三峡工程蓄水前后秋季长江口鱼类浮游生物群落结构的动态变化初探

对长江口及其邻近海域2002年秋季与2003年秋季鱼类浮游生物的调查资料进行比较,分析三峡工程蓄水前后秋季长江口鱼类浮游生物群落结构特征变化.结果发现,蓄水后鱼类浮游生物种类和数量比蓄水前有所增加,群落结构和时空分布特征发生了明显的改变,一些分布在黄渤海的种类如方氏云ND022等开始在东海出现,并且部分鱼类的生殖时间上也发生了改变.利用相对重要性指数（IRI）对长江口鱼类浮游生物进行优势度检验,其优势种成分也发生了很大的变化,虽仍是以小型种类为主,但原占绝对优势的日本ND023优势度开始逐渐下降,成为常见种,而康氏小公鱼的数量急剧上升.阐明了长江口鱼类资源的补充及群落结构和多样性变化规律及其与环境的关系,为动态监测三峡工程对河口生态环境的影响提供科学依据.

Dynamic Changes in the Ichthyoplankton Community Structure after the Sluice of the Three-Gorges Dam

An analysis was made of the data obtained in comprehensive surveys on the fisheries ecology and oceanography in the Changjiang River estuary. Eleven species of ichthyoplankton were recorded with 35 eggs and 29 larvae in November, 2002, while 14 species were recorded with 24 eggs and 85 larvae in November, 2003, which showed the species and quantities of ichthyoplankton in 2003 were more than those in 2002, and the ichthyoplankton community structure and its spatiotemporal dynamics were notably changed. The species of Sciaenidae were more than the others; Anguillidae, Callionymus spp. and Pseudosciaena crocea were new records in 2002. There were relatively more species of Sciaenidae in 2003; Anchoviella commersoni was a new record in 2003, but it was an absolutely dominant species, acconting for ca 64.2% of all the ichthyoplankton samples. In addition, Odontamblyopus rubicundus, Anchoviella zollingeri, Enedrias fangi, Pseudolaubuca engraulis, Chirocentrus dorab, and Trachinocephalus myops were all new records in the investigation area. Some species, such as Enedrias fangi in the Huanghai and Bohai Seas appeared in 2003 in the East China Sea, and some species changed their reproductive time. Based on their indices of relative importance, it can be seen that Sciaenidae, Salanx ariakensis and Lateolabrax japonicus were the dominant species in 2002, while Anchoviella commersoni, Saurida undosqamis and Trachinocephalus myops were the dominant species in 2003. Engraulisjaponicus was absolutely dominant quantity historicals, but recent 2 years investigations, shoneed that it had changed from a dominant species to an ordinary species. The above changes in ichthyoplankton community structure weere related to runoff, overfishing and pollution etc., but runoff is the most important factor that can cause changes in temperature, salinity etc., especially the construction of the Three-Gorges Dam, which has changed the runoff of the Changjiang River since the first sluice. So the changes in icthyoplankton species and quantity reglected the environmental factors changes in the ecosystem. The research of ichthyoplankton can provide dynamic monitoring for the influence of the Three-Gorges Dam on the estuary ecosystem.