of 4-5 ° C begins to migrate, spawning in the same year. The fall migratory type begins anadromy in August, reaches its peak in October-November, and spawns the following year, with the fall migratory type dominating the population. In the Caspian Sea the spring migratory type is anadromous in March-April, the fall migratory type is anadromous in September-October. In the Volga River the winter population is dominant; in the Ural River, on the contrary, the spring population is dominant, accounting for about 70%. The migration distance of the European koala is 940-1810 kilometers.
1 European koala Husohuso (Linnaeus, 1758)
The fish is a huge individual, fusiform, thinning towards the tail, with a body height of 9%-22% of the total length. Individuals grow to a full length of up to 6 meters, weighing more than 1000 kilograms. European sturgeon head length of about 23% of the total length, kiss length of 7%-12.5% of the total length. The muzzle is short, soft, tapered and cartilaginous; the mouth is prominent, crescent-shaped, located on the ventral surface of the head, extending to the sides. The whiskers are 4, longer, laterally compressed, with leaf-like cilia attached to them. Gill rakers 17-36, European sturgeon body surface covered with 1 layer of soft skin, bone plate 5 rows, dorsal plate 9-17, ovoid, longitudinal split like a serrated comb, the first dorsal plate is the smallest. Lateral plates 37-53, smooth; ventral plates 7-14, hidden under the skin. Rows of plates with numerous small plates and granules distributed on the body surface; rows of plates not connected caudally. Dorsal fin unbranched, fin rays 48-81; anal fin unbranched, fin rays 22-41; caudal peduncle not laterally compressed. The European sturgeon is greenish gray on the back and sides of the body, sometimes black, gradually turning white downwards. Its belly is white and its muzzle is yellow. Juvenile European sturgeon prey on aquatic insect larvae, herring and fish are fish, larger individuals prey on waterfowl, young seals and fish, and adults generally feed mainly on fish.
1.3 Growth and reproduction
The European sturgeon grows rapidly, averaging 51 centimeters in total length and 571 grams in average weight at age 1 in the Caspian Sea, and 40 centimeters in total length and 250-500 grams in average weight at age 1 in the northwestern Black Sea and Sea of Azov. In the following years, the growth of European sturgeon in the Black Sea and Sea of Azov gradually exceeded that of the Caspian Sea. In Black Sea females, age 3 fish were 106 cm in total length and 62 kg in weight, age 5 fish were 121 cm in total length and 96 kg in weight, and age 10 fish were 163 cm in total length and 259 kg in weight. Mature females are 230-270 cm in total length and 90-120 kg in weight, and mature males are 180-220 cm in total length. Sexual maturity of the European sturgeon is late. In the Caspian Sea in recent years migratory females were 14-28 years old and males 11-16 years old. Sex ratio of migratory fish is 1:1, the age of sexual maturity of the Volga River European koala females for the first time 16 years old, mostly in the age of 19-22 years, and males for the age of 11 years old, mostly in the age of 14-16 years. Female spawning period of more than 5 years, spawning water temperature 6-7 ℃, water temperature 21 ℃ to stop spawning, the appropriate water temperature of 9-17 ℃. Egg diameter 3.33-3.84 millimeters, egg weight 295 milligrams, maturity coefficient of 13.2%-17% of the female fish, the average male fish 3.9%, the amount of eggs 500,000-800,000 grains, up to 2.7 million grains.
2 Russian sturgeon AcipensergueldenstaedtiBrandt, 1833
2.1 Morphology and diet
The fish is individually prolonged, fusiform, with a body height of 12-14% of the total length. In the Black Sea, individuals can reach 236 centimeters in total length, weighing 115 kilograms, and up to 300 centimeters in total length. In the Caspian Sea, its individual length can reach 215 centimeters, weight 65 kilograms, the maximum length of 235 centimeters. Russian sturgeon head length is 17%-19% of the total length, the length of the muzzle is 4%-65% of the total length, the muzzle is short and blunt, slightly rounded. 4 tentacles are located between the end of the muzzle and the mouth, closer to the end of the muzzle. No umbrella-shaped cilia on the whiskers. The mouth is small, transverse and more prominent, with the lower lip disconnected in the center. In the Kula River, its mouth width averages 30.8% of head length. Gill rakers non-fan shaped, number of gill rakers 15-31. body covered with 5 rows of bony plates, between the rows of bony plates distributed on the surface of the body many small bony plates often called small star. There are 8-18 dorsal plates, 24-50 lateral plates, and 6-13 ventral plates. The dorsal fin is unbranched, with fin rays 27-51; the anal fin is unbranched, with fin rays 18-33. body coloration is grayish-black, light green, or dark green dorsally, usually grayish-brown laterally, and grayish or a little lemon-yellow ventrally. Juveniles have a blue dorsal coloration and a white belly. In the northwestern part of the Black Sea, the Russian sturgeon feeds mainly on benthic mollusks, but also on shrimps, crabs and other crustaceans and fish. In the Sea of Azov, adults feed mainly on molluscs, polychaetes and fish. In the Danube, juveniles feed on mysid shrimp and larvae of rockhopper. In the Caspian Sea, the composition of their food varies slightly at different times.
2.2 Distribution and migration
The Russian sturgeon is mainly found in the Caspian Sea, the Sea of Azov and the Black Sea, as well as in the rivers that flow into these waters. Such as the Kura, Ural, Terek, Volga, Kuban, Don, Dnieper, Dniester and Danube rivers. In addition to migratory populations, some of the Russian sturgeon are sedentary populations that spend their entire lives in freshwater. There are sedentary populations inhabiting the Volga River. The anadromous migration of Russian sturgeon in the Caspian and Black Seas begins in early spring, peaks in mid- and late summer, and ends in late fall. In the Volga River, spawning migrations begin in late March or early April, when the water temperature is 1-4°C, and spawning populations peak in June-July. When the water temperature drops to 6-8 ℃ anadromous population gradually decreases, until November basically stop.
Spring migration type spawning in the current year, fall migration type spawning in the following year. The spring migration type usually migrates only 100-300
km away from the estuary, while the fall migration distance is thousands of kilometers away from the estuary.
2.3 Growth and reproduction
Russian sturgeon grows fastest in the Sea of Azov and slower in the Caspian and Black Seas. Migratory populations grow faster than sedentary populations, and females grow faster than males. In the Sea of Azov Russian sturgeon age 1 fish length 294 cm, age 2 fish length 462 cm, weight 2 kg, age 5 fish length 666 cm, weight 55 kg, age 10 fish length 908 cm, weight 12 kg. Russian sturgeon males first sexual maturity age in 7-9 age, full length of 100 cm or more.
Females mature at 12-16 years of age, and males mature at 11-13 years of age. In the Volga River females spawn for 4-5 years and males for 2-3 years. In the Danube River the interspawning period for females is 5-6 years. Mature females in the Volga weigh 14-18 kg, maturity coefficient 141%. Spring migratory type reproduces from mid-May to the beginning of June, the water temperature 89-12 ℃. In the Sea of Azov Russian sturgeon sexual maturity is advanced by 1-2 years. Volga River females absolute egg carrying capacity average value of 2.66-2.94 million, relative egg carrying capacity per kilogram of fish body weight 10,800-12,000, egg diameter 2.8 × 3.2-3.3 × 3.8 mm, egg grain weight 20.6 mg.
3 Naked Belly Sturgeon AcipensernudiventrisLovetzky, 1828
3.1 Morphology and diet
Individuals of the fish are long-bodied, with a body height of 12.3-161% of the total length. In European waters, individuals can reach 221 centimeters in total length and weigh 80 kilograms; the largest individual weighs 127 kilograms. Individuals of Acipenser sturgeon have a head length of 191%-22.2% of total length and a snout length of 32.2%-43.6% of head length. The snout is smooth, slightly rounded, almost a complete cone. The mouth is relatively large, the lower lip is not open in the middle, and the mouth is located on the ventral surface of the head. Naked belly sturgeon has 4 tentacles, with cilia on the tentacles, the length of the tentacles is 71%-176% of the head length; the number of gill rakers is 24-45.The body of the fish is covered with 5 rows of bony plates, and there is no distribution of small bony plates between the rows of bony plates on the surface of the body. The first dorsal plate is the largest, forming an obtuse angle with the top surface of the head. There are 11-17 dorsal plates, 49-74 lateral plates, and 11-17 ventral plates. Dorsal fin rays are unbranched, 39-57; anal fin rays are unbranched, 23-37. The naked sturgeon is grayish-green on the back, lighter on the sides, yellowish-white on the belly, and all fins are gray. In the Danube River, the naked belly sturgeon feeds on mayfly larvae, and other foods include aquatic insects, mollusks and crustaceans, etc. In the Caspian Sea, the naked belly sturgeon feeds on fish in the early days, and in recent years, due to the migration of crabs, the crabs accounted for about 70% of its food intake.
3.2 Distribution and Migration
The sturgeon is found in the Black Sea, the Sea of Azov and the Caspian Sea, and after sexual maturity, it goes upstream to rivers to spawn.
In the Black Sea, the main spawning grounds of the sturgeon are in the Danube River system, more than 1766 kilometers from the river mouth. In the Caspian Sea the sturgeon mostly inhabits the southern part, the main upstream rivers are the Kura and its tributaries, 650 kilometers from the mouth of the sea. In other rivers of the southern part of the Caspian Sea the sturgeon also occurs occasionally. In the Sea of Azov the sturgeon is rare. The sturgeon is divided into migratory and sedentary populations, with the sedentary population living in freshwater all year round. The Kura River sturgeon has two migrations per year, in April-May, when the water temperature rises to 62-13 ℃, the spring migratory population began to anadromous.
In October-November, when the water temperature is 12-179 ℃, the fall migratory type begins anadromous, anadromous migration is about 600 kilometers from the river mouth. The Ural River has only spring migratory type, in April-May, when the water temperature rises to 3.2-45 ℃ began anadromous, migratory distance is mostly in the 500-800 kilometers, however, some individuals of the spawning ground is more than 100 kilometers from the mouth of the river.
3.3 Growth and reproduction
Naked Belly Sturgeon grow faster, and females grow faster than males. In the Caspian Sea, the average length of 1-year-old males is 282 centimeters, weighing 40-60 grams, 2-year-old fish is 45 centimeters long, weighing 350 grams, and 5-year-old fish is 778 centimeters long, weighing 1.8 kilograms. Naked belly sturgeon populations in the Caspian Sea are large individuals, and the life span is usually 30-32 years. The age of first sexual maturity of the Kura River sturgeon is 12-14 years in females and 6-9 years in males. The spawning population of the Kura River consists of about 92% of females at 14-19 years of age and about 96% of males at 9-16 years of age. The age of first sexual maturity in the Ural River is 16-22 years in females and 13 years in males. In the spawning group in the Ural River females were 15-18 years old, 80%; males 9-14 years old, 44%. The interspawning period of females is 2-3 years. The absolute number of eggs carried by Danube females is 200,000-1,300,000, and 1,650,000-715,000 for Ural River females. Eggs of Aral Sea females weigh 11.4 mg, egg diameter 1.55-3 mm. Kura River spawning water temperature 15-25°C, spawning in March-May, egg grain weight 12.44-1475 mg. Danube spawning water temperature 10-15 ℃.
4 Flash sturgeon AcipenserstellatusPallas, 1771
4.1 Morphology and diet
The fish is individually in the form of a long fusiform body, which reaches a maximum total length of 218 centimeters and a weight of 54 kilograms. Flash sturgeon is usually 100-120 centimeters in length and weighs 6-8 kilograms. Flash sturgeon kiss long and thin, its dorsal and ventral flat, the kiss length of 59% -65% of the head length. The mouth is transverse, moderately wide, and the lower lip is broken in the middle. Whiskers 4, short, no cilia attached. The gill membrane reaches the isthmus, and the number of gill rakers is 24-29. flash sturgeon have 5 rows of bony plates, and the body surface is covered with stellate small bony plates and pectinate granules. Ctenoid granules sometimes dominate, when the small plates are distributed in the rows of plates. The dorsal plates are arranged in radial stripes and form a tough spine together with the straight tail tip. The dorsal plates are 9-16 in number, the highest being located on the 3rd plate or between the 3rd and 7th plates. Lateral plates 26-43, ventral plates 9-14. The dorsal fin is notched, unbranched, and has 40-54 fin rays; the anal fin is blunt or slightly notched, unbranched, and has 22-35 fin rays; the dorsal and lateral sides of the body of the sturgeon are dark blackish brown, the abdomen is light-colored, and the ventral plates are off-white. Flash sturgeon are usually yellowish brown or greenish gray dorsally. In some cases, the dorsal part of the body is nearly black, the lateral part of the body is lighter in color, and the proximal part of the bony plate is yellowish-white. In the Caspian Sea, juvenile sturgeon feed on crustaceans, and adults feed on fish. In the Azov Sea flash sturgeon recipe worms accounted for 35%-60%, mollusks accounted for 15%-30%, fish accounted for 30%-50%.
4.2 Distribution and Migration
Flash sturgeon are mainly found in the Caspian Sea, the Sea of Azov, the Black Sea and the Aegean Sea, as well as in the rivers that connect with them. The largest population of the flash sturgeon inhabits the Caspian Sea, and the main rivers into which it enters are the Volga, the Ural, the Kura and the Surak. It also inhabits some rivers in the southern part of the Caspian Sea, and in the Sea of Azov inhabits the Don and Kuban rivers and their tributaries. Flash sturgeon in the Volga River in mid-April (at this time the water temperature of 6-9 ℃) began anadromous, the peak period in May (at this time the water temperature of 10-15 ℃), in June the anadromous activity decreases. Flash sturgeon in August, September, October anadromous activities increased again, ended in November. Flash sturgeon in the Ural River in April-May (at this time the water temperature of 54-72 ℃) began anadromous, followed by water temperature increases to 12-14 ℃ when the peak. Fall migration begins in late August to mid-October, with a peak in September.
4.3 Growth and reproduction
In the Don River, the flash sturgeon at the age of 1 is 25 centimeters long and weighs 0.5 kilograms, and at the age of 2 is 57 centimeters long and weighs 1 kilogram. Flash sturgeon length growth is fastest in the first year, and the fastest growth rate is in the second year. Subsequently, the rate gradually decreases until sexual maturity, and mature females grow faster than males. In the Volga River flash sturgeon 17-18 years old male and female body average length difference of 12 centimeters, weight difference of 44 kilograms.
Female Volga River sturgeon first sexual maturity 11 age, mostly in the 11-15 age, full length 123 cm; male fish 8 age, mostly in the 9-12 age, full length 106 cm. In the Kuban River, females first reached sexual maturity at 6 years of age, mostly at 8-10 years of age, with a total length of 114 cm; males at 4 years of age, mostly at 5-6 years of age, with a total length of 93 cm. In the Don River, females first mature at age 7, mostly at age 9-11, with a total length of 129 cm; males at age 5, mostly at age 7-8, with a total length of 112 cm. 10-15 kg females carry 80,000-180,000 eggs, and 15-20 kg females carry 150,000 eggs. Egg diameter 2.7-3.2 millimeters, egg weight 10-14 milligrams.
5 Small-bodied sturgeon Acipenserruthenus Linne, 1758
5.1 Morphology and diet
Individuals of the fish are elongated, with a body height of 59-166% of the total length. Individuals reach a maximum total length of 125 centimeters and weigh 16 kilograms. Usually individuals are less than 100 centimeters in total length and weigh less than 65 kilograms. Small-bodied sturgeon head length is 146%-30.5% of total length. Snout length varies significantly, in different waters its snout length varies from 278% to 63.5% of the head length. The mouth is small and transverse, the lower lip is broken in the middle, and the width of the mouth is 12%-269% of the head length. Tentacles 4, located on the ventral surface of the head, with umbrella-shaped cilia attached to the whiskers; number of gill rakers 11-27.
Small-bodied sturgeon with 5 rows of bony plates, dorsal bony plates 11-18, lateral bony plates 56-71, ventral bony plates 10-20, with a large number of small bony plates distributed between the rows of bony plates on the surface of the body. The dorsal fin is unbranched, with fin rays 32-49; the anal fin is unbranched, with fin rays 16-34(39); and the ventral fin is unbranched, with fin rays 25-45.The body color of the small-bodied sturgeon varies greatly, with the dorsal surface often appearing a dark grayish-brown color, and the abdomen a yellowish-white color. Small-bodied sturgeon feed on benthic organisms in rivers, mainly aquatic insect larvae, crustaceans and small mollusks. In the fish spawning period, small-bodied sturgeon to other fish eggs and other sturgeon eggs for food, sometimes eggs accounted for more than 50% of its intake. Juvenile fish and adult fish diet is slightly different, 6 months of age small body sturgeon juveniles mainly eat Trichoptera and mosquito larvae, with the growth of the individual ingestion of mosquito larvae the number of gradual decrease in the number of mosquito larvae, while the number of Trichoptera increased.
5.2 Distribution and migration
Small-bodied sturgeon are widely distributed in Russia and Europe, mainly inhabiting rivers flowing into the Caspian Sea, the Black Sea, the Sea of Azov, the Baltic Sea and the White Sea. Rivers and tributaries such as the Volga, the Ural, the Kura, the Obi, the Kuban, the Don, the Dnieper, the Dniester and the Danube. Small-bodied sturgeon also inhabit lakes. Small-bodied sturgeon are partly sedentary species, in addition to migratory species. Migratory species of small-bodied sturgeon start spawning upstream during the spring flood season, the larger the water body during the flood season, the more spawning groups, the further the anadromous, and the migration lasts 4-5 weeks. When the river level drops, the anadromous group decreases, and then the small-bodied sturgeon swim to the spawning ground to spawn. After spawning, the parent fish gradually descended to the river to the harbor, bay, branch, river and other bait-rich water areas to feed, fertilization.
5.3 Growth and reproduction
Small-bodied sturgeon in the Danube River system is the fastest-growing, the age of 1 fish length of 258 centimeters, weighing 142 grams, age 2 fish length of 37 centimeters, weighing 264 grams, the age of 5 fish length of 52.9 centimeters, weighing 798 grams, the age of 9 fish length of 661 centimeters, weighing 1806 grams. The maximum age of small-bodied sturgeon is known to be 27 years old, with a maximum total length of 84 cm and weight of 43 kg. Females have a longer life span than males. Small-bodied sturgeon reach sexual maturity earlier, males 1-2 years earlier than females, and in the Danube River system females reach first sexual maturity at 4-7 years of age and 40 cm in total length, and males at 3-5 years of age and 40 cm in total length. In the Volga River, the first sexual maturity of females is 34 cm at age 7, and of males 28 cm at age 4. The maturity coefficient of females is 16%-18%, males 2%-4%, and the water temperature for spawning is 12-17℃. Small-bodied sturgeon maximum carrying capacity of 100,000 eggs, egg diameter 2.01 × 1.85-2.86 × 2.77 mm, egg weight 8-9 mg, mature eggs black and gray. The Volga River small-bodied sturgeon fawns can reach 6-7 millimeters in full length at 6-10 days, 3-4 centimeters after 1 month, and up to 25 centimeters in the same year.
--Cited from: Luo Xiangzhong Biology of the Major Species of European Sturgeoniformes Freshwater Fisheries, 1999-29(1). -24-27
5.4 The rumored giant sturgeon
How huge can the sturgeon be? In 1827, a sturgeon was allegedly caught at the mouth of the Volga River, measuring 7.2 meters in length and weighing 1,476 kilograms, which far surpassed the records of the Mekong giant catfish and the giant bony tonguefish.