Viewpoints on the study of economic thresholds of cotton bollworm
渤海浮游动物群落生态特点Ⅰ.种类组成与群落结构

Species composition and community structure of zooplankton in the Bohai Sea were studied with samples taken with medium plankton net in 1959.The results revealed that zooplankton in this area was dominated by temperate neritic speicies,including Paracalanus parvus,Acartia bifilosa,Paracalanus crassirostris,Oithona similis,Corycaeus affinis,Labidocera enchaeta and Sagitta crassa .The dominant species also included Centropages mcmurrichi,Calanus sinicus and Acartia pacifica, but their geographic distribution and seasonal changes were controlled by current from the Yellow Sea.There were also some warm water species occurred in the Bohai Sea and they were driven by the current from Yellow Sea.These species were Euchaeta rimana Bradford 1974, Euchaeta concinna,Pontella spinicauda,Cyclosalpa pinnata,Brooksia rostrata,Doliolum denticulatum,Sagitta enflata and Ostracoda.To understand the community structure,cluster analysis was used to analyze sample station data set,which showed there were two distinctive groups:One was the neritic group,and the other was oceanic group which was controlled by current from the Yellow Sea.Besides these two groups,there were some stations stayed in a transitional position.Such a community structure was clear in the spring(represented by May).In summer,different hydrographic features led to a complex community distribution patterns,and the differences between groups were not very significant.During fall and winter,driven by the northeast wind,no significant differences occurred.