Interview-based sighting history to investigate the historical range and dynamics of dugongs in China.

The dugong (Dugong dugon) is the first marine megafauna to be declared functionally extinct in China, yet its historical range and extinction dynamics remain poorly understood. Sighting histories were thus collected from 841 fishers to investigate this information based on a large-scale interview survey across the entire dugong historical range in 2024. Apart from a single incidental capture reported in 2021, there have been no other records reported by informers since the last stranding in 2008, with the average date of the last sighting being in 1983 ± 14. A notable discovery was that dugongs were once sighted in Shantou, extending the known historical range northward by 500 km in mainland China. We also document extensive past dugong sightings and seagrass meadows in the South China Sea, beyond the previously known range. The spatio-temporal analysis indicates that dugongs disappeared almost simultaneously across their entire historical range, without undergoing significant range contraction. These findings confirm previous conclusions that dugongs are now functionally extinct in China. Our study reveals how a once widely distributed marine mammal experienced a population crash within just 20-30 years, serving as a serious warning for dugong conservation worldwide and highlighting the urgent need to protect other marine megafauna in the South China Sea.