Population Viability Analysis Revealed the Vulnerability of Yangtze Finless Porpoise (Neophocaena asiaeorientalis) in Poyang Lake

Poyang Lake in China is the most critical habitat and final refuge for the Yangtze finless porpoise (Neophocaena asiaeorientalis), YFP. In 2022, its population reached approximately 492 individuals, an increase of 35 from the 457 individuals recorded in 2017, showing a steady upward trend. The infrequent movement of YFPs between Poyang Lake and the Yangtze River represents a considerable threat to the long-term viability of this population. Additionally, serious water shortages in the lake during the dry season have led the government to consider the establishment of a hydraulic project. Therefore, a reliable risk assessment and quantitative analysis of conservation scenarios are urgently needed for this population. Population viability analysis of the YFP population in Poyang Lake was conducted using the VORTEX software. The baseline model predicted a probability of extinction of 0.241 over the next 100 years, with no probability of extinction in the first 30 years; the genetic diversity would be on a continuous downward trend and decline by 91.5%. The comprehensive protection model predicted a probability of extinction of 0.0028 and that the genetic diversity would be maintained at about 0.996 in 100 years. Breeding rate, sex ratio at birth, mortality rate, and gene flow were the factors that were sensitive to maintaining population viability. The results showed that the population of YFPs in Poyang Lake was at a high risk of extinction due to the decline in genetic diversity and the higher mortality and lower birth rate caused by habitat degradation. A total ban on productive fishing and the rescue and interchange of YFPs are conducive to enhancing the viability of the YFP population in Poyang Lake.