太湖新银鱼种群摄食对小江浮游动物群落结构的影响

为探究三峡水库典型支流小江太湖新银鱼（Neosalanx taihuensis）种群摄食对浮游动物群落结构的影响，于2019年1~12月逐月对太湖新银鱼与浮游动物样品进行采集并分析太湖新银鱼胃含物组成与浮游动物群落结构特征。分析结果表明：（1）太湖新银鱼的饵料生物主要为桡足类（相对重要指数百分比（IRI%）=79.97%），其次为枝角类（IRI%=18.86%），轮虫占比较少（IRI%=0.001%）。（2）3至6月（太湖新银鱼春群繁殖期）太湖新银鱼生物量迅速上升，并在5、6月维持较高水平的生物量，而浮游动物群落结构呈现小型化趋势，生物量由28.93 mg/L下降至1.13 mg/L；密度由21173.39 ind./L增加至26808.23 ind./L。7月小江禁捕结束，太湖新银鱼生物量开始急剧下降，小江浮游动物中桡足类和枝角类的密度与生物量迅速升高，于8月（密度为151.98 ind./L；生物量为3.39 mg/L）达到全年最高。（3）在太湖新银鱼生物量较高的时期，由于太湖新银鱼对于枝角类和桡足类具有较强的选择性，导致水体中枝角类和桡足类生物量占比（17%~58%）显著低于其它时期（P<0.05）。由此认为，太湖新银鱼生物量与浮游动物群落结构变化存在较强的关联性，太湖新银鱼种群摄食的下行效应可能是小江浮游动物生物量下降及群落结构小型化的关键原因。明晰太湖新银鱼种群生长与浮游动物群落结构的动态变化关系可为小江水华暴发的控制与水生态健康管理提供理论依据。

Effects of Neosalanx taihuensis population feeding on zooplankton community structure in Xiaojiang River

In order to explore the effect of Neosalanx taihuensis feeding on zooplankton community structure in Xiaojiang River, a typical tributary of the Three Gorges Reservoir. From January to December 2019, we collected samples of N. taihuensis and zooplankton in Xiaojiang River and analyzed the composition of stomach contents of the N. taihuensis and zooplankton community structure. The results showed: (1) The main bait organisms for N. taihuensis are copepods (IRI%=79.97%) , followed by cladocerans (IRI%=18.86%) , and rotifers account for less (IRI%=0.001%). (2) March to June, the biomass of N. taihuensis increased rapidly and maintained a high level in May and June, while the zooplankton community structure showed a trend of miniaturization. The biomass of zooplankton decreased from 28.93 mg/L to 1.13 mg/L; the density increased from 21173.39 ind./L to 26808.23 ind./L. As the fishing ban ended in Xiaojiang River in July, we found that the biomass of N. taihuensis began to decline sharply. Otherwise, the density of copepods and cladocerans in Xiaojiang River increased rapidly, reaching the highest in August, which the density was 151.98 ind./L, the biomass was 3.39 mg/L. (3) During the period of high biomass of N. taihuensis, the biomass proportion of neopheles and copepods was significantly lower (17%-58%) than that in other periods (P<0.05), because N. taihuensis has strong selectivity for cladocerans and copepods. Therefore, it can be concluded that there is a strong correlation between the biomass of N. taihuensis and the changes of zooplankton community structure. The top-down effect of feeding of the N. taihuensis population may be the key reason for the decline of zooplankton biomass and the miniaturization of community structure in the Xiaojiang River. Clarifying the dynamic relationship between the growth of N. taihuensis population and zooplankton community structure can provide a theoretical basis for the control of algal blooms and the health management of water ecological in Xiaojiang River.