葛洲坝截流前后长江中华鲟繁殖群体数量变动研究

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

根据中华鲟繁殖群体存在两个股群的特点,建立了一种利用捕捞数据估算中华鲟资源量的理论和方法,并估算出1972~1990年长江中华鲟资源量及其逐年变化.其中,1972~1980年长江中华鲟年均资源量为1727尾,年均补充量为1009尾;1981年的资源量为1166尾.1984年达到最大2309尾.1984年以后资源量逐年减少.在此基础上,对葛洲坝阻隔和捕捞对中华鲟资源量的影响进行了定量估算和比较,结果表明:1981年1月葛洲坝截流导致1980年股群被葛洲坝阻隔在上游的数量为660尾,下游数量为349尾,葛洲坝对中华鲟资源量的阻隔系数α为65%.1981年中华鲟过度捕捞量1002尾,资源利用率u达到86%.表面上看,1981年过度捕捞的影响大于葛洲坝的阻隔作用,但葛洲坝大大减少了中华鲟产卵场面积和洄游距离,加上三峡工程的运行,影响中华鲟性腺发育和产卵条件,需要加强研究,采取综合保护措施.

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, a, 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.