◎ Author | Science and Technology Daily reporter Zhang Galen
◎ Edit | Liu Li
For the fourth consecutive year, scientific research institutions have not monitored the natural spawning of Chinese sturgeon.
Without eggs, there is no possibility of giving birth to new life.
Wei Qiwei, a researcher at the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences and a member of the Sturgeon Expert Group of the IUCN Species Survival Committee, confirmed this bad news in an interview with a reporter from Science and Technology Daily. The interruption of natural reproduction has become the biggest dilemma faced by this ancient species of Chinese sturgeon.
Chinese sturgeon specimen in the Museum of Hydrobiology, Chinese Academy of Sciences. Science and Technology Daily reporter Zhang Galen / photo
"The situation is not optimistic." He sighed, "Possibly, the Chinese sturgeon just left." ”
"The natural population has been severely degraded and its living conditions are very endangered", "The ancient sturgeon seems to be caught in the extinction vortex", "The wild population of the Chinese sturgeon has reached the brink of extinction"... Looking at the papers published in recent years, it will be found that authors from different scientific research units have described the current situation of Chinese sturgeon with some sighs and sorrows.
But fortunately, the window of protection has not been closed.
In mid-April this year, 10,000-tailed second-generation Chinese sturgeon were released from the Rouge Garden of Yichang Riverside Park in Hubei Province to the Yangtze River. This is the 64th artificial release of Chinese sturgeon by China Three Gorges Group Co., Ltd. (hereinafter referred to as the Three Gorges Group) in more than 30 years.
The offspring of artificially bred Chinese sturgeon carry the wordless expectations from humans that they can replenish the wild population of Chinese sturgeon and bring new hope to Chinese sturgeon.
10,000 tails of the second generation of Chinese sturgeon were released from the Rouge Garden of Yichang Riverside Park in Hubei Province to the Yangtze River. Image source: Visual China
<h1 class="pgc-h-arrow-right" data-track="18" > a signal of disruption and danger to natural reproduction</h1>
The Chinese sturgeon, which was listed as a national key protected animal in 1989, is now critically endangered.
It is a migratory fish with a large body. They have lived in the Yangtze River for hundreds of millions of years, and they have formed a set of spawning and breeding mechanisms that adapt to the environment of the Yangtze River.
The Chinese sturgeon is born in the upper reaches of the Yangtze River and spends most of its life in the ocean. But when the signal of breeding starts, they will be guided by something, accurately find the mouth of the Yangtze River, travel three thousand kilometers back to their birthplace, and arrive at the Jinsha River (Yibin-Pingshan) section of the upper reaches of the Yangtze River to spawn and reproduce.
Later, the Gezhouba Water Conservancy Hub blocked the migratory breeding channel of chinese sturgeon. In order to protect the Chinese sturgeon, in 1982, the Chinese Sturgeon Research Institute was established with the approval of the Ministry of Water Resources. It is the first rare fish scientific research institution established in China due to the construction of large-scale water conservancy projects.
Dr. Jiang Wei of the Chinese Sturgeon Research Institute told reporters that the Chinese sturgeon is a flagship species, and it has a strong indicative significance. The level of resources of its population and the state of wild populations are systematic manifestations of the health status of the Yangtze River and ocean basins. "If you want to choose a species that can represent the Yangtze River ecosystem, it is the Chinese sturgeon."
In order to help the Chinese sturgeon "go home" safely, the researchers wore sonar marks, PIT marks and T-shaped marks for the Chinese sturgeon. China News Service Jing Weidong /Photo
It's hard to protect big fish; it's even harder to protect big fish whose life history is so complex. Jiang Wei said that when we first did the work of protecting the Chinese sturgeon, we were ready to fight a protracted war, and this was by no means an overnight achievement.
Now every autumn, a number of scientific research units will carry out monitoring and investigation at the spawning grounds of Chinese sturgeon under Gezhouba.
Chinese sturgeon is one of the few fish that breeds in autumn. Chinese sturgeon eggs, black, mung bean size, very sticky. They "hide" in gravel surfaces or crevices, perhaps a strategy chosen by Chinese sturgeon parents to avoid predators for their children.
Wei Qiwei told reporters that there are four main monitoring methods: hydroacoustic detection, which is used to find out the number of Chinese sturgeon parents in the investigation area; egg collection at the bottom of the river, using the bottom network of the river to collect samples for direct observation; underwater video observation, which is carried by ships with high-definition cameras to patrol the bottom of the river; and there is also a traditional way - dissecting the egg-eating fish.
Autumn monitoring in 2020 was fruitless. In fact, from 2017 to 2020, for many years in a row, the egg the size of a green bean has never appeared again.
This is indeed a red flag.
It is difficult to know the exact number of Chinese sturgeon. Researchers generally infer the condition of the population by monitoring the river section of the spawning grounds.
Wei Qiwei told reporters such a set of data: In the 1970s, the number of Chinese sturgeon breeding groups that migrated to the Yangtze River every year reached more than 2,000. Shortly after the Gezhouba interception in the 1980s, the number of breeding broodstock of Chinese sturgeon that arrive at the spawning grounds under Gezhouba each year continued to decline: from 2009 to 2012, it fell to more than 100, and after 2013, it further fell below 100, and the number of migratory groups in 2017-2019 was only about 20.
If you draw a graph, you will see a curve that falls sharply over time.
Wei Qiwei analyzed the reasons why the Chinese sturgeon population had declined to this point: the construction of Gezhou Dam blocked the migration channel of Chinese sturgeon, and they lost the spawning grounds that were once distributed in the upper reaches of GezhouBa. The stagnation effect formed by the water storage operation of many hydropower projects on the Yangtze River has increased the water temperature during the breeding season of Chinese sturgeon, which further compresses the time window for their natural reproduction. Coupled with multiple factors such as fishing, shipping and pollution, the living environment of the Chinese sturgeon has deteriorated dramatically.
Image source: Hubei Daily reporter Liu Shusong / photo
<h1 class="pgc-h-arrow-right" data-track="104" > full artificial breeding technology has been broken, and artificial breeding and stocking are controversial</h1>
Wei Qiwei's team published a paper on the extinction of the white sturgeon in early 2020. It was a larger but less publicly recognized sturgeon living in the Yangtze River.
According to their calculations, the white sturgeon was extinct between 2005 and 2010, but humans were unaware of it at that time. The fate of the white sturgeon reminds people that once the critical time node of protection is missed, it is really too late.
Fortunately, unlike the white sturgeon, the Chinese sturgeon still retains a captive breeding population.
The Chinese Sturgeon Research Institute in Yichang, Hubei Province, is now part of the Three Gorges Group and is the only institution that continues to increase and stock Chinese sturgeon.
Nearly 40 years after its establishment, the Chinese Sturgeon Research Institute has made a series of progress in the artificial breeding of Chinese sturgeon.
The breakthrough of full artificial reproduction in 2009 is a milestone progress. It means that breeding Chinese sturgeon eliminates the need to harvest wild broodstock from the wild. The offspring of those wild relatives are the descendants of the chinese sturgeon of the sub-generation; the descendants of the Chinese sturgeon who grow up in the whole artificial environment are the sub-generation Chinese sturgeon, which is also the main object of the current release of the Three Gorges Group.
The Chinese Sturgeon Research Institute also stocks up on unisexual breeding techniques for extreme cases. Today, the sex ratio of wild Chinese sturgeon populations is unbalanced. If one day in the future, only the female is left, even if it can no longer find a male partner, people can still artificially induce the activation of Chinese sturgeon eggs and produce offspring.
The researchers made a series of technical preparations. If everything is irretrievable, future generations can at least still see the Chinese sturgeon.
But the ultimate goal of artificial breeding of Chinese sturgeon is to return them to the Yangtze River and allow them to replenish their wild populations.
According to statistics, a number of institutions, including the Chinese Sturgeon Research Institute, have released more than 7 million Chinese sturgeon for more than 30 years.
Some experts who pay attention to the ecology of the Yangtze River sighed to reporters: "More than 7 million tails, so much has been released, but what about the effect? ”
Huang Zhenzhen, a professor at the China Institute of Water Resources and Hydropower Research, also bluntly said in the paper that the proliferation of Chinese sturgeon resources has "little effect".
Image source: Three Gorges Group
Doubts have always been there: Does deregulation really work? Where did the chinese sturgeon go?
After 2014, the Chinese Sturgeon Research Institute carried out the tracking of chinese sturgeon release markers. Monitoring data from 2019 shows that 73% of Chinese sturgeon released can reach the sea outlet after the release.
Jiang Wei observed that many freshwater fish swim upstream of the Yangtze River after being released. But the destination of the Chinese sturgeon is very clear - to go downstream, to the ocean. This also means that artificial breeding has not erased the instinct of Chinese sturgeon. Chinese sturgeon take 10 or even 15 years to mature sexually. So, did they follow their instincts and ever return to the Yangtze River to spawn?
This is really difficult to say. Jiang Wei said that after 2009, the scientific research and fishing of wild Chinese sturgeon has been banned. After too long a time, some short-term marks on the Chinese sturgeon are lost; the marks that can be maintained for a long time must be salvaged before they can be confirmed.
"To the extent that capacity and facilities allow, we have done a lot of basic work on the conservation category. Maybe everyone analyzes the problem differently. However, the two general directions of fish conservation are 'in situ conservation' and 'ex situ conservation', and we have been promoting this work in accordance with the thinking and framework of wild aquatic life conservation. Jiang Wei said.
In situ conservation, as the name suggests, refers to the protection of habitats and the protection of spawning grounds. One of the important measures in ex situ protection is artificial seed preservation and artificial breeding.
"The effect of the possible advancement is not so obvious to others, and there are indeed problems to be solved later." Jiang Wei said frankly, "But we have to go on and take action." As you do it, see what else you need to improve. "Not afraid of controversy. Scientific questions, while arguing, while verifying, while seeking. Chinese sturgeon conservation itself is a systematic project. "The most important thing is that we continue to form a synergy of research and conservation, and work together for this matter."
Fortunately, under the overall strategy of "Great Protection of the Yangtze River", from 2020, the Yangtze River has entered a ten-year fishing ban period. "After the fishing ban, we are still very confident in the survival ratio of Chinese sturgeon after the release." Jiang Wei stressed.
<h1 class="pgc-h-arrow-right" data-track="105" > release is more scientific, and the conservation process is in a race against the rate of extinction</h1>
The ten-year fishing ban period is a rare window period. Wei Qiwei knew that he must seize this opportunity.
The reporter asked him: "Nowadays, the Chinese sturgeon is facing many difficulties, in so many fish rescue measures, what do you want to talk about most?" ”
Wei Qiwei did not hesitate much and said bluntly: "Or release." In his view, the past release is not useless, but not enough and not standardized enough. Huang Zhenzhen also pointed out that in the past, insufficient attention was paid to the research on the effect of stocking, insufficient research on improving the survival rate of juvenile fish stocking, and serious lack of relevant basic research results, and stocking was blind.
Image source: Visual China
Wei Qiwei has conducted a detailed analysis of the release. Over the past 30 years, more than 7 million Chinese sturgeon have been released. But in the 1980s and early 1990s, small fish were released without opening their mouths. These fish are too easy to die, in fact, it is not suitable for manual release. For more than 30 years, the real "effective" stocking group is actually 1.3721 million juvenile and juvenile fish that have crossed the peak of death.
In this way, the actual average flow of Chinese sturgeon per year is less than 40,000, which is ten times or even a hundred times worse than the number of similar release specifications in foreign countries.
An example that can be used as a reference is that from 1961 to 1991, before the collapse of the Soviet Union, the Soviet Union released three major sturgeon (Russian sturgeon, flash sturgeon and European sturgeon) in rivers such as the Volga River, with annual stockpiles ranging from one million to tens of millions of fish. Later, they succeeded in restoring the natural reproduction of these fish.
Wei Qiwei calculated that according to the current amount of Chinese sturgeon that needs to be replenished, the amount of Chinese sturgeon to be released in a year should reach 3 million. "That's more than 10 million yuan of capital investment."
How to get the funds and how to make the release more scientific are all thorny problems.
Wei Qiwei believes that a sound plan for the breeding and stocking of Chinese sturgeon and resource restoration should be formulated, for example, the resource sharing and breeding utilization plan for existing seed conservation resources, the genetic management and scientific breeding matching plan based on the conservation population, the rewilding training plan for artificial breeding and stocking of Chinese sturgeon, the scientific planning and the monitoring and evaluation plan of the release effect of breeding and stocking specifications, scale and location... Moreover, it is also necessary to establish a guarantee mechanism for breeding and stocking to solve the problems of funding needs and operation management in the breeding and stocking of Chinese sturgeon.
In fact, the former Ministry of Agriculture has issued the "Chinese Sturgeon Rescue Action Plan (2015-2030)". But Wei Qiwei said that many of the ideas have not yet been truly implemented.
"The Chinese sturgeon is already in a difficult situation, and it needs people to really care and really invest." Wei Qiwei tapped his finger on the table and said almost eagerly, "The white sturgeon is extinct, and the white sturgeon is also extinct." Can't wait, the Chinese sturgeon will grow old and die, and in another ten years, they will be boiled to death. ”
If the wild population is really lost, the artificial population of the Chinese sturgeon will also degenerate.
The process of conservation must race against the speed of extinction, to act. Action can give the fate of the Chinese sturgeon a turnaround.
Chinese sturgeon cannot speak, with a drop in number, as a signal for help. Those who guard it must speak up for it.
"After studying sturgeon all my life, if you don't have it, can you still live in peace?" This fish must be preserved by me; if it is preserved, it will be a chance later! "Wei Qiwei stressed that the Chinese sturgeon rescue action plan should be implemented, especially the rescue protection and cultivation of more than 3,000 Chinese sturgeon generations, give full play to their reproductive efficiency, and implement large-scale breeding and stocking." Only in this way can the natural population of chinese sturgeon recover after 10-15 years! ”
In addition, the implementation of comprehensive conservation measures for Chinese sturgeon also includes offshore fishing control and habitat restoration, creating conditions for the protection and restoration of life in the Yangtze River and offshore waters.
Saving fish is a heavy responsibility, but also a heavy emotion.
Speaking of emotions, this expert, who has always looked solemn, finally has a smile on his face.
"It's not just me who has feelings for it, a lot of people have feelings for it." Wei Qiwei's voice softened, "This fish, you can see it can see forgetting to eat." You think that other foreign sturgeon is not as beautiful as it is. It's beautiful and mighty. ”
<h1 class="pgc-h-arrow-right" data-track="106" > related links</h1>
Chinese sturgeon: vertebrate "living fossil"
Zhang Galen
Chinese sturgeon, one of the oldest vertebrates on Earth.
Hundreds of millions of years have not left many traces on them. This shield-clad fish, which still retains the morphological characteristics of its distant ancestors, is regarded as a "living fossil".
On November 27, 2008, in Yichang, Hubei Province, I saw the newly born Chinese sturgeon "baby" in the macro lens. Courtesy of Visual China
The Chinese sturgeon is a large fish. There is a proverb among fishermen, "a thousand pounds of wax and a million pounds of elephants", "wax" refers to the Chinese sturgeon, and "elephant" refers to the white sturgeon.
Chinese sturgeon have a long lifespan, with existing observations reaching up to 40 years of age. However, it also matures late, taking about a decade. In other words, it will take a decade or more for the newborn Chinese sturgeon to bring a supplementary population to this population.
The spawning volume of Chinese sturgeon is not low, but the survival is quite limited. Traveling back to the river and returning to the birthplace of the egg is the instinct engraved in the body of the Chinese sturgeon.
It was a difficult journey, along the way, the Chinese sturgeon traveled against the current, did not eat or drink, and swam back from the sea to the place of birth. After reaching the middle and upper reaches of the Yangtze River, they will first find a place to "rest", wait for the gonads to mature, and complete the almost only mission to return to the Yangtze River in the autumn - reproduction.
Because of this life history, when the Chinese Sturgeon Research Institute did the full artificial breeding of Chinese sturgeon, everyone also played drums in their hearts.
Captive Chinese sturgeon has been kept in captivity in freshwater. Having never fought against the rapids, can they develop and mature smoothly at the arrival of "adolescence"?
Guo Baifu, the leader of the sub-generation project team at that time, once published an article saying that they had successively collected and analyzed the water environment data during the habitat and natural breeding of Chinese sturgeon in the Yangtze River and coastal areas, and summarized the technical route of regulating water temperature, water flow, nutrition and light in the pure freshwater environment to make Chinese sturgeon mature in previous years.
They found broodstock in the appropriate age echelon, used the non-invasive method of B ultrasound to distinguish the sex of broodstock, individually identified and labeled broodstock, and determined the induction scheme at the end of the stage of female gonad development to maturity. On the afternoon of October 4, 2009, the first and second generation Chinese sturgeon fry were born at the Three Gorges Base of the China Sturgeon Research Institute.
Despite the fully artificial breeding, there are still too many mysteries left to be solved in the Chinese sturgeon.
Xie Ping, a researcher at the Institute of Hydrobiology of the Chinese Academy of Sciences, once poetically compared the Yangtze River to a spectacular theater, with various species playing a common river song with their own notes and rhythms. These songs, "even if we observe and think with all our hearts, we may not be able to fully understand it."
But the special and long songs played by Chinese sturgeon and other fish should have continued to exist in the movement of the river song.
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