In Chinese waters, dugongs are functionally extinct...

This Wednesday, the British journal Royal Society Open Science published an article stating that dugongs are functionally extinct in Chinese waters . This conclusion is based on a joint study by the Chinese Academy of Sciences and the Zoological Society of London.

Dugong dugon | Pierre Vergnaud / Wikimedia Commons

The research team sorted out the last time dugongs appeared in China and confirmed that the last dugong sighting record in China was in 2008 ; a general visit to community residents in the historical distribution range of dugongs showed that local residents had not seen a dugong for an average of 23 years. According to historical data, the rapid collapse of the dugong population in China began in 1975. Combined with the changes in its habitat within its historical distribution range, the research team believes that the dugong population in Chinese waters can no longer maintain its own survival.

When there are no individuals in the remaining population that can reproduce, or the population is too small to sustain itself in the ecosystem, it is called "functional extinction". This study is about the regional functional extinction of dugongs in Chinese waters. Dugongs still exist in other places. This is not the last tragedy of dugongs.

Perhaps it is because dugongs have been out of sight for too long, or perhaps dugongs are not unique to China, that the results of this study did not cause as much discussion among the public as the functional extinction/extinction of the baiji dolphin and the white sturgeon in recent years. Like these extinction stories, the disappearance of dugongs is also made up of many regrets - irrational use of natural resources, misjudgment of the survival situation of a species, and belated protection measures ... Of course, the discussion of these regrets should not be separated from the historical background, and tracing back itself cannot have any impact on the established facts, but it can at least tell us what happened in this blue territory we are protecting, and what we should do in the future.

From "ominous signs" to organized roundups

The dugong and the Chinese have had a long history of interaction, but throughout the long history, the image of the dugong has always been shrouded in mystery.

From the Classic of Mountains and Seas to the Records of Strange Things, dugongs are described as mermaids unique to the South China Sea , whose tears can turn into pearls and whose oil can last forever. Dugongs live in warm waters, far from the core area of ​​Central Plains culture, so it is not surprising that people have such a misunderstanding. But paradoxically, in many dugong historical habitats along the coast of South China and Southeast Asia, the tradition of anthropomorphizing dugongs, especially viewing them as women in the sea, is also common. This may be directly related to their actions of holding their cubs and breastfeeding in the water, which has also become the material for the mermaid legend .

Dugongs and Sirenias are both members of the order Sirenia, but their tails are distinctly different. The dugong's tail is split into two lobes and is crescent-shaped (left); the Sirenia's tail is round (right: West Indian manatee). Although they look like whales and seals, the closest living relative of Sirenia is the elephant. | Sebastian Gerhard Venturemedia / Wikimedia Commons; US Department of the Interior, US Geological Survey

When a creature is given a mysterious color, it is likely to lead to two situations - either it is widely used because it is believed to have some special effects, or it is protected (or avoided) as a lucky (or ominous) thing. Both stories are reflected in the dugong. In coastal areas of Vietnam, Thailand, Cambodia and other places, people kill dugongs in the hope that its meat can play a "yang-enhancing" role; fortunately, Chinese dugongs seem to be the protagonists of the latter. In the eyes of fishermen in Guangdong, Guangxi and Hainan, accidentally catching dugongs in fishing nets is an ominous sign, and purposeful killing of dugongs is even rarer .

Unfortunately, the simple values ​​did not continue to this day. After the founding of New China, the elimination of feudal superstition played a positive role in most scenarios, but gradually dugongs appeared on the fishing list of fishermen. In 1955, Shou Zhenhuang, a researcher at the Institute of Zoology of the Chinese Academy of Sciences, made the first scientific record of dugongs in China based on a dugong corpse, and this dugong appeared in the seafood market in Beihai City .

A man and two dugongs killed in South Sumatra | Collectie Stichting Nationaal Museum van Wereldculturen

A larger-scale hunt began three years later. From 1958 to 1962, in order to solve the problem of food supply, Shatian Commune in Hepu County, Guangxi, organized a targeted dugong roundup operation, catching a total of 216 dugongs . The population of Shatian was not large, so many residents were able to enjoy dugong meat. Many of the elderly people in Shatian today can still recall its unique taste, which is between pork and beef.

Missed the best time for protection

Such roundups were not stopped in time. In fact, after briefly describing dugongs in 1955, researcher Shou Zhenhuang had already sensed something unusual - he learned from local fishermen that the frequency of local dugongs was far less frequent than it was decades ago. Although the fishing of dugongs has just started, the population size of this mysterious creature seems to be seriously threatened. Based on this judgment, researcher Shou Zhenhuang immediately called for the protection of dugongs by establishing a no-fishing zone.

A dugong photographed in the Red Sea | Kora27 / Wikimedia Commons

Unfortunately, Shou Zhenhuang's call was not responded to until 31 years later. Perhaps it was during these 31 years that we missed the best time to protect dugongs .

In fact, before the 1980s, whether dugongs should be protected and how to protect them were both false propositions. We did not conduct a comprehensive survey of dugongs in domestic waters, and we lacked knowledge of many details of the life cycle of this creature. In 1976, a research team led by Fudan University came to Shatin and tried to capture some dugongs for research, but the capture process was no different from the way fishermen hunted dugongs, and some dugongs died during the fishing process . Of the 26 dugongs that were eventually captured, only 3 survived, and the bodies of the remaining 23 were cut and sold to surrounding villagers as usual. The three surviving dugongs eventually died in a local reservoir, and most of the subsequent research was not completed.

To this day, the artificial breeding and reproduction of dugongs are still difficult. There are only three artificially bred dugongs in the world. This is a dugong raised in the Sydney Aquarium｜visitsealife.com

In February 1984, two dugongs were accidentally killed by a homemade fish bomb in Shatin. After being reported by the media, the incident quickly sparked heated discussions, and dugong protection finally became a hot topic for discussion among the whole nation . Two years later, a provincial dugong protection area was established with the sea area around Shatin Town as the core. In 1989, dugongs were listed as first-class protected animals. In 1992, the reserve was upgraded to a national nature reserve, and China's dugong protection work was launched.

“A dugong sanctuary without dugongs”

Establishing a dugong protection zone in Hepu is certainly a wise choice.

Among all marine mammals, dugongs are the only strict herbivores. For dugongs in East Asia and Southeast Asia, the most important food is Halodule pinifolia and Japanese eelgrass (Zostera japonica) that grow on the sandbanks on the seabed. Adult dugongs have a huge appetite, and the area of ​​seagrass that a dugong eats every day is almost equivalent to a standard football field . In order to maintain a large number of dugongs living in a certain sea area for a long time, continuous seagrass beds are essential. The water quality around Hepu is clear and stable, and the area of ​​seagrass beds in the early days of the establishment of the reserve was at least thousands of hectares . Such conditions were already quite superior along the domestic coast at that time.

Dugongs are strictly herbivorous animals. | Lord Mountbatten / Wikimedia Commons

Unfortunately, despite the repeated upgrades in the level of the reserve and the expansion of its area, dugongs are becoming increasingly hard to find. Wang Pilie, a leading figure in the study of marine mammals in China, once worriedly mentioned that the number of dugongs in the Beibu Gulf is already in a state of "dramatic decline", and in the survey report at the beginning of the operation of the reserve, no traces of dugongs were found at all .

In 2000, Nanjing Normal University organized three consecutive surveys in the Hepu Nature Reserve. Although no traces of dugongs were found, the root of the problem was found. Unlike the "seagrass patches" and "seagrass that could lift people up" recalled by residents, the seagrass beds in Hepu had already been seriously degraded , and within the core area of ​​the reserve, continuous trawlers and sewage discharges were still seen everywhere.

Dugong feeding tracks in the seagrass fields of Okinawa｜teamzan.ti-da.net

This is actually the embarrassment faced by the Hepu Nature Reserve. Since the provincial nature reserve was established in 1986, the Hepu Nature Reserve has not had a corresponding management agency for 11 years. After the Hepu Dugong National Nature Reserve Management Station was established in 1998, the limited manpower could not effectively control all areas of the reserve, and was often passive in the struggle with local departments over " development or protection ".

In 2010, there were still 254 hectares of seagrass beds in the reserve, but the following year, construction of Shatin Port began, and sand pumping during the construction affected the transparency of the seawater, and the area of ​​the seagrass beds quickly shrank to 13 hectares. For many years thereafter, local residents carried out marine aquaculture in the reserve and used high-pressure water guns to wash away the silt on the mudflats in search of starfish. In 2014, the port dredging project was carried out directly in the core area, and the area of ​​the seagrass beds reached a historical low of 0.5 hectares that year . In the great environmental changes, the once dominant algae, Diptera: sphenops sphenops and Japanese eelgrass, have completely disappeared. Hepu can no longer support even a dugong.

Toxoplasma siphonaptera jelly｜SoHome Jacaranda Lilau / Wikimedia Commons

As one of the three major marine ecosystems, along with mangroves and coral reefs, the ecological role of seagrass beds has been neglected . However, they are extremely fragile. An abnormal storm surge that causes turbid seawater and abnormal offshore salinity caused by abnormal land precipitation can lead to serious degradation of seagrass beds. Moreover, seagrass beds are also under pressure from seawater pollution and direct encroachment caused by human activities.

From my country's Bohai Sea to the South China Sea, most of the once thriving seagrass beds have disappeared, which has directly affected the survival of many organisms that rely heavily on seagrass beds. In Rongcheng City, Weihai, Shandong, the degradation of seagrass beds once caused the whooper swans to abandon this vital wintering place; in Jiaozhou Bay, Qingdao, the decline of seagrass beds not only made the "seagrass houses" that the locals were proud of unsustainable, but also directly affected the scale of fish breeding. Against this backdrop, the decline of the strictly vegetarian dugong was not an unexpected outcome.

The IUCN Red List classifies dugongs as vulnerable and considers their numbers to be declining | IUCN

In a media interview last year, the managers of the Hepu Nature Reserve admitted that they have always been unable to let go of the reputation of "a dugong reserve without dugongs". Fortunately, today's Hepu is not sad because of the "foregone conclusion". China's seagrass bed restoration work is underway here and in other parts of China . The seagrass bed restoration work in Rongcheng, Shandong, led by the Ocean University of China, has restored nearly 400 hectares of Japanese eelgrass beds. Today, Rongcheng Swan Lake has regained its former prosperity.

Rongcheng Swan Lake seagrass bed restoration site | China Daily

In comparison, as the largest seagrass bed distribution area in China, the road to Hepu may be longer and more difficult. But as long as we keep moving in this direction, letting the dugong return home may not just be an empty idea.

Dugongs are still distributed in other sea areas. If my country's coastal habitats can be restored, through artificial introduction or dugongs' own migration, my country's dugong population may still be able to recover. We look forward to the arrival of this day｜Vardhanjp / Wikimedia Commons

References

[1] Lin Mingli, Turvey Samuel T., Han Chouting, Huang Xiaoyu, Mazaris Antonios D., Liu Mingming, Ma Heidi, Yang Zixin, Tang Xiaoming and Li Songhai.2022. Functional extinction of dugongs in ChinaR. Soc. open sci.9211994211994http://doi.org/10.1098/rsos.211994

[2] “Dugong Sanctuary without Dugongs”, https://mini.caixin.com/2021-11-02/101794833.html?cxapp_link=true

[3] “Report on the Damage to Mineral Resources Caused by Illegal Mining of Quartz Sand Mine in Shatian Port Appraisal Area, Hepu County, Beihai City”

[4] “Asset Appraisal Report on the Market Value of Sea Sand and Yellow Sand, Quartz Sand and Tailings after Processing at Shatin Wharf in the Intended Judicial Disposal Commissioned by the People’s Court of Yinhai District, Beihai City”

[5] Chen Xueping. 2019. Analysis of the environmental governance model of Hepu Shatian Port from the perspective of multi-center governance.

Author: A man is wandering

Editor: Mai Mai

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