东海区沙海蜇的动态分布

Dynamic distribution of Stomolophus meleagris in the East China Sea Region

根据2003-2005年6月和9月东海区中、北部海域沙海蜇（Stomolophus meleagris）的监测结果，分析沙海蜇的生物量、分布、栖息环境及其与海水温度、盐度间的关系，调查范围为29°00′～34°00′N，127°00′E以西至机轮底拖网禁渔区线。结果表明，2003年6月～2005年6月，沙海蜇出现样点内的平均生物量分别为1555kg／h、1139kg／h、839kg／h。2003年9月-2005年9月沙海蜇出现样点内的平均生物量分别为7144kg／h、2292kg／h、608kg／h。2003-2005年6月和9月，东海区沙海蜇均呈现生物量逐年降低、分布海域面积逐年减少、分布区逐年往北偏移的趋势。6月，东海区沙海蜇分布区内的表层温度为17-25℃，底层温度为10-19℃，表层盐度为23-33，底层盐度为31-34．5；6月最适生存的表层温度为17-21℃，底层温度为15-18℃，表层盐度为28-32，底层盐度31-32．5。沙海蜇为偏冷水性，高盐种类。在春、夏季黄海冷水团势力强的年份，沙海蜇的发生和危害程度严重；而在春、夏季长江冲淡水势力强的年份，沙海蜇的发生较少，分布偏北。

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. rneleagris 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.