The study investigated the zooplankton community composition and environmental factors in polyculture pond with high density of bighead carp(Aristichthys nobilis),yellow catfish(Pelteobagrus fulvidraco)and silver carp (Hypophthalmichthys molitrix.)The ponds were treated with 1/4 block(group A),1/2 block(group B)and no block (group C) meshes to investigate whether the blocking regulate the survival pressure of zooplankton population. The re-sults showed that TSS decreased significantly (P<0.05) in groups A and B, while nutrients as TN and TP significantly increased (P<0.05) in these two groups. The species of protozoa and rotifers in all groups were relatively high, account-ing for 30.4%-36.6% and 51.6%-57.0%, respectively, while species of cladocera and copepods were relatively lower. There was no significant difference in species composition of each group, and species diversity (H') in groups A and B were significantly higher at two sampling times (July 9thand July 23rd) than that in group C. In addition, the domi-nant populations in all groups were protozoa and rotifers, but rotifers tended to decrease in later time point. Moreover, the dominant species Moina macrocopa disappeared in group C overtime,while it still presented in group A and B. There were no significant difference in the biomass of rotifers and protozoa in each group during the experiment, while the total biomass of cladocera and copepods was significantly higher in group B than those in groups A and C, indicat-ing that blocking culture could reduce the survival pressure of large zooplankton population and slow down the decline of biomass. These results would provide a positive guide in maintaining ecological balance and increase nature food of bighead carp in the high diversity culture pond.%研究在高密度鳙和黄颡鱼、鲢混养模式下, 通过在池塘中设置1/4拦网(A组)、1/2拦网(B组)和无拦网(C组)处理和分析养殖期不同处理组的水质特征和浮游动物群落结构, 来探讨设置拦网是否会减轻浮游动物种群的生存压力, 以保证水体中大型浮游动物的生物量.结果显示, A、B组TSS明显降低(P<0.05), 但TN、TP等营养盐显著增高(P<0.05).各处理组中的原生动物和轮虫的种类相对较多, 分别占比为30.4%-36.6%和51.6%-57.0%, 枝角类和桡足类种类相对较少.各处理组的物种组成变化不明显, 物种多样性(H')仅在7月9日和7月23日2次采样中, A、B组显著高于C组(P<0.05), 其他时间各处理组无明显差异.各处理组中的主要优势种群为原生动物和轮虫, 但轮虫在实验后期趋于小型化.另外, 大型优势物种多刺裸腹溞Moina macrocopa随着采样时间在C组中消失, 在A、B组仍存在.轮虫和原生动物的生物量在实验期间各处理组中的变化不显著, 枝角类和桡足类总生物量则是在B组显著高于A组和C组, 说明拦网分区养殖在一定程度上能有效地减轻大型浮游动物种群的生存压力, 减缓其生物量的骤降.研究结果对维持池塘浮游动物生态平衡和增加池塘中鳙的天然饵料具有积极的指导作用.
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