Relationship between pelagic Decapods and environmental factors in the East China Sea

Based on the data of four seasonal censuses in the East China Sea(23°30'-33°N,118°30'-128°E) during 1997-2000,the distribution and the seasonal changes of pelagic Decapods abundance,regression contribution of dominant species abundance to total abundance and environmental effects on pelagic Decapods abundance were studied with qualitative and quantitative methods.The results showed clear seasonal changes of pelagic Decapods abundance, which peaked in summer (451 ind/100 m~(3)) and autumn (71 ind/100 m~(3)), but dropped to the lowest in spring (24 ind/100 m~(3)). In spring, there was nearly no pelagic Decapods in the northern shallow waters of the East China Sea (29°30'-33°N, 123°30'-125'E). Except for winter, pelagic Decapods showed a higher abundance in the offshore than in the off-sea in the rest three seasons. Based on the results of dominance and regression contribution analysis, the pelagic Decapods abundance was mainly governed by the abundance of Lucifor intermedius. Their abundance in summer and autumn, and the overall abundance in 4 seasons were remarkably related with water temperature, but not with salinity. In winter, the abundance was only related with salinity whereas in spring it was related with both water temperature and salinity. The high distribution area of pelagic Decapods gradually expanded northwards with the movement of Taiwan warm current from spring. In summer, a distribution area with abundance over 2 500 ind/100 m~(3) was observed in the converged areas by Taiwan warm current and the Fujian-Zhejiang coastal waters. In autumn, a high abundance area was formed in the converged area of Taiwan warm current and the Changjiang dilute waters. Water temperature and marine currents were found to be the most important environmental factors affecting the changes of pelagic Decapods abundance in the East China Sea.