Acipenser sinensis is a unique fish in China. Its body is spindle-shaped, with five hard scales on its surface, long snout, belly position and crooked tail. This is a marine migratory fish, which goes upstream along the Yangtze River from Haikou to Jinsha River to Pingshan every September-165438+1October. The hatched cubs grow in the river for a period of time, and then return to the Yangtze River estuary for fattening. Every autumn, when ACIPENSER sinensis migrates upstream, a large number of ACIPENSER sinensis can be caught in each river section, so it is known as the "fish king of the Yangtze River". Adult ACIPENSER sinensis is large and heavy, with male weighing 68- 106 kg and female weighing 130-250 kg. It is said that the highest record reached 500 kilograms. Acipenser sinensis also lays a lot of eggs. A female sturgeon can lay 1 million eggs at a time, but the survival rate is not high, and only a few of them become fish. Because the Yangtze River is relatively fast, fertilization is carried out in turbulent water waves, and natural fertilization is incomplete, destroying a number of fish eggs. In the process of hatching, fertilized eggs will lose a lot if they encounter enemies such as carnivorous fish or "surf ashore". Even if it hatches into a small fish, "eat small fish the Big Fish", there will be some losses. Therefore, "three times five divided by two", although there are many ROEs, can "grow into fish" and not many can carry on the family line. In fact, this is the result of reproductive adaptation during animal evolution. In the process of individual development, many species have lost a large number of offspring; On the contrary, it is even less. This is not the arrangement of "God", but those species with less money and greater losses have been eliminated in the long river of history.
Although the Chinese sturgeon is huge, it feeds on Sven, only plankton and plant debris, and occasionally eats small fish and shrimp. According to statistics, the upper reaches of the Yangtze River can produce 20,000 to 30,000 kilograms of Chinese sturgeon every year. However, in recent years, overfishing, coupled with low reproductive rate and long maturity (about 10 year), its population has been decreasing. In order to prevent the extinction of this "living fossil" which is a special product of our country, the relevant departments have listed the Chinese sturgeon as a protected object. But some specific problems still need to be solved. For example, after the completion of the Gezhouba water control project on the Yangtze River, the reproductive migration channel of Chinese sturgeon from Haikou to Jinsha River was cut off, so that pregnant female sturgeons were blocked under the dam and died. How to solve the problem of fishway in dam area is imminent. Fortunately, it is reported that the artificial propagation and release of Chinese sturgeon have been successfully tested. If Chinese sturgeon can settle in fresh water and breed through concrete practice, it will be more practical.
In China, sturgeon fossils were found in the Late Jurassic strata of Beipiao, Liaoning Province (10.40 billion years ago) and named Beipiao sturgeon. This sturgeon has only one line of lateral line scales on both sides, and the other body surfaces are bare, which is different from that of Chinese sturgeon with five lines of scales.
A member of the genus Acipenser. Also known as sturgeon shark, big wax. Named after its origin in China. Body length1.7 ~ 3m; The weight is 40 ~ 378 kg, and the largest individual weighs more than 500 kg. Body spindle. The tip of the kiss is long. The tail is crooked. The body has five longitudinal bone plates with large hard scales. Generally, the head and back of the body are bluish gray or brown, and the abdomen is white. Each fin is blue-gray, and there is a transition zone under the side plate between the side edge and the web.
It is distributed in the northwest Pacific Ocean and Hainan Island in China, east to the Yellow Sea, Bohai Sea and other freshwater rivers such as Pearl River, Qiantang River, Yangtze River and Yellow River. It is a migratory bottom fish. From the sea to the river, I like to gather at the estuary. Mature population 10 ~ 1 10 spawns in deep pools in the upper reaches of rivers and rock deposits in fast-flowing riverbeds. Sexually mature, 9 to 25 years old. The number of fertilized eggs is 47.5 ~ 65,438+0,445,000. Oval, oval, gray-green, sticky. Grow faster. Mainly animal food, generally stopped during spawning.
Sturgeon first appeared in the early Triassic 230 million years ago and has continued to this day.
The sturgeon family once flourished 200 million years ago, and its qualification was older than that of dinosaurs. The modern sturgeon is only their offspring, so the Chinese sturgeon is a famous living fossil, which is of great significance to the study of paleontology and geology.
Acipenser sinensis is an ancient and rare fish unique to China. As early as 1 0,000 BC, the Chinese sturgeon was called the king of tuna. It has a sharp nose and mouth, a small mouth, no teeth and an oval body. There are four tentacles in front of the mouth, which are used to search for invertebrates, small fish and other foods underwater. Acipenser sinensis is a large migratory fish. Like nomads, they were born in rivers and grew up in the ocean, where they grew and developed, and the maturity took about 9- 12 years. When it is fully mature, it will move to the shallow sea area of our country and enter the estuary, where it will be fattened and inhabited. In autumn, it goes upstream along the Yangtze River until it lays eggs and breeds in Jinsha River in the upper reaches of the Yangtze River. After hatching, the young fish follow the expedition of the parent fish and swim to the estuary and the ocean. The life span of Chinese sturgeon is very long, and it can live for one or two hundred years. The fish can be more than 2 meters long, and the female fish weighs about 200 to 300 kilograms. Acipenser sinensis is a precious food, because its meat is very fat and its eggs can be used to make caviar. The swim bladder and notochord can make fish glue, so they were overfished in the past. Many water conservancy projects ignore the ecological balance, which also seriously affects the natural resources of this fish. Now, the Chinese sturgeon is on the verge of extinction and needs strict protection.
In recent years, water pollution is unfavorable to the gonad development, the hatching of naturally propagated fertilized eggs and the growth and development of juvenile ACIPENSER sinensis. Affected by water pollution, the distribution range of juvenile ACIPENSER sinensis in the Yangtze River estuary has been significantly reduced. For example, before 1970s, the juvenile Chinese sturgeon was one of the four main fishing targets in Hangzhou Bay. At present, it is difficult to find traces of juvenile Chinese sturgeon in this water area. Young sturgeons in the Yangtze River estuary also developed liver cancer lesions due to water pollution. After 1980s, the sex ratio in the spawning population of ACIPENSER sinensis was seriously unbalanced, reaching 3: 1 or even 5: 1. The sperm motility of the male parent fish of ACIPENSER sinensis decreased year by year, which may also be directly related to the water pollution of the Yangtze River.
The construction of Gezhouba water conservancy project has also affected the living environment of Chinese sturgeon. Before the construction of this project, the spawning Chinese sturgeon has reached the upper reaches of Jinsha River. After Gezhouba cut off the Yangtze River waterway, the migratory Chinese sturgeon can only reach the dam. The river section of spawning grounds has been reduced from 800km to 7km, and the spawning grounds have been reduced from 16 to 1-2. The spawning grounds area is only 0.4km2, which greatly reduces the migratory number of Chinese sturgeon.
Another reason for the decrease in the number of Chinese sturgeon is artificial fishing. After 1988, although ACIPENSER sinensis was listed as a national first-class protected animal, a considerable number of ACIPENSER sinensis were caught by mistake and illegally every year. Only in Yichang River section, during the period of 1986- 1996, the number of Chinese sturgeon caught and released by fishermen by mistake reached 155, and some fishing gear along the river also seriously damaged the juvenile sturgeon resources. The investigation shows that during the period of 1988- 1992, the total number of juvenile sturgeons caught by mistake is 6350-7060 only in the eastern beach of Chongming Island in the Yangtze River estuary and its extended shoal. In addition, the decrease in the number of Chinese sturgeon is due to the higher age of first sexual maturity, the long interval between repeated reproduction, the low survival rate of fertilized eggs, and the low survival rate of self-reproduction.
According to the investigation data of relevant units, the annual average number of ACIPENSER sinensis migrating by spawning is 2079, 198 1990, 680, 1999, 60 1, and in 2000 it was about 343 and 200. Statistics show that the resources of Chinese sturgeon have dropped sharply and are on the verge of extinction.
In order to protect the breeding of Chinese sturgeon, the state and relevant places have taken various protective measures.
1988 Chinese sturgeon is listed as a national first-class protected animal.
1996, Hubei provincial people's government approved the establishment of Yichang ACIPENSER sinensis nature reserve.
In 2002, the Shanghai Municipal People's Government approved the establishment of the Yangtze River Estuary Juvenile Chinese sturgeon Nature Reserve.
Establish Yichang and Jingzhou Chinese sturgeon protection stations. 1986- 1996 During the ten years, only in Yichang River section, fishermen caught and released Chinese sturgeon 155 by mistake.
A juvenile Chinese sturgeon rescue station has been established to rescue and nurse the injured juvenile Chinese sturgeon by mistake, which can rescue several ten tail to hundreds of juvenile Chinese sturgeon released every year.
Carry out artificial breeding and release the young sturgeon to the Yangtze River. In 1970s, artificial propagation of Chinese sturgeon in Jinsha River spawning ground was initially successful, with a small amount released. During the period of 1983, the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences and other units successfully carried out artificial propagation and artificial release under Gezhouba. Since then, the former Chinese sturgeon research institute of the Ministry of Water Resources has also successfully carried out artificial propagation. Due to the maturity of artificial breeding technology of Chinese sturgeon, especially the maturity of artificial storage and breeding of Chinese sturgeon, it can be released in a planned way, and the continuous improvement of Chinese sturgeon breeding technology makes it possible to release it artificially on a large scale. At present, the labeling method can also distinguish between artificially released and naturally propagated young sturgeons.
Since 1997, the Yangtze River Fisheries Research Institute has made a new breakthrough in the breeding technology of ACIPENSER sinensis, and the survival rate of large-scale breeding of ACIPENSER sinensis has reached over 80%. 1998 bred about 80,000 juvenile Chinese sturgeon with a body length of 12-20 cm, which greatly broke the historical record and laid the foundation for large-scale artificial release.
From 1983 to 1998, several scientific research institutes released about 5.8 million Chinese sturgeons of various specifications to the Yangtze River, Minjiang River, Pearl River and other waters. By the end of 2004, about 600,000 Chinese sturgeon fry with a size of 65,438+00 cm had been released into the Yangtze River. Since 198 1 year, more than 6 million Chinese sturgeons of various specifications have been released, and more than 0/000 Chinese sturgeons of large specifications have been released.