Study on ecology of meso-small pelagic copepods in the Southern Yellow Sea and the East China SeaI. quantitative distribution

Based on the data acquisitioned through the seasonal investigation in the Southern Yellow Sea and the East China Sea(28°00′-34°00′N,121°00′-127°00′E), the abundance of mesosmall copepods sampled by net of mesh size 0.160mm in the months of February, May, August and November standing for spring, summer, autumn and winter respectively, 1981 was studied. The investigated results show that the seasonal mean abundance of mesosmall copepods in the four seasons was 376.4 ind·m-3. The variation of abundance appeared a peak, highest in summer (846.34 ind·m-3), then in spring (338.91 ind·m-3) and autumn (204.96 ind·m-3), and lowest in winter (115.41 ind·m-3). The seasonal mean abundance in the northern part of the southern Yellow Sea (32°N) and the East China Sea (28°～32°N) was 271.05 ind·m-3 and 403.59 ind·m-3 respectively. The seasonal variation trend of abundance was in correspondence with that in the whole investigated area. However, in summer the mean abundance (492.04 ind·m-3) in the Southern Yellow Sea was obviously lower than that in the East China Sea (938.2 ind·m-3). In accordance with the results of dominance and regression contribution analysis, it shows that the abundance distribution was mainly determined by the distribution of Oithona similis, Paracalanns parvus, Corycaeus affiris etc. in the seasons of winter, spring and summer, but in autumn season mainly dependent on the distribution of Aegisthus mucronatus, Calocalanus pavo, Calocalanus pavoninus, etc. The results of multifold regression analysis of temperature,salinity and abundance show that the factors affecting the variation of total abundance included temperature in summer and winter and salinity in spring. 