东海大陆架鱼类群落的空间结构

根据1997～2000年东海大陆架水深30～200米海域4个航次的底拖网调查资料,运用多元分析(聚类分析和非度量多维标度(NMDS))、SIMPER以及BIO-ENV方法分析了东海鱼类群落的空间格局以及与非生物环境因子之间的关系。结果表明,东海大陆架海域鱼类群落在空间上可分为3个群落类型,分别为东海近海群落、东海大陆架外缘群落以及这两个群落之间的东海大陆架混合群落。东海大陆架鱼类群落的种类组成沿着水深梯度的变化明显,每种鱼类均有一定的水深范围。不同的流系具有不同的温盐特征,影响了鱼类的分布及其洄游,从而控制了不同鱼类群落类型的种类组成。东海大陆架鱼类群落类型中,大陆架外缘群落类型各调查季节在空间分布和种类组成上相对稳定,而东海近海群落类型和东海大陆架混合群落类型在夏季融合在一起,其它季节保持各自的空间结构。同时东海陆架区只在一种群落类型中出现的鱼类相对较少,多数鱼类同时出现在两个群落类型中或3个群落类型中,但是它们相对较集中的区域明显不同,在不同群落类型中的生物量和出现频率有很大的差异,这些鱼类在其不同的生长发育阶段由于对海洋环境的不同需求,它们根据繁殖或摄食需求而在东海陆架区范围内洄游以寻找最适的海洋环境,因此对3个群落类型定义是相对的,很难严格确定一个永久的鱼类群落地理区域,以形成相互隔离的鱼类群落,而且鱼类群落之间的边界随着季节不同发生变化。

Spatial structures of fish communities on the continental shelf of the East China Sea

We applied various multivariate statistical methods to analyze data collected from fisheries-independent bottom trawl surveys during 1997 to 2000 on the continental shelf(30-200m) of the East China Sea(ECS).The multivariate statistical analyses include cluster analysis,non-metric multidimensional scaling(NMDS)),SIMPER and BIO-ENV analyses.Based on the analyses,we identified spatial structures of fish communities and their relationships with environmental variables.Fish communities were classified into the three groups,offshore community in ECS,mixture community in ECS,and outer edge community of continental shelf in ECS.Fish community structures changed along depth gradients.Depth tended to be a limiting factor for the distribution of each fish species considered in this study.Currents had different characteristics of temperature and salinity and influenced the distribution and migration of fishes,and subsequently spatial and temporal structuring of fish species compositions.The spatial structure and compositions of fish species in the outer edge community remained relatively stable over all seasons.However,for the offshore and mixture communities,their boundaries disappeared in the summer,but maintained in other seasons.There were only a few species that were solely found in one community.The depth ranges of different fish species overlapped,but biomass and presence/absence of the species varied significantly along depth gradients.Different fish species tended to have different optimal habitats.Moreover,for a given fish species they might require different habitats in different stages of their life history.Thus,they might migrate within the continental shelf area to search optimal habitats.As a result,classification of the three communities should be considered relative,and the boundary between fish communities could change with seasons.We concluded that the determination of permanent geographic distribution area of fish community might not be possible.