In March this year, a marine creature - the Chinese white dolphin - appeared in the waters of the Xijiang River in Wuzhou, Guangxi Province, 400 kilometers from the mouth of the Pearl River!
After individual identification, it was learned that it was the same as the white dolphin that had mistakenly entered the Foshan and Zhaoqing river basins of Guangdong Province many times before! During the last search and rescue operation, a large area of brownish-yellow patches could be clearly seen on the back of the white dolphin, which was caused by a skin infection, and the situation was very critical! Unfortunately, after many efforts, it was still unable to help it return to the sea alive[1].
Source: The Paper
This is not the first time that Chinese white dolphins have been found in freshwater waters! In the recent November 2020 alone, a lost white dolphin was found in the Huizhou section of the Dongjiang River in Guangdong Province; at the end of 2020, an elderly white dolphin also lost its way into the Shakou Water Conservancy Hub Station in Foshan, Guangdong Province...
These rare Chinese white dolphins, which originally lived in the ocean and were listed as China's national first-class protected animals, have run to the wrong places so often in recent years:
Or swim frequently into freshwater rivers
Either stranded on shore
Either it will be photographed by more and more tourists
Is their number restored, or is there no land gone?
01 The crisis of the first-class baby white dolphin
According to Thomas A. Jefferson's 2016 estimates, the global population of Chinese white dolphins is only about 5,700, and it is still decreasing.[8]! Currently, the Chinese white dolphin is familiar with the giant pandas, pangolins and Siberian tigers (yes!). Guandashan No. 1, which broke into a village in Heilongjiang some time ago, is one of them) belongs to the same level of protection; it is also a vulnerable species (VU) with the Ku's Stone (pictured below) and the giant panda with only more than 1,800 animals.
Note: a. The pink block area in the map is the global distribution zone of the Chinese white dolphin
b. The "red, orange, yellow, green, blue, purple, black, light blue, gray" icons in the map represent the main habitats and populations of 10 Chinese white dolphins in the world, including the East Taiwan Strait (China), Xiamen Bay (China), Pearl River Estuary/Hong Kong (China), Leizhou Bay (China), Beibu Bay Shatin (China), Sam Niang Bay (China), Kuching, Malaysia, Surat Thani Province, Thailand, Khanom Thailand, and Bengal Bay
Chinese white dolphin (scientific name: Sousa chinensis), also known as Mazu fish, Indo-Pacific camel dolphin, is mainly distributed in the southeast coast of China, through southeast Asian waters to the northeast coast of India (above), living in the brackish waters of the estuary or in the shallow sea near the shores. In this distribution belt across the Pacific and Indian Oceans, the population distribution of white dolphins is not continuous, and different populations are scattered in various estuaries and their offshore areas.[8] However, according to research by Wang Xianyan et al. (2012), chinese white dolphins have historically had large populations of continuous distribution in Chinese waters[14].
This image is adapted from Bingyao Chen et al. (2018), since the original literature mainly studied the pigmentation patterns of the Chinese white dolphin populations in Xiamen, Shatian-Caotan and Sanniangwan, the habitat patches of the above three populations were green marked. The red and green patches after adaptation are not particularly distinguished in this figure, and both represent the habitat distribution of the Chinese white dolphin population in China
Among the habitats that have been discovered in China, since most of the existing systematic scientific research on Chinese white dolphins is mainly concentrated in the Hong Kong population (in recent years, it has also been studied in various estuarine areas such as Chinese mainland and Taiwan), before the study of Thomas A. Jefferson (2016), there were few studies of newly discovered Chinese white dolphins in the southwest waters of Hainan Island (hereinafter referred to as Sanya Sea Areas), and some scholars have based on the experience of "Chinese white dolphins do not live in areas with pure marine environment" [16] It is believed that the "white dolphins" found in sanya are different species, so some literature does not count the population of Chinese white dolphins in this area.
However, a 2016 field study by Li Songhai's team, a researcher at the Institute of Deep-Sea Sciences and Engineering of the Chinese Academy of Sciences[17], showed that the presence of Chinese white dolphins in groups was observed several times in areas with a water depth of less than 20 m in Sanya, while the World Conservation Union (IUCN), Bingyao Chen et al. (2018) and other related studies and literature (as shown in the above figure), there are also sub-populations of Chinese white dolphins.
Populations of Chinese white dolphins photographed off the coast of Sanya
图源: Songhai Li et al (2016)
The Chinese white dolphin was listed as a national protected animal in 1989 and listed on the IUCN Red List of Threatened Species in 2008, and they have been well protected accordingly, but their numbers continue to decline. Among them, the largest population of Chinese white dolphins (2637 heads) is decreasing at a rate of 2.5% per year, and at this rate, more than half of the individuals will disappear in the next 50 years[18], while other smaller populations will also face a higher risk of extinction.
Seeing these shocking numbers, you may be curious, take protective measures are not top? What is causing such a serious crisis of Chinese white dolphins?
02 The circle of life and circle of friends is getting narrower and narrower
Dr. Zheng Ruiqiang, an expert in cetacean porpoise research, said that habitat decay (reclamation, coastal construction, marine engineering, etc. lead to habitat reduction), human activity disturbance (land-based pollution, overfishing, abandoned fishing gear, marine noise, etc.) and population isolation are the three main threat factors affecting the survival of Chinese white dolphins.
Habitat decay is a major threat factor for the near-shore Chinese white dolphin. With the rapid development of China's marine economy, the underwater noise and suspended sludge generated by the construction of reclamation, coastal construction, marine engineering and other projects not only seriously affect the daily foraging, habitat, mating and other activities of white dolphins, but also indirectly affect the food source of white dolphins because they affect the activities of fish. Environmental pollution and reclamation projects are more likely to cause the decline and fragmentation of white dolphin habitats, which in turn affects genetic exchange between populations.
Human disturbances also pose a huge threat to the survival of white dolphins. For example, overfishing causes the number of white dolphins to reduce their food sources, and even leads to white dolphins and humans grabbing fish to eat, so desperate to make some white dolphins leave shocking marks on their bodies - they are scratched by boats or propellers when preying; fishing garbage and discarded fishing gear will also cause white dolphins to be entangled; not only that, because the white dolphins at the top of the food chain have a strong ability to enrich harmful substances such as heavy metals and organic pollutants. These harmful substances that impair the physical function of living organisms are enriched in white dolphins through the food chain, and the content of harmful substances in white dolphins is much higher than that of other fish.
Population isolation is currently the biggest challenge for Chinese white dolphin populations. At present, the habitat of Chinese white dolphins in China is seriously fragmented, and many populations are aging due to age composition, resulting in increasingly irrational population structure. The populations of white dolphins in the Pearl River Estuary and Xiamen may have genetically differentiated, while the Shantou white dolphin population currently forages 90% of the time (the normal foraging time of white dolphins is generally 60%), and the fertility rate is extremely low.
Taking the small population of Chinese white dolphins (13 heads) in the waters of eastern Guangdong (Shantou) as an example, in 2008, a female dolphin named "Uncle Liang" gave birth to a small white dolphin "Fuxing", which represented the hope of a population of white dolphins, which survived in this world for less than a week and died; and in the past 10 years, all newborn individuals (3 heads) including "Fuxing" have not been spared. For most mammals, the population drops to this number, and there is only one fate that awaits them–the extinction of the population.
"Uncle Liang" (left) and its dying child "Fuxing"
03 Protection measures are a drop in the bucket, and you and I need to participate together
The state has always attached great importance to the conservation of Chinese white dolphins, and has made efforts to improve laws, establish protected areas, and improve public awareness of conservation, so as to build a safe home for Chinese white dolphins as much as possible.
However, according to the IUCN's assessment, the number of Chinese white dolphins has been declining in recent years [8]. It is also a reminder that the current protection measures we have taken against white dolphins are not enough. For example, the existing Chinese White Dolphin Sanctuary in China, although it protects part of the habitat of Chinese white dolphins and reduces the interference of human activities, it cannot completely cover its main habitat. At the same time, the country's effective control of land-based pollution in recent years has reduced the impact of marine pollutants on white dolphins, but there is still a long way to go in terms of controlling marine plastics and discarded fishing gear. In addition, how to carry out scientific planning and effective supervision of inshore aquaculture and fishing activities will also directly affect the habitat quality of white dolphins.
The conservation of Chinese white dolphins focuses on the continuation of the population and the harmonious coexistence with the living environment, if only the number of individual white dolphins and the "personal" safety of white dolphins in a certain area are not improved, without improving the overall living environment such as water quality, habitat environment, food sources, etc., white dolphins still face huge survival challenges. To solve these systemic problems, it is necessary for the whole society to participate together, and people need to form awareness and action to protect white dolphins.
04 White Dolphins and Marine Culture
From the petroglyphs of human ancestors recording production and life to the Chinese characters evolved from biological images, the creatures that accompany human activities have always served as a link between nature and culture. As the flagship species of inshore, the white dolphin is also a link in the fisheries culture of coastal residents and is an integral part of collective memory. In the southeast coastal areas such as Fujian, Guangdong and Taiwan, people use folk activities, oral stories, etc., to honor the white dolphin as "Mazu fish" (in the Mazu culture of Fujian, Guangdong and Taiwan, every Year in March 23 Mazu Birthday, people have to carry out sacrifice activities, legend says that when they face the sea to worship Mazu, they often see white dolphins in the sea and jump out of the water. In that ancient era, people thought that the white dolphin was Mazu's mount, so they honored the white dolphin as "Mazu Fish", enshrined as a sacred beast for good luck, and coexisted in harmony with the white dolphin, until today.
The "Mazu Fish" painting of the Tianhou Temple in Quanzhou
Chinese white dolphins are still a sedentary species, where they are born and have been aging there. For millions of years, white dolphins have been active, preying, participating in the material cycle of marine ecosystems in estuaries and shallow coasts where human production and life highly coincide with human production and life, and have never left. Human activities directly affect their survival, and their living conditions also directly reflect the health of the marine environment and have an indicative effect on estuaries and marine ecosystems. These are closely related to our living environment.
To protect the Chinese white dolphin is to protect ourselves, "only if the white dolphin is alive and well, we will fish every year."
Resources
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