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根据1991—2011年间3个代表年冬季长江口渔场的调查数据,对该海域游泳动物群落的年代际变化进行了研究。结果表明:1991—2011年,游泳动物种类数总体表现为升高的趋势,其中鱼类的增加幅度较小,甲壳类和头足类的增加幅度较大。以重量和尾数为代表的资源密度指数均表现出先下降后升高的趋势。平均体重先呈现急剧下降然后继续小幅下降的趋势。1991年优势种类数为7种,2001年为9种,2011年为7种,后2个年份和1991年相比,优势种发生了较大的更替。细点圆趾蟹(Ovalipes punctatus)和龙头鱼(Harpadon nehereus)为3个年份的共同优势种。游泳动物的站位平均种类数呈现持续升高趋势,而站位平均丰富度指数、多样度指数和均匀度指数则呈现出先升高再降低的趋势。1991和2001年、1991和2011年之间的平均相异性较高,均超过60%,而2001和2011年之间的平均相异性较低,为36.05%;引起群落差异的主要种类数呈增加的趋势,生态类群也逐渐扩大。游泳动物长度谱呈现逐渐变窄的趋势,主要是由于群落中的生物种类演替、小型鱼类数量增多和大型鱼类的群体年龄结构降低等原因造成的。
Based on the survey data of the winter estuary fisheries in the three representative years from 1991 to 2011, the interdecadal variation of the swimming fauna in this area was studied. The results showed that from 1991 to 2011, the number of species of swimming animals showed an overall upward trend, with the increase of fish species being small and the increase of crustaceans and cephalopods larger. Resource density index represented by weight and mantissa all showed a trend of first decreasing and then increasing. Average body weight showed a sharp decline and then continued to decline slightly. There were 7 dominant species in 1991, 9 species in 2001 and 7 species in 2011, and the dominant species changed greatly in the latter two years compared with 1991. Ovalipes punctatus and Harpadon nehereus are the common dominant species for three years. The average number of species in swimming animals showed an increasing trend, while the stations of average abundance index, diversity index and evenness index showed the trend of first increasing and then decreasing. The average disparity between 1991 and 2001 was over 60% between 1991 and 2011, with a low average of 36.05% between 2001 and 2011, with the number of major species causing community differences increasing The trend of ecological groups also gradually expanded. The length spectrum of swimming animals showed a trend of becoming narrower, mainly due to the succession of species in the community, the increase in the number of small-sized fish and the decrease in the age structure of large-scale fish populations.