2010年莱州湾底层渔业生物群落结构及季节变化

Seasonal changes in the community structure of the demersal fishery in Laizhou Bay

根据2010年春季(5月)、夏季(8月)、秋季(10月)和冬季(12月)在莱州湾进行的19站位弓子网调查数据,对弓子网渔获物组成、底层渔业生物群落结构及季节变化进行了研究。结果表明,全年弓子网调查共捕获渔业生物78种,春季种类最少,而其他季节种类数接近。弓子网渔获物质量组成由高到低依次为甲壳类、鱼类、头足类、贝类;生物量的季节变化趋势由高到低依次为秋季、春季、冬季、夏季。生物量各季节的空间分布差异明显,主要由少数优势种类的季节分布差异引起。优势种季节更替明显,全年优势种为玉蟹科、寄居蟹、斑尾刺虾虎鱼(Acanthogobius ommaturus)和扁玉螺(Neverita didyma)。丰富度指数(D)、多样性指数(H')和均匀度指数(J')均以夏季为最高,而其他3个季节则较为接近。分析表明,冬季与其他季节的Jaccard种类相似性较低;春季群落的生物量和丰度组成与其他季节的Bray-Curtis相似性均较低。各季节的迁移指数均大于100,群落稳定性较差。莱州湾底层生物群落主要由小型、低质种类构成,个体平均质量较小,群落优势种类季节更替明显。为保护莱州湾渔业资源,应严格控制弓子网作业渔船数量。

We evaluated seasonal changes in the community structure of a demersal fishery in Laizhou Bay,China using data collected by beam trawl in May,August,October,and December of 2010.We captured fish at 19 sites in the study area（37°12′.37°40′N,119°05′.120°00′E）.We collected a total of 78 species.The number of species was lower in spring than in other seasons.In terms of biomass,crustaceans were the most dominant category,followed by fish,cephalopods,and shellfish.The total biomass was highest in autumn,followed by spring,winter, and summer.The spatial distribution of biomass differed significantly among the seasons,primarily because of changes in the seasonal distribution of a few dominant species.We used the index of relative importance（IRI） to estimate the importance of each species in the community.The dominant species,which was defined based on an IRI value of 1000,were Leucosiidae spp.,Diogenes spp.,Acanthogobius ommaturus,and Neverita didyma.The values for the Margalef richness index,Shannon-Wiener diversity index,and Pielou＇s evenness were higher in summer than in the remaining seasons.We used Jaccard＇s similarity index to assess the similarity of species among the seasons.Jaccard＇s similarity was low between winter and the other seasons,but high between spring and summer,summer and autumn,and spring and autumn.We used ANOSIM to evaluate the dissimilarity of the fish community between seasons.The community similarity was low between spring and the other seasons both for biomass and abundance.We conclude that：（1） in Laizhou Bay,larger-sized,high-value,complex-age-structured species have been replaced by small,low-value,simple-age-structured species.（2） The mean body weight is low and the community is dominated by smaller individuals.（3） The community consists of relatively few dominant species,and is unstable,evidenced by seasonal replacement of the dominant species.（4） Beam trawling is harmful to the fishery and should be limited.