What are the implications of the extinction of the Yangtze River white sturgeon? Source: Xining Evening News

What are the implications of the extinction of the Yangtze River white sturgeon?

　　On the second and third day of the new year, the news of the "extinction of the white sturgeon" hung on the hot search list, and hundreds of millions of readers saw that people paid attention to it.

　　But in the eyes of experts, such attention is a bit late.

　　The king of freshwater fish in China

　　White sturgeon is one of the very few ancient fish that survived from the Mesozoic Cretaceous Period 150 million years ago, with an extremely narrow distribution, which is only found in China in the world, and is also known as the "Yangtze River White Sturgeon". Mainly concentrated in the Yangtze River Basin, known as "living fossils in the Yangtze River", it has great academic research value and belongs to China's first-class protected wild animals. The white sturgeon's snout is half as long as its body, also known as the "elephant fish", and is the first "giant" in the freshwater fish family, with a length of up to 7 meters, a weight of more than 700 kilograms, and its lifespan is generally about 30 years.

　　The white sturgeon has a distinct feature: the head is long, accounting for 1/3 of the body length, the small individual accounts for about 1/2 of the body length, and the cloth has a plum-shaped sensory device - trap. The snout is elongated and sword-shaped, with a pair of short whiskers on its ventral mask. The eyes are very small. The mouth is large, lower, curved, and has fine teeth on the upper and lower jaws. The gill foramen are large and the posterior margin of the gill membrane is pointed. The surface of the body is smooth and scaleless. It inhabits the lower middle and lower layers of rivers , sometimes entering large lakes. White sturgeon is a large ancient fish in the Yangtze River that is only second to the Chinese sturgeon, up to two or three meters long, due to the deterioration of the ecological environment, the distribution area of the white sturgeon has gradually shrunk, the number has decreased year by year, and the individuals have become smaller and smaller. White sturgeon is a typical carnivorous fish, and its food includes fish, shrimp and crabs.

　　Sichuan fishermen have a saying that "a thousand pounds of wax, ten thousand pounds of elephants". "Elephant" refers to the Yangtze River white sturgeon, which is said to grow up to tens of thousands of pounds. The white sturgeon is large and fast swimming, known as the "tiger in the water", "the king of Freshwater Fish in China", and it is also one of the ten largest freshwater fish in the world.

　　In addition to the white sturgeon, another 140 species of fish were also missing in the most recent survey, although the interval between the two surveys was 41 years. The vast majority of them are endangered species.

　　The white sturgeon and the Yangtze river anchovy were declared functionally extinct in the wild, and the white sturgeon was declared extinct.

　　The IUCN official microblog released a message at 12:31 on January 3 that iucn has not officially announced the extinction of the white sturgeon. In this regard, Dr. Wei Qiwei, chief scientist and researcher of the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences, replied to reporters on the afternoon of the 3rd, "It was not officially announced, but the evaluation has been completed." Whether it is published or not does not affect its scientific conclusions. According to the official website of the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences, since 1996, Wei Qiwei has been a member of the IUCN Species Survival Committee (IUCN/SSC) Sturgeon Expert Group.

　　In 2007, Wang Ding, a researcher at the Institute of Hydrobiology of the Chinese Academy of Sciences, wrote an article reflecting on why the baiji dolphin became extinct, mentioning that the habitat was fragmented and even lost; food was scarce and damaged by human electric bombing.

　　What reflection can the extinction of the white sturgeon bring to people?

　　The research paper published online on December 23, 2019 by the international academic journal Holistic Environmental Science provides some enlightenment.

　　In this paper, factors such as habitat fragmentation, degradation, and obstruction of egg-laying migration are re-mentioned.

　　The researchers wrote in the paper that the development of the Yangtze River and dam construction in the 1970s further reduced the number of individuals in the white sturgeon at that time. As a large carnivorous fish and top predator in freshwater, the population of the Yangtze River white sturgeon may never have increased. Overfishing may have exacerbated its extinction. Habitat degradation is also one of the key causes of the extinction of the Yangtze River white sturgeon.

　　The corresponding author of the paper is Dr. Wei Qiwei, and the first author of the paper is Dr. Zhang Hui.

　　According to the paper, the extinction of the Yangtze River white sturgeon is caused by multiple threats, and the protection of endangered species in the Yangtze River Basin urgently needs to be improved in order to avoid more similar extinction events.

　　The paper said that from the extinction event of the Yangtze River white sturgeon, there are many lessons to be learned. The paper mentions three of them.

　　First, studies have shown that the key point in time to save the Yangtze River white sturgeon was before 1993 (i.e., before its functional extinction) and at the latest before 2005 (i.e., the projected time of extinction). But all the substantive rescue efforts, such as aquatic exploration, experimental capture surveys at their historic spawning grounds, and artificial reproductive technology studies, were carried out after 2006, and "it was too late to stop their extinction.". For some species, the window of conservation opportunity may have closed. But for other species that are "still alive" and still have individuals alive, it is important to seize the remaining opportunities. The researchers believe that the extinction risk of all endangered species in the Yangtze River should be assessed as soon as possible to determine their conservation measures and priorities, so as to avoid possible further extinction events.

　　Second, the urgency of prioritizing the conservation of species at greatest risk of extinction is so urgent. Conservation should focus on species that have not been seen for many years or have suffered severe habitat loss and rapid population decline. For example, luciobrama macrocephalus (long-billed eel) and Sichuan white turtle (onychostoma angustistomata) have not been found for many years, but have never even been evaluated on the iUCN Red Species List. In addition, some species, such as cochineal, round-mouthed copperfish, Sichuan Zheluo salmon, Chinese sturgeon, Yangtze River sturgeon, etc., although evaluated, have not seen natural reproduction for many years.

　　Third, new comprehensive surveys of the entire Yangtze River basin are needed and institutionalized on a regular basis, for example, every five years. The paper said that the Yangtze River Basin was conducted for the first comprehensive scientific survey in 1973-1975, and the second comprehensive survey was conducted 41 years later, in 2017-2018. Due to the lack of sustained records, it is currently impossible to determine the fate of the 140 "disappearing" species in the second survey, such as whether they are extinct. As a result, it is not possible to intervene in a timely and effective manner.

　　On January 3, a doctoral student at the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences told reporters that the ultimate significance of protecting a species lies in protecting its habitat and preserving the complete natural ecology and the organisms in it.

　　The doctoral student said that if a species wants to survive, it must have food, shelter, egg laying grounds, and it must survive; it must also have surviving individuals, who must be able to grow, mature, have the ability to reproduce, and maintain a certain population. In the context of conservation, the purpose of any wild animal release is population reconstruction. But the premise of release is to survive in the wild.

　　The Yangtze River white sturgeon was the most sighted in 1985

　　The long-nosed Yangtze River white sturgeon also has five brothers. But four of them, people have only seen in fossils. Of the remaining two species, in addition to the Yangtze River white sturgeon, its only remaining brother is the small american spoon sturgeon living in the Mississippi River in the United States. Their long noses are called spoon-snouts, like the long handles of a tablespoon.

　　According to the above paper, from 1981 to 2003, people saw the Yangtze River white sturgeon 210 times, and only 45 times were recorded in detail: body length, sighting location, fish age, etc.

　　The vast majority of yangtze river white sturgeon sightings occurred before 1995, with the most common around 1985. Although China had previously banned the fishing of Yangtze River white sturgeon in 1983, bycatch was frequent.

　　Of the more than 200 Yangtze River white sturgeon sightings, 47 occurred in the upstream section and 159 in the downstream section, accounting for 75.7% of the latter.

　　Based on the only monitoring records, researchers believe that the white sturgeon that appeared in the Yangtze River during the dinosaur era was extinct as early as 2005 and as late as 2010. "The loss of this large representative species, which is unique and attractive in freshwater ecosystems, is a sad and irreparable loss." They wrote in the paper.

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