Spatial and temporal distribution of pelagic Polychaeta in the East China Sea

According to four seasonal investigation data at 23°30′～33°00′N、118°30′～128°00′E in the East China Sea,the variation of quantity and distribution of pelagic Polychaeta,its contrast process of dynamics and it relationship with fishing ground in East China Sea were discussed.The results showed that the average abundance of pelagic Polychaeta was 23.68×10~(-2)/m~3 in autumn;higher than 8.59×10~(-2)/m~3 in summer,5.80×10~(-2)/m~3 in winter and 1.20×10~(-2)/m~3 in spring.The abundance of pelagic Polychaeta showed linear relation with 10m water temperature in summer,same as to the yearly abundance.It showed the positive relation with 10 m water temperature,whereas the negative relation with 10 m salinity in autumn,the abundance was not related with any water environment factors in spring and winter.The temperature played the main important role in seasonal variation of pelagic Polychaeta,salinity ranked after it.It was an obviously feature in East China Sea in autumnthat the horizontal distribution of pelagic Polychaeta was even.It was found the relation on the quantity fluctuation of pelagic Polychaeta closely linked with ebb and flow of warm current and continental water,as well as with duration of warm current from summer to autumn.At the East China Sea,high abundance area of the zooplankton always situated at area where different water mass converged especially in the area where warm water mass mixed with the Changjiang Dilute Water.The quantity of pelagic Polychaeta was high in the low salinity area caused by runoff from the continental river.The emergence of the high abundant area in autumn was significantly beneficial to the fishing ground for Scomber japonicus and Decapterus maruadsi in the north of the East China Sea.