The Yangtze River sturgeon, known as the king of freshwater fish in China, has received unprecedented public attention in an almost tragic way. Some netizens said that it was extinct when it was first heard of. As of January 4, the topic of the last trace of the Yangtze River sturgeon still occupied the hot search list of a social platform, with nearly 40 million times of reading relevant information.
The Yangtze River white sturgeon is a unique fish of the Yangtze River in China. It has a shuttle like body. Although it is called white sturgeon, only its abdomen is white, and its head, back and tail fins are all cyan gray. Its head is longer than half of its body length, and its snout accounts for nearly three fifths of its head, protruding like a sword.
Adult individuals of the Yangtze River white sturgeon can weigh up to 500 kg, with a body length of 7 meters, which is known as the ten thousand jin elephant in the Yangtze River fishing proverb. According to the records of famous zoologist Bingzhi, 7-meter-long Yangtze River white sturgeon was once caught in Nanjing, which is the highest record of body length of freshwater fish in the world.
Since the late 1970s, due to overfishing and habitat fragmentation, the number of the Yangtze River white sturgeon has declined dramatically. Wei Wei wrote in the above paper that with the rapid decline in the number, since 1989, the Yangtze River white sturgeon has been listed as a national level key protected animal in China; in the red list of endangered species released by the World Conservation Union in 1996, the Yangtze River white sturgeon has been listed as extremely dangerous.
It is understood that the endangered level of the red list of endangered species is divided into 9 levels, extremely endangered represents the degree of endangered next to wild extinction and extinction.
On January 3, the iucnredlist of threatened species is expected to be updated during the World Conservation Conference in June this year, and the final results of the ongoing comprehensive assessment of sturgeons in Asia and Europe have not been released, the iucnredlist of threatened species and the assessment results and corresponding level adjustment will be officially released, the world Conservation Union said on its official microblog.
The following is a dialogue between the reporter of Beijing News and Wei Wei Wei:
No more sightings of Acipenser sinensis in China after 2003
Beijing News: you said in your paper: it is expected that the Yangtze River sturgeon will be extinct by 2005-2010. What is the basis of this judgment?
Wei Qiwei: This is the result of the model calculation. The model is mainly based on the data collected by us, i.e. the past literature; II. We have recorded the fishing records of the white sturgeon in recent decades, including the fishing location, biological information (such as weight, age), etc., and the model is mainly calculated based on these information. In addition, the species is a kind of life body with population and distribution location, which will form field monitoring results. Based on 210 sightings from 1981 to 2003, we estimate that the extinction time of the white sturgeon is from 2005 to 2010.
These data, combined with the model calculation, can deduce the decline degree of a species. Combined with the red list standard of the World Conservation Union, we can judge whether it is a functional extinction or an extinction.
Beijing News: whats the difference between functional extinction and extinction?
Wei Wei: functional extinction means that a species can no longer form a sustainable population in nature. Extinction refers to the complete disappearance of the species in nature.
Beijing News: why is the Yangtze River white sturgeon not artificially bred?
Wei Qiwei: there has been no successful case of artificial culture of the Yangtze River sturgeon. In the past, due to the lack of technology and hardware, the cultured Acipenser schrenckii only survived for 29 days at most. Later, when all the conditions were met, we did not catch the living Acipenser schrenckii. If the rescue pool of the Yangtze River white sturgeon can be repaired earlier and more farsightedly, and it can be raised after being captured, the Yangtze River white sturgeon may still have hope. Now we have made a lot of technical reserves, as long as we can find the living Yangtze River white sturgeon, there is a glimmer of hope.
Beijing News: when was the last time you saw a wild Chinese sturgeon?
Wei Qiwei: on January 24, 2003, we received a message that a fisherman in Nanxi, Sichuan Province mistakenly caught a Yangtze River white sturgeon in the Yangtze River. I immediately led the rescue team to the local area. It was confirmed that it was a female Yangtze River white sturgeon about 4 meters long and weighing more than 150 kg. There were a large number of fish eggs in its belly.
At that time, the Yangtze River white sturgeon was caught by mistake and moved back and forth on the fishermans boat. It had been seriously injured, its abdomen was all congested, and its head and tail were obviously damaged. We disinfected it and sewed up the wound, then placed it on a cage fish boat nearby. After a days cultivation, the injury of the Yangtze River white sturgeon improved. We decided to release it and install ultrasonic tracking equipment on it. We wanted to keep track of it, but then we lost the signal due to the damage of the tracking ship. Since then, there have been no sightings of the Yangtze River sturgeon in China.
Inability to reproduce is the main cause of extinction of Acipenser schrenckii in the Yangtze River
Beijing News: what is the cause of the extinction of the Yangtze River sturgeon?
Unable to reproduce is the main reason for the extinction of Acipenser sinensis. Generally, the Yangtze River white sturgeon spawns in the upper reaches of the Yangtze River and forages for food and fattening in the middle and lower reaches of the Yangtze River. However, the construction of Gezhouba Dam cut off their migration channel in 1981. The larvae of the Yangtze River white sturgeon can still forage in the middle and lower reaches of the Yangtze River through the dam, but the adult Yangtze River white sturgeon can no longer return to the upper reaches to spawn.
The second factor is the development of the fishing industry in the Yangtze River, which makes the big fish and small fish all caught in one net, or directly leads to the death of the Yangtze River sturgeon, or causes the food of the Yangtze River sturgeon to be less and less.
The third is shipping. There are more and more ships, and the waterways are staggered. Not only the propeller of the ship may directly damage the Yangtze River sturgeon, but also the navigation projects derived from shipping, such as waterway regulation, reef blasting, revetment, etc., have a great impact on the habitat of the Yangtze River sturgeon.
Beijing News: what will be the loss or impact of the extinction of the Yangtze River sturgeon?
Wei Wei: the Yangtze River is a large ecosystem, which is composed of tens of thousands of species. These species constitute the biodiversity of the Yangtze River. The extinction of the Yangtze River white sturgeon first means the disappearance of a flagship species in the Yangtze River, which is the loss of biodiversity in the Yangtze River. It is like the death of a very important family member in a large family.
Dont protect it until its functionally extinct.
Beijing News: what is the status quo of other fish in the Yangtze River?
Beijing News: what lessons did the extinction of the Yangtze River sturgeon leave for the protection of rare species in the Yangtze River?
Wei Wei: first of all, some species dont need to wait for their functional extinction to be protected. Its too late. The response of fish to a variety of human threats is lagging behind. Research shows that the critical rescue time for the Yangtze River sturgeon is before 1993 (the year of functional extinction), or at least before 2005 (the year of estimated extinction). But all the substantial rescue work, including underwater sound transmission and trial catching in historical spawning sites, and the research on artificial gynogenesis technology, were carried out after 2006, which was too late.
Now the Chinese sturgeon and the Yangtze River sturgeon are almost extinct. The Chinese sturgeon has not been naturally propagated for the third year, and the Yangtze River sturgeon has not been naturally propagated for 20 years. If it is allowed to develop, they will be the next Yangtze River sturgeon, but at present, their protection has not been implemented at the national level.
Secondly, many dams in the Yangtze River cannot be eliminated in a short period of time, but we can mitigate the impact of other human activities, such as fishing and shipping, which requires all departments to work around the goal of healthy Yangtze River, and each department has its own responsibilities.
In addition, many species in the Yangtze River Basin are considered to be on the verge of extinction, so it is necessary to assess the risk of extinction with various appropriate methods as soon as possible, so as to take appropriate protection measures and determine priorities, so as to avoid more possible extinction.