Dugongs, a species of sea cow that roam the ocean floor in Asia and Africa and are believed to inspire ancient legends about mermaids, have been discovered off the southern coast of China. Kingdom for many centuries.
However, not recently. The dugongs have become the first functionally extinct large vertebrates in China’s coastal waters, a new study shows, the result of a rapid population decline that began in the mid-1970s. .
“Functional extinction” means that even if some dugongs are still alive off the coast of China, their numbers are too small to sustain a viable population. Manatees are sometimes entangled in fishing nets, and the seagrass they feed on in the northern parts of the South China Sea has been degraded over the years.
Research in the journal Royal Society Open Science, based on interviews with nearly 800 fishermen in southern China and published online this weekis a cautionary tale for other mammals in East Sea – a site of stunning marine biodiversity that is facing heavy pressures from overfishing, coastal development and other stresses.
Helene Marsh, professor emeritus of environmental science at James Cook University, says there are still about 100,000 dugongs living in the waters off the coasts of 40 countries, but the latest findings do not bode well. good for other animal populations in Japan and Southeast Asia. Queensland, Australia.
“It’s a sad story,” Professor Marsh said by phone on Friday, adding, “I don’t think this will be the last place where people can conclude that dugongs are functionally extinct.” power.”
A ‘serious reminder’
According to research by Annalisa Berta, professor emeritus of biology at San Diego State University.
Manatees belong to the order Sirenia, a biological order that includes dugongs and three extant species of manatees. All four are colloquially known as “sea cows,” but dugongs are the only ones that live entirely in salt water. It is also the only completely vegetarian cetacean in the world.
Over the centuries, the sirenians have inspired stories of mermaids and other magical creatures. Ms. Marsh said many legends are based on the idea that sirens, like the sirens in Homer’s “Odyssey,” attract sailors with magical properties. (The shallow waters, prehistoric times, where dugongs thrived, Tethys Seanamed after a sea goddess in Greek mythology.)
Manatees once had a larger range extending into the Western Atlantic and Caribbean, and once had several species of manatees. One of them, the Steller’s manatee, was a source of food for 18th-century hunters and explorers in the North Pacific, but it was declared extinct 27 years after its discovery in 1768.
Professor Marsh said Australia has the largest population of dugongs in the world today, largely thanks to a large, sparsely populated coastline with abundant seagrasses. The population off southern China, she added, has never been particularly strong because there isn’t much seagrass there.
Now dugongs can disappear forever from the shores of China, join in Yangtze River Dolphins and other species have disappeared from the country’s rivers and seas. Recent research describes the rapid collapse of dugongs in China since 1975 as a “sobering reminder that local extinction can happen in a very short time.”
A ‘dangerous decline’
The study by researchers at institutions in China, Greece and the UK is based on interviews conducted in the summer of 2019 with 788 fishermen along China’s southern coast. Only three sightings of dugongs have been reported within the previous 5 years.
The authors also analyzed dugong records in China, which showed that 257 dugongs were hunted there for food between 1958 and 1976. In contrast, there were no field observations of dugongs. dugongs in China after 2000.
It is possible that a “residual” population of dugongs has survived off the southern coast of the country, but the continued degradation of seagrasses and other coastal resources in the South China Sea makes the prospect of restoration less likely. population recovery is unlikely, the authors write.
One of the authors, Songhai Li at the Institute of Deep Sea Science and Engineering in China, referred the question to Samuel Turvey, co-author at the Zoological Society of London. He did not respond to a request for comment.
Harris Heng Weikang, a marine ecologist in Malaysia who has studied dugongs, says the study is limited because it relies heavily on interviews, in which sources can misidentify a dugout. marine mammals. “It would certainly be better to include direct evidence of the absence of this species,” he said.
But Professor Marsh, co-chair of the International Union for Conservation of Nature’s Sirenian Expert Group, said she saw no problem with the study’s methodology. “There may be a very low number of animals there that no one has seen for a while; that’s entirely possible,” she said. “But I think their conclusion is pretty solid.”
In 2015, the team classified dugongs as vulnerable to extinction, but the latest study highlights how the health of populations varies across regions, said Gabriel Grimsditch, the dugout program manager. at the United Nations Environment Programme.
“Relatively healthy populations can still be found in Australia and the Persian Gulf,” Mr Grimsditch wrote in an email from Abu Dhabi. However, outside of these two areas, most dugout populations are in dangerous decline, and research from China highlights the extinction threat they face within their range, he said. their behavior,” he said.
