Study on biological oceanography characteristics of planktonic copepods in waters north of Taiwan Ⅰ.Abundance distribution

On the basis of the investigation materials of 6 cruises in the waters north of Taiwan from 1987-1990,the distribution characteristics of planktonic copepods are discussed in the study from three aspects of abundance distribution,community feature and indicative species.The paper is the first part of the study.The results show as follows:the highest abundance of copepods occurred in spring and the lowest one in winter,while the abundance in summer and autumn was between the above two seasons.The copepod abundance in the west of the Kuroshio front was higher than that in the east of the front.There was a distribution tendency that higher abundance occurred in outshore area in summer and in nearshore area in winter,which corresponded with the trend of seasonal swings of the Kuroshio front.The higher copepod abundance appeared generally in the mixed areas of various water masses,especially in nearshore side of upwelling of the Kuroshio sub-surface water.However,in the Kuroshio subsurface main water,the abundance was low because of some factors such as low concentration of dissolved oxygen and so on.The vertical distribution trend was that the copepod abundance decreased with the increase of depth,and the diurnal vertical migration regularities of some species were probably the one of reasons that caused the abnormal distributions in some local waters.