On May 23, 2019, local time, in Trang Province, Thailand, a dugong named Marim was under the care of staff and veterinarians at the Phuket Marine Life Center. The researchers hope that after a period of artificial feeding, Marim will learn to live independently and return to the ocean. (Visual China/Photo)
Centuries ago, at dusk or dawn, sailors often saw some "beautiful women" floating on the surface through the mist of water in the sea, and some even held their babies to their chests to breastfeed, which is the origin of the legendary "mermaid". The romantic mermaid is based on the dugong, the only herbivorous mammal in the ocean.
A paper published in the Royal Society Open Science (2020 impact factor of 2.963) on August 24, 2022, points out that dugongs have experienced rapid population declines in recent decades and are now functionally extinct in China. The paper was co-authored by 10 authors from the Institute of Deep-Sea Sciences and Engineering of the Chinese Academy of Sciences and the Zoological Society of London.
From white sturgeon to white sturgeon dolphins, the biological term "functional extinction" has become widely known, which refers to the decline of a population of a certain organism or a certain type of organism under natural conditions to a state where it is impossible to maintain reproduction. After research, scientific institutions or scholars have the right to make a judgment on the functional extinction of a species.
Dugongs inhabit the coastal waters of more than thirty tropical and subtropical countries. Helene Marsh, an Australian dugong expert and professor at James Cook University, replied in an email to Southern Weekend that the number of dugongs worldwide has fallen by more than 30 percent in the past 75 years.
In the IUCN Red List of Threatened Species, dugongs are protected on a "vulnerable" scale. The IUCN considers dugongs to be regionally extinct in Mauritius and Taiwan Province of China and in a "critically endangered" state in Japan. The IUCN Red List of Threatened Species has been established and operated for more than seven decades and is an authoritative indicator of international biodiversity.
In China, dugongs are nationally protected animals. There are also legends about dugongs in ancient mainland China, and in the South China Sea it is known as the "Fish People". But in recent years, the dugong has rarely appeared in mainland waters, and because it is not often seen, even its name is slightly unfamiliar to the public.
The paper shows that man-made fishing and habitat seagrass bed degradation have combined to lead to a rapid decline in The Dugong population in China. While China's waters are home to about a third of the world's marine mammals, and some other species are in decline, there is an urgent need to optimize marine conservation efforts.
"It was possible to claim the functional extinction of dugongs, but it was never said"
The only time Xu Xinrong, a cetacean expert, saw a dugong was in 2000 near a coral reef 250 meters off the coast of Gangmen Village in Dongfang City, Hainan Province. "The water is shallow and there are basically no fishermen."
Xu Xinrong, a senior engineer at the School of Life Sciences at Nanjing Normal University, surveyed dugongs in the coastal waters of Guangdong, Hainan and Guangxi from September to November 2000.
Xu Xinrong told the Southern Weekend reporter that the dugong diving time is long, the water time is short, the temperament is timid and sensitive, and the fishermen are not easy to find when working. He saw a small group of 5 dugongs, about 70 meters from the boat, and could only see a few rough outlines slowly floating out of the water for ventilation, and the action of exiting the water was different from that of dolphins, sinking in less than 5 seconds. Interval about 10 minutes, out of the water again to breathe. But as the research vessels prepared to approach the photographs, they disappeared in the mirror-like calm sea.
According to a paper jointly released by the Chinese Academy of Sciences and the Zoological Society of London, from July to August 2019, four researchers with knowledge of marine mammals traveled to Hainan, Guangxi, Guangdong and Fujian, together with 21 volunteers, to visit 66 villages in 22 cities, covering all known dugong ranges in Chinese mainland waters.
The researchers interviewed 788 fishermen with an average age of 51 years and an average of 25 years of fishing. According to the survey, only 5% of people have ever seen a dugong in person, and the average last sighting date is 23.2 years ago. In the past 5 years, only 3 fishermen have seen dugongs.
The researchers combed through the historical record and found that the number of dugongs in China peaked around 1960, declined rapidly from 1975, and has not been witnessed since 2008. The research team believes that dugongs have become functionally extinct in China.
"I agree with the conclusions of the article, but I think there are flaws in the article's approach to investigation." Xu Xinrong said that the author of the paper only distributed questionnaires to fishermen, but he did not see detailed data on the survey and enough effort to go to sea. Going out to sea to investigate can not only use the naked eye and sonar technology to observe dugongs, but also understand the scale of dugong food seagrass and determine whether it can "feed dugongs".
In this regard, Helen Marsh believes that fishermen work on the water every day and are often good observers. "Looking for low-density dugongs in Chinese waters, using air or vessel surveys is like finding a needle in a haystack." Helen Marsh wrote in an interview email to Southern Weekend reporters.
"In fact, we can already claim the functional extinction of dugongs, but we have never said it." Xu Xinrong said that in addition to data support for wildlife surveys, there must also be a certain amount of work effort, such as research that lasts for a long time. The greater the amount of effort, the more convincing the conclusion.
Xu Xinrong has studied dugongs for more than a decade, and in the 2000 survey he and his colleagues went to sea 36 times and withdrew 203 interview questionnaires from people in different occupations, but still believed that the amount of work he had done was not enough, and he did not have a clear grasp of some data such as the size of seagrass in the subtidal zone (the underwater shore slope outside the intertidal shoal).
This is also why Xu Xinrong has repeatedly emphasized the view of recognizing the functional extinction of dugongs, but believes that there is still room for improvement in the method of investigation in the article. The author of the paper politely declined the southern weekend reporter's request for an interview.
"No one wants to see a dead individual for the first time"
Since Xu Xinrong saw and recorded the dugong in 2000, there have been few public observations of dugongs in China for several years, and the most recent recorded witness occurred in 2008, when Wang Lijun, a professor at the School of Life Sciences of Hainan Normal University, identified this strange fish known locally as "pig head fish" on the spot.
One night in the early summer of 2008, a dead "pig's head fish" drifted to the coconut grove in the eastern suburbs of Wenchang City, Hainan Province, with a fish whose mouth resembled a pig's and whose upper lip was covered with a hard "beard", and no one in the local area recognized what kind of fish it was.
Wang Lijun recalled to the Southern Weekend reporter that when he arrived at the scene, it was only a dozen hours after the death of the "pig's head fish", and its nostrils were even flowing fresh red blood, without any peculiar smell. To the touch, the dugong's skin is not as smooth and somewhat rough as that of cetaceans.
After identification, the "pig's head fish" is a dugong, 2.6 meters long and weighs about 800 pounds. After consultation with the competent authorities, the College of Life Sciences of Hainan Normal University used a car to pull it back to the school, and after dissection, it was found that the right side of its body was seriously damaged, 3 ribs were broken, and there was a large area of congestion and tissue injurious necrosis under the skin, while the left side of the body was less damaged. There were a large number of motorized boats in the nearby port, and Wang Lijun deduced that the collision of the ships was the direct cause of the dugong's death.
"It's a pity that dugongs haven't been seen for years, and no one wants to see a dead individual for the first time." Wang Lijun said. Later, the dugong was made into a specimen and stored in the Hainan Biodiversity Science and Technology Museum.
Wang Lijun said that boats and propellers are "killers" of large animals such as dugongs and cetaceans. A 2006 paper found that 7 per cent of dugong deaths off the coast of Queensland, Australia alone were due to ship collisions.
In addition to ship collisions, dugongs face multiple human threats, such as overhunting.
Wang Pilie, a researcher at the Liaoning Academy of Marine and Fishery Sciences, who has been researching marine mammals for more than 50 years, published an article in 2007 saying that the biggest threat to dugong resources in the Beibu Gulf came from mass killings in the late 1950s and early 1960s. According to the former Fisheries Bureau of Guangxi Zhuang Autonomous Region, 58 were hunted during the five years from 1958 to 1962, and 30 were killed along the western coast of Hainan Island during the same period, "giving devastating damage to dugong resources." From 1975 to 1976, 28 animals were killed in the Hepu waters, "which further made the dugong resources tend to extinction and it was difficult to recover."
According to Wang Lijun, the main purpose of hunting dugong is to eat meat and use its subcutaneous fat to refine oil.
The dugong's "relative", the giant dugong (also known as the Stella manatee), was eaten by humans until it became extinct. The giant dugong belongs to the same family as the dugong of the order Manatee, and after the giant dugong was discovered in the Bering Strait in 1741, it became extinct in 1768 due to extensive human hunting. Today, only the dugong is left as the "only seedling".
Habitat seagrass beds are destroyed
Not only does overfishing threaten dugong populations, but inshore human activities also destroy dugong habitats.
Dugongs feed on aquatic plants such as seagrass and seaweed, and an adult dugong can eat at least 40 kilograms of seagrass per day. Dugongs often inhabit shallow waters near the seagrass bed, which coincide with areas of human activity.
Zhao Peng, an associate researcher at the State Key Laboratory of Marine Resource Utilization in the South China Sea at Hainan University, who has long been engaged in seagrass ecology research, told Southern Weekend that reclamation, fishing activities and water pollution are the main causes of the destruction of seagrass beds. For example, fishermen's activities such as snail digging and sandworm digging cause seagrass beds to break and patch; When the bottom trawler operates, almost the entire seagrass is uprooted; Eutrophication of water bodies can cause large outbreaks of algae, which compete with seagrass and lead to the degradation of seagrass beds.
Established in 1986, Guangxi Hepu Dugong National Nature Reserve is one of the typical examples of dugong habitat destruction. Zhang Hongke, director of the Hepu Dugong Nature Reserve Management Center, wrote in 2013 that since the end of the 1980s, the local governments around the reserve have vigorously developed marine resources, coupled with the devastating damage to the ecosystem caused by fishing activities around the reserve, and the damage to the seagrass ecosystem is serious.
According to a 2020 survey by Lin Jinlan and others at the Guangxi Zhuang Autonomous Region Institute of Oceanography, seagrass area has been shrinking as a whole since the establishment of the reserve, and the area in 2017 is less than one-third of what it was in 1987.
Zhao Peng pointed out that the seagrass in Guangxi shows patchy characteristics, and the seagrass bed situation in some parts of Hainan is not optimistic at present. More importantly, the seagrass bed, along with mangroves and coral reefs, is called the three typical marine ecosystems, but the study of seagrass beds started late in China, the legal status of seagrass is still relatively vague, and conservation and management measures need to be strengthened urgently. At present, the number of seagrass bottoms on the mainland is still unclear, and seagrass research still needs to be further enhanced, and it is necessary to strengthen the construction and continuous monitoring of seagrass bed protection area system.
The good news is that parts of the continent have now begun to repair seagrass beds. In Zhao Peng's view, protecting the seagrass bed and protecting the habitat of dugongs is more important than strengthening the management of human activities in addition to restoration. Seagrass beds are very susceptible to human influences, and even tourists rushing to the sea will pose a threat to it - in addition to directly destroying the seagrass bed, it will also cause sediment to re-levitate, affecting seagrass photosynthesis and causing seagrass degradation.
"To date, there have been few effective management measures to reduce the impact of humans on dugongs." Helen Marsh is pessimistic, "Most dugong sanctuaries outside of Australia are 'paper parks' with laws and regulations but poor implementation. She believes that the most urgent thing is to solve the livelihood problems of local residents in protected areas and provide alternative incentives for residents to protect dugongs.
On May 18, 2021, staff from the Institute of Marine Ecology of the Hainan Academy of Oceanography and Fisheries Sciences inspect the growth of seagrass beds in the waters from Qinglan Port to Gaolong Bay in Wenchang City, Hainan Province. (Visual China/Photo)
Reintroduction, the challenge is not small
Although functional extinction is a precursor to actual extinction, it does not mean that species will eventually lead to formal extinction. If rescued, there is still a glimmer of hope of redemption, the most famous example is the crested ibis, and other cases include European bison, Asiatic lion and so on.
In June 2022, the China Biodiversity Conservation and Green Development Foundation (hereinafter referred to as the China Green Development Council) established a dugong research group to reintroduce it to China by restoring the entire ecosystem on which dugongs depend. The predecessor of the China Green Development Council was the China Elk Foundation, which reintroduced elk from the UK to China.
"We're not buying dugongs and putting them in the sea, as some zoos do." Zhou Jinfeng, secretary general of the China Green Development Council and head of the dugong research group, told Southern Weekend reporters that the dugong should be reintroduced to restore its habitat.
Zhou Jinfeng introduced that including dugongs, the core of protecting all biodiversity is similar and can be summarized into a trilogy: the first step is "protection", that is, the maintenance of the natural environment and the reduction of the interference of human activities on the marine environment; The second step is "restoration", which can be restored naturally by delineating marine protected areas, re-rewilding, etc.; The third step is "conservation", which is to conduct targeted scientific research on coastal organisms and use scientific means to enable organisms to reproduce naturally.
It is imperative to rebuild the dugong habitat offshore, including planting seagrass beds, setting up nature reserves, and re-establishing ocean connectivity, hoping to use natural methods to allow dugong populations to return to China's coastal waters through migration. The reintroduction of the species can also be considered in the future. "Judging from the model we have proposed, there is no precedent for successful reintroduction of marine animals." Zhou Jinfeng said.
However, even if habitats are restored and all threats are eliminated, the reintroduction of dugongs to China will still face significant challenges.
"On the one hand, where did the dugong come from?" Helen Marsh said that although there is only one kind of dugong, it also shows genetic diversity, so ideally, dugongs need to come from a country with a rich genetically diverse population, and the dugong population in Australia still has a relatively rich genetic diversity, but preliminary studies have shown that the genetic diversity of dugongs in other countries is not ideal.
On the other hand, there has never been a successful case of dugongs rewilding from captivity. "Every dugong stays with its mother for years to learn how to adapt to the habitat." Helen Marsh says dugongs are long-lived, slow-breeding animals and that it may be necessary to protect dugongs in a very large fenced sea and provide abundant seagrasses so that they can adapt to their habitats without any threats.
Southern Weekend reporter Lin Fangzhou