Chinese sturgeon (scientific name: acipenser sinensis): Is a fish of the family Bonyosauridae. Common individuals are 50-300 kg, the largest individual can reach 600 kg, the average body length is about 40 cm, and the maximum length is 230 cm. It is the largest fish in the Yangtze River, so it is known as the "Fish King of the Yangtze River". The body is spindle-shaped, the tip of the head is long, there are 4 snouts in front of the mouth, the mouth is located on the ventral surface, it is elastic, and it can be stretched into a barrel, and the body is covered with five large and hard bone scales, one row on the back, two rows on the body side and two lines on the ventral side. The caudal fin is crooked-tailed, with a broad base of the even fin and a dorsal fin opposite the fin. The ventral fin is located in front of the dorsal fin, the base of the fin and caudal fin has spinous scales, the intestine has a spiral valve, the anus and cloaca are located near the base of the ventral fin, and the opening of the fallopian tube is far from the ovary.
Chinese sturgeon is a benthic fish, very narrow feeding habits, carnivorous fish, mainly feeding on some small or slow-moving benthic animals, in the ocean mainly feeds on fish, followed by crustaceans, and fewer molluscs. Chinese sturgeon juveniles feed mainly on benthic fish snakefish and pupae, as well as scaly shrimp and clams, and generally stop eating during spawning.
In the summer and autumn, the Chinese sturgeon living in the shallow waters outside the mouth of the Yangtze River swam back to the Yangtze River, and after more than 3,000 kilometers of tracing and attacking, they returned to the Jinsha River to spawn and breed. After giving birth, the juveniles grow to about 15 cm and carry them to live in the open sea. They have been born in the upper reaches of the river for generations and grow in the sea.
Chinese sturgeon has a long life cycle, with a maximum lifespan of up to 40 years old. It is a first-class key protected wild animal in China, and it is also a living fossil, known as the "giant panda in the water". It has high scientific research, medicinal and ornamental value. It is found in China, Japan, South Korea, the Lao People's Democratic Republic and North Korea. It is mainly distributed below the Jinsha River, the main stream of the Yangtze River in China, to the mouth of the Haihe River, and other river systems such as the Ganjiang, Xiangjiang, Minjiang, Qiantang and Pearl Rivers have occasionally appeared.
The Chinese sturgeon is powerful, large and long-lived, with the longest lifespan of up to 40 years old, making it the largest and longest-lived fish among freshwater fish. After entering the river, the Chinese sturgeon must stay in the river for one year and arrive at the spawning site in October of the following year. During the year, the Chinese sturgeon did not always follow the river, but stopped swimming from time to time, sometimes lurking in the potholes of the river for several days. In the autumn of the following year, it traces up to the rapid flow of the upper reaches of the river and the bottom is gravel, and the breeding groups gather in the spawning grounds to breed.
Chinese sturgeon is a benthic fish, which is an omnivorous fish mainly based on animal food, mainly feeding on some small or slow-moving benthic animals, including shrimp and crabs, fish, molluscs and aquatic insects. Due to the different food types of living environments, juvenile fish in the middle and upper reaches of the Yangtze River mainly feed on mosquito larvae, dragonfly larvae, ephemeral larvae and plant detritus, while juvenile fish in the brackish water area of the estuary feed on shrimp, crabs and small fish. Broodstock are not fed during migration. In the offshore waters off the yangtze River estuary, the feeding intensity of Chinese sturgeon increases, usually in the 3-4 grade, and the food is mainly fish and crabs, as well as shrimp and cephalopods.
The Chinese sturgeon is a typical river-retrograde migratory fish. It usually lives in the coastal continental shelf area of the East China Sea and the South China Sea, and grows and develops in the sea. When males reach 9 to 18 years of age, with a body length of 170 cm and a weight of more than 50 kg, and females reach primary sexual maturity when they reach 14 to 26 years of age. Individuals that begin to mature enter the river from the sea in July and August, and gradually develop their gonads in freshwater habitat for one year.
According to studies, in spawning groups, males are generally 9-22 years old and weigh 40-125 kg; females are 16-29 years old and weigh 172-300 kg It has been observed that the average annual growth rate of Chinese sturgeon is faster, with males 5-8 kg and females 8-13 kg. However, it takes 8-14 years to grow from juvenile to large adult. When it reaches its initial sexual maturity later, it can reproduce offspring.
In the spawning population, the males are 9-22 years old, 1.7-2.4 m long and 40-125 kg in weight, while the females are 16-20 years old, 2.4-3.1 m long and 172-300 kg in weight. The amount of eggs conceived is large, and the absolute number of eggs conceived by individuals is 306,000-1.303 million, with an average of 645,000 eggs. Spawning in the upper reaches of the river from September to November. The spawning period needs to be in a river with a water temperature of 18.0-20.5 °C, a sand content of 0.715-0.915 kg/m3, a flow rate of 2.2-2.6 m/s, a transparency of 4-6 cm, ph8, a dissolved oxygen volume of 9.2 m l/l, and a water depth of 5-19.8 m. The spawning grounds that are more concentrated in the Yangtze River are in the Yibin-Pingshan section of the Jinsha River. It is a type of one-time ovulation. Produces sticky sinking eggs, which stick to the gravel and hatch. Mature eggs are oval in shape and greenish brown. The egg diameter is about 3.6 mm. Fertilized eggs hatch after 123-140 hours at water temperature 17-18 °C. Most broodstock quickly leave spawning grounds and inhabit downstream and estuarine areas.
Soon after spawning, the female broodstock begin to descend into the river. The broodstock basically stop feeding during reproduction, and the eggs produced are sticky, adhere to the rocks or gravel at the bottom of the river, and under the conditions of water temperature of 17-18 ° C, the fertilized eggs hatch for about 5-6 days and nights. Newly emerging hatchlings have a large yolk sac, shaped like tadpoles, drift down the water and start feeding after about 12-14 days. In the spring of the following year, the young sturgeon gradually descended into the river, appearing in the Chongming Island area of the Yangtze River estuary from May to August, and after September, the young sturgeon, which has reached a length of 30 cm, have left the shallow mudflats at the mouth of the Yangtze River and entered the sea to cultivate and grow. The life cycle is long, with a maximum lifespan of up to 40 years.
academic
The Chinese sturgeon is the oldest vertebrate on Earth and is a descendant of the ancient spiny fish, the common ancestor of fish, with a history of 140 million years. Lived in the same period as dinosaurs. Due to their own series of primitive characteristics, Chinese sturgeon shows that they are not only between cartilaginous fish (sharks, etc.) and teleost fish, but also the more primitive taxa of teleost fish, which has important academic value in the evolutionary history of fish. The Chinese sturgeon occupies an extremely important position in taxonomy, is an important reference for the study of fish evolution, and has important scientific value and immeasurable ecological, social and economic value in the study of biological evolution, geology, landform, transgression, sea retreat and other aspects of earth changes. However, due to various reasons, this rare animal is on the verge of extinction. Protecting and saving this rare and endangered "living fossil" is of far-reaching significance for the development and rational development and utilization of wildlife resources and the maintenance of ecological balance. From it, some traces of biological evolution can be seen, so it is called a living fossil in aquatic life.
economy
Chinese sturgeon is a large economic fish, and both meat and eggs are edible. High in fat protein. Maws and notochords can be made of glue, and the fins and lips are also multi-gummy. In addition, it has high academic value, because it is a remnant of the Cretaceous period, endemic to China, and has been listed as a class of wildlife protected species in China. In order to protect this species, the relevant departments have carried out many years of research on breeding, migration, and stocking. It can now be moved to ponds and reservoirs, where it grows well and becomes a promising freshwater farmed fish. The results of the release were also considerable, and by 1992 more than 1 million had been released, gradually increasing the amount of resources.