中文摘要：

利用2003年6月和2006年6月在长江口及邻近海域进行的两次大面调查所采集的浮游动物网采样品，对长江口及邻近海域水母类的种类组成、优势种、数量分布及生态类群等进行了探讨。结果表明：研究水域共记录水母类77种，其中水螅水母60种，管水母12种，钵水母1种，栉水母4种。优势种有：五角水母（Muggiaea atlantica），双生水母（Diphyes chamissonis），拟细浅室水母（Lensia subtiloides），四叶小舌水母（Liriope tetraphylla），两手筐水母（Solmundella bitentacklata），嵊山秀氏水母（Sugiura chengshanense）和瓜水母（Beroe cucumis）等。其中水螅水母类的优势种存在较大的年际变化，2003年为嵊山秀氏水母，2006年为四叶小舌水母和两手筐水母。研究水域内水母类平面分布不均匀，2003年平均丰度为13.3个／m^3，除在长江口外存在一个由河口低盐种贝氏拟线水母（Nemopsis bachei）大量聚集形成的高值区外，在舟山群岛南部还存在一个密集中心；2006年水母类丰度略有上升，平均丰度为16．0个／m^3，与2003年相比，其密集中心向东北部偏移。2006年6月研究海域温、盐较2003年同期均大幅升高是造成两航次优势种类更替及水母类分布变化的主要原因。

英文摘要：

The present study was conducted on two surveys of the Changjiang River Estuary and its adjacent waters in Jun. 2003 and Jun. 2006. The species composition and dominant species of medusa as well as their abundance distributions and ecological characters were analyzed. A total of 77 species were identified, including 60 of Hydromedusae, 12 of Siphonophore, 1 of Scyphomedusae and 4 of Ctenophore. The dominant species were Muggiaea atlantica, Diphyes chamissonis, Lensia subtiloides, Liriope tetraphylla, Solmundella bitentachlata, Sugiura chengshanense and Beroee cucumis. The Hydromedusae dominant species changed dramatically in these two cruises. The abundance distribution in the investigated area was relatively uniform. The medusa abundance was lower in Jun. 2003 （13.3 ind/m^3） than that in Jun. 2006 （16.0 ind/m^3）. The peak value area of the abundance drifted more northeastward in Jun. 2006 than that in Jun.2003. The temperture and salinity in Jun.2006 were higher than those in Jun.2003, which were the main reasons leading to changes of the dominant species and distribution of medusa in the two surveys