长江口中华绒螯蟹成蟹资源现状及其繁殖特征

Resource status and reproductive characteristics of Eriocheir sinensis in the Yangtze Estuary

根据2017—2018年长江口中华绒螯蟹(Eriocheir sinensis)的调查数据,研究了长江口中华绒螯蟹成蟹资源的种群结构和繁殖特征。崇明西滩、崇明东滩、横沙浅滩和九段沙水域中华绒螯蟹的CPUE均值分别为(0.81±0.23)、(0.49±0.57)、(0.32±0.29)、(1.02±0.37)kg·(网·d)^-1。中华绒螯蟹规格在空间分布上呈由中游至下游逐步下降的趋势,在时间上各调查站位变化规律各有不同。中华绒螯蟹总体雌雄性比为0.36∶1,崇明东滩和横沙浅滩雌蟹比例随时间推移逐渐升高,九段沙雌蟹比例则一直维持在20%的水平,且显著小于其他3个调查站位。调查期间九段沙水域均可捕到抱卵蟹,抱卵率随时间推移先降低后升高。崇明东滩、横沙浅滩和九段沙抱卵蟹的相对繁殖力分别为(12.80±4.14)×10^2、(13.10±6.25)×10^2、(7.82±4.47)×10^2粒·g^-1。

As an important economic species in the Yangtze River,Chinese mitten crab Eriocheir sinensis(Decapoda,Brachyura)only gathers to breed in the estuarine areas.However,the population of E.sinensis has been decreasing year by year since the 1980s.To protect and rationally develop E.sinensis resource,it is necessary to study its resource status.Thus,the spatial and temporal distribution of E.sinensis resource were surveyed via gill nets in the Yangtze Estuary from 2017 to 2018.Meanwhile,the population structure and reproductive characteristics of adult E.sinensis in the Yangtze Estuary were revealed according to the survey data.Key results showed the mean CPUE values of Eriocheir sinensis in Chongming Xitan,Chongming Dongtan,Hengsha Shoal and Jiuduansha were(0.81±0.23),(0.49±0.57),(0.32±0.29)and(1.02±0.37)kg·(net·day)^-1,respectively.The spatial distribution of the size of Eriocheir sinensis showed a decreasing trend from the middle reaches to the lower reaches,and the changing regularity of each survey station was different in time.In this survey,the overall male-female ratio of Eriocheir sinensis was 0.36∶1.The proportion of female crab in Chongming Dongtan and Hengsha Shoal gradually increased over time,but the proportion of female crab in Jiuduansha remained at 20%,which was significantly less than those of the other three survey stations.During the investigating period,ovigerous E.sinensis could be caught in Jiuduansha,and the egg-holding rate decreased first and then increased with the passage of time.The relative fecundity of ovigerous E.sinensis in Chongming Dongtan,Hengsha Shoal and Jiuduansha were(12.80±4.14)×10^2,(13.10±6.25)×10^2 and(7.82±4.47)×10^2 eggs·g^-1,respectively,which were at a low level.Overall,the results revealed that the population of E.sinensis had been increasing gradually in the Yangtze Estuary from 2005.However,the carapace length and relative fecundity of adult E.sinensis were smaller than that of a decade ago.These results will provide theoretical basis for the rational utilization and protection of E.sinensis,also will enrich the basic theory of the variation rules of Eriocheir sinensis.