Study on the spawning population fluctuation of Chinese sturgeons around the closure of Gezhouba Dam

Abstract

Based on the characteristics of the two cohorts in the spawning population of Chinese sturgeon, this paper established a theoretical method to estimate the resources of Chinese sturgeon by using the fishing data, and estimated the resource and its annual fluctuation of Chinese sturgeon in the Yangtze River from 1972 to 1990. The calculation showed that the annual average resource of Chinese sturgeon in the Yangtze River is 1727 ind from 1972 to 1980 with the annual recruitment of 1009 ind, and the population sizes were 1166 ind in 1981, 2309 ind in 1984 when the population reached its maximum. After 1984, the amount of resources decreased year by year. Therefore, the influence of the barrier by Gezhouba Dam and fishing on the resources of Chinese sturgeon was quantitatively estimated and compared. The results showed that the closure of Gezhouba in January 1981 led to 660 ind blocking in the upsteam and 349 ind in the downsteam from the cohort of 1980 then, the barrier coefficient, α , is 65%. In 1981, the catch of Chinese sturgeon was 1002 ind that implied the resource utilization rate was 86%. Outwardly, the effect of overfishing in 1981 was greater than that of Gezhouba Dam, but Gezhouba Dam greatly reduced the spawning area and migratory distance of Chinese sturgeon, and the impoundment of Three Gorges may affect the gonadal development and spawning conditions of Chinese sturgeon. So the impact of dam to Chinese sturgeons needs to be studied and analysed more for comprehensive protective measures.