Population structure and growth status of Yangtze finless porpoise in the sand pits waters of southern Songmen Mountain, Poyang Lake

Abstract:

A large-scale emergency rescue operation for Yangtze finless porpoise was carried out in November 2022 and February 2023 in the southern sand pit waters of Songmen Mountain in Poyang Lake.This paper describes the population structure and growth status of Yangtze finless porpoise for the first time, using the physical examination data obtained during the rescue period and the results of the subsequent acoustic survey of Yangtze finless porpoise in this area. The average body length of this population is （135.01±16.95） cm, the average body mass is （42.37±14.71） kg, the average maximum body circumference is （88.32±9.32） cm, the average body mass index is （22.83±4.72） kg/m², and the average body circumference index is 65.88%±5.86%. The average thickness of axillary fat layer is （2.51±0.55） cm, the average thickness of anal fat layer is（2.47±0.31） cm, and the average thickness of maximum body fat layer is （2.08±0.34） cm； the population structure was relatively large for young individuals and more males, and the population showed an extended type； the population density of Yangtze finless porpoise in the waters was greater than 2 heads/km², and the population size was about 39 to 111 individuals. On the whole, the Yangtze finless porpoise population is in good health and has good breeding potential, and the attention and protection of the Yangtze finless porpoise population should be strengthened.