The dugong, a gentle creature said to have inspired tales of mermaids and sirens, has now been declared extinct in China after the degradation of its habitat and historical hunting. Only three people out of hundreds surveyed from coastal communities in China reported having seen the dugong in the past five years, a new study found. Fortunately, the dugong is still alive elsewhere in the world, though in alarmingly low numbers.
Although they're social animals, dugongs are often encountered either alone or living in pairs. The dugong is one of the four living species of the order Sirenia, which also includes three species of manatees. They are aquatic animals that live in coastal marine waters, especially bays, and mainly eat seagrass, reaching about 2.5 meters in length and can weigh up to 900 kilograms.
Dugongs (Dugong dugon) have been documented in Chinese waters for several hundred years and into the twentieth century. However, its habitats overlap with the activity areas of fisheries and other marine resource users, making them vulnerable to human pressures. The species has been listed globally as vulnerable by the IUCN.
Scientists at the Zoological Society of London (ZSL) and the Chinese Academy of Science reviewed historical data on where the dugongs had been previously found in China. They did an interview survey to collect local data and analyzed records from fishery captures, strandings, bycatch, field surveys and accidental sightings.
“Our new study shows strong evidence of the regional loss of another charismatic aquatic mammal species in China – sadly, once again driven by unsustainable human activity,” Samuel Turvey of ZSL’s Institute of Zoology, told The Guardian. “The findings should be a wake-up call to prioritize conservation efforts in China and elsewhere.”
The researchers found that there hadn’t been any verified sightings of dugongs in China since 2000. They also turned to citizen science and interviewed almost 800 community members living in coastal regions. On average, residents said they've not seen a dugong for 23 years, with three people seeing one in the past five years, though their claims cannot be verified.
This led them to declare the dugong functionally extinct, meaning it’s no longer viable to sustain itself. Even if some individual dugongs still remain in Chinese waters, the population decline experienced by the species in recent decades is unlikely to be halted or reversed under the continuing deterioration of coastal ecosystems, they said.
The dugongs are dependent on seagrass, a marine habitat that is being degraded fast by human impacts from water pollution to coastal development. Seagrass beds are also vulnerable to a process known as eutrophication, where algal blooms form due to the increase of nutrients in the water and this prevents seagrass photosynthesis.
While seagrass restoration efforts are on their way in China, the process can take a long time and it may be too late for the dugong populations that live there. The UN estimates that about 7% of seagrass habitat is lost every year because of climate change, unregulated fishing, coastal development, and agricultural pollution.
Chinese waters are home to about one-third of the world's marine mammal species. However, as with dugongs, many other species are also experiencing rapid declines, such as the recent extinction of the Yangtze River dolphin (Lipotes vexillifer). This highlights the need to improve marine conservation efforts, the researchers said.
The study was published in the journal Royal Society Open Science.