An age-structured population model of the Chinese sturgeon(Aciperser sinensis)

The estimation of the abundance of Chinese sturgeon, Acipenser sinensis, is of great significance to its conservation and the assessment of the ecological impact of hydropower construction. Based on its age-structure of the historical fishing data in the Yangtze River, we calculated the age-specific proportion of the adults, and then constructed an age-structured population model to estimate the abundance dynamics of A. sinensis, including the population sizes in the Yangtze River and the sea. Under the steady-state condition (prior to the Gezhouba river closure), we calculated that the amount of effective recruitment was 1 882 individuals every year, and the total number of the adult A. sinensis (female: 13–34 year old, male: 8–27 year old) was 32 260 individuals, with 15 310 of the male and 16 950 of the female. The numbers of adults in the Yangtze River (1 727 individuals) was 5% of the total in the Yangtze River and the sea. Using the sex ratio and old cohort proportion of historical fishing data, we estimated that the remnant spawning capacity ofA. sinensis was only 6.5% after the river closure of the Gezhouba Dam, and 68%–80% of the old cohort was obstructed by Gezhouba Dam in the upper river. Then we estimated the dynamics ofA. sinensis in the Yangtze River or/and the sea after 1981. The results show that after the river closure of Gezhouba Dam, the number of spawners in Yangtze River increased with the decrease of harvest number, and reached its peak in 1990 (about 2 200), then decreased rapidly, and was about 170 in 2010. The reduction of the spawning ground environmental capacity after the river closure of Gezhouba Dam was one of the reasons for the sharp decline of population size of A. sinensis.