三娘湾游泳动物种类组成及群落结构分析

广西三娘湾是中华白海豚（Sousa chinensis）的重要栖息海域，为了解该海域游泳动物的种类组成情况，于2011—2012年在该海域开展了秋季和春季两次调查，用相对重要性指数、物种多样性指数、相对资源密度以及数量生物量比较曲线（ABC曲线）等指标分析了该区域的游泳动物种类组成特征和群落结构稳定性。结果表明:该调查海域共鉴定游泳动物100种，隶属15目41科72属(其中鱼类最多，达65种），优势种多为鳀科、鲱科及鲾科等小型鱼类；两个季节多样性水平均不高，分布上多为一些饵料鱼类，种类组成小型化、低值化明显；秋季及春季的资源密度分别为888.59 kg/km2和554.62 kg/km2，与南海北部大陆架区其余海域相似，说明该海域资源水平不高，处于过度开发状态；ABC曲线显示，三娘湾海域秋季及春季的群落结构均受到一定程度扰动，种类组成均以生长快、性成熟早的小个体物种为主。

Analysis of Species Composition and Community Structure of Nekton in Sanniang Bay

Sanniang Bay is an important habitat area for the Chinese white dolphin(Sousa chinesis).In order to understand the species composition of the nekton in this area,based on the fixed point survey data in Sanniang Bay,Guangxi,from November 2011 to March 2012,the index of relative importance(IRI),species diversity,relative resource density and Abundance Biomass Comparison(ABC) curve were used to analyze the species composition and evaluate the stability of community structure.The results showed that a total of 100 species was identified involving 4 classes,15 orders,41 families,72 genera,and there were 65 fish species which was the largest number,accounting for 65%.The most dominant species were belonged to Engraulidae,Clupeidae and Leiognathae,while the diversity level of the autumn and spring was not high.The distribution of the species was mostly small-sized forage species,which had a positive effect on the feeding of Chinese white dolphin.The resource densities in autumn and spring were 888.59 kg/km2 and 554.62 kg/km2 respectively,which were similar to the other areas of the northern shelf of the South China Sea.The ABC curve showed that the community structure of Sanniang Bay was disturbed to some extent in autumn and spring,and the species composition was dominated by r-selection species(small individual species with fast growth and early sexual maturity).