Dynamic distribution of Stomolophus meleagris in the East China Sea Region

Since the mid-1990s,jellyfish blooms have been occurring every year in the northern part of the East China Sea and the Yellow Sea,which have caused ecological disaster in those areas.The main species in the blooms include Somolophus meleagris and Cyanea sp.,and S.meleagri is the dominant species.We monitored the dynamic distribution of S.meleagris in the central and northern parts of the East China Sea Region in Junes and Septembers of 2003,2004 and 2005.Based on the monitoring results,the biomass,distribution and inhabited environment of S.meleagris,as well as their relationships with water temperature and salinity were analyzed.In Junes of 2003 to 2005,the mean biomasses of S.meleagris in the monitoring stations were 1 555 kg/h,1 139 kg/h and 839 kg/h,respectively.In Septembers of 2003 to 2005,the mean biomasses were 7 144 kg/h,2 292 kg/h and 608 kg/h,respectively.The results suggest that,from 2003 to 2005,the biomass and distributed range of S.meleagris in June and September decreased and tended northward.The temperatures and salinities of sea surface water and bottom water within the distributed areas of S.meleagris in Junes from 2003 to 2005 were 17-25 ℃,10-19 ℃,and 23-33 and 31-34.5,respectively.Assuming the area with the highest biomass was the optimum environment for S.meleagris,the optimum water temperature and salinity of sea surface and bottom for S.meleagris in June in the East China Sea Region were 17-21 ℃,15-18 ℃,and 28-32 and 31-32.5,respectively.Thus S.meleagris is a relatively low-temperature and high-salinity species.The water masses which affect the distribution of S.meleagris include Yellow Sea Cold Water Mass(YC),East China Sea Warm Water Mass(EW) and Yangtze Diluted Water(YD) in June.YC is a water mass of low temperature and moderate salinity,while EW is a water mass of high temperature and high salinity,and YD is a water mass of low salinity.YD usually extends northeastwards in summer.The sea surface water temperature in the distribued range of S.meleagris was lower in June of 2003 than those in Junes of 2004 and 2005,which was caused by the strong YC in 2003.Since S.meleagris is a relatively low temperature species,the stronger YC in 2003 induced the largest blooms and widest distribution of S.meleagris during 2003-2005.Thus in spring and summer,if YC is strong,S.meleagris would bloom in the East China Sea Region.The salinity in the distribution area of S.meleagris was lower in June of 2005 than those in Junes of 2003 and 2004,which was caused by the strongest YD in June 2005.Since S.meleagris is a high-salinity species,the strong YD resulted in the smallest blooms and occurrence range of S.meleagris in 2005.Thus,in spring and summer,if YD is strong,S.meleagris blooms would be small and distributed narrowly.The blooms would also occur further northwards in the East China Sea Region.[Journal of Fishery Sciences of China,2007,14(1):83-89]