南海北部大陆架鱼种组群初步分析

根据南海北部大陆架水深40—200米范围内200网次底拖网鱼类调查资料,计算125个鱼种在采样中同时出现的 Jaccard 群落系数,用聚类分析导出8个组群。分析鱼种组群格局与环境因素之间关系的结果表明,组群中所包含的鱼种具有相似的环境需求特性,从而按组群概括阐述了各鱼种的环境适应特点和分布区域。优势鱼种组群对环境的适应范围广,分布遍及整个调查海区。其余各组群的形成与一定的环境条件相联系,并沿等深线分布在特定水深范围内。陆架外缘环境因素的明显变化,成为大多数陆架鱼种分布的阻限。本研究还以鱼种组群为基础对群落格局作了反相分析。

A PRELIMINARY ANALYSIS OF FISH SPECIES GROUPS ON THE NORTHERN CONTINENTAL SHELF OF SOUTH CHINA SEA

Demersal trawl Gollections of fishes were made in 4 seasons (May,1983 to February, 1984) at 50 stations distributed between 40 and 200--m isobethson the continental shelf. Based on presence--absence data of 125 fishes recorded atleast 3 times in the 200 hauls, the species are clustered by group--average classifi-cation of an association matrix of Jaccard's coefficient of community. Eight co-occurrent species groups are derived. The dominant species group is furtherdivided into 4 subgroups. To illustrate the environmental requirements of fishes,the abundances of each species are arranged along gradients of depth. bottomlayer temperature, salinity and sediment types. The gradient analysis shows thatthe clustering procedure groups the fishes that have similar reactions to propertiesof the environment. Thus, the groupings are used to summarize environmentalrequirements and distribution ranges of fishes. A subgroup of indifferent speciesspreads and dominants throughout the shelf area. Other species groups and sub-groups are associated with certain environmental conditions and their distributionszone with depth. The dramatie increase in depth and decrease of temperature onthe shelf edge coincide with the distributional limits of most shelf fishes. Theabundances of all species groups decrease or disappear on the shelf edge. but theabundances of the species group characterizing shelf edge and slop environmentsincrease with depth. The species groupings as inverse analysis of communitypatterns indicate that due to environmental changes, the assemblages of fishesvary with depth and faunal changes are rapid on the shelf edge region. This conforms the results of previous normal analysis of the community.