南海北部大陆架鱼类群落的区域性变化

根据1982年至1984．年南海北部大陆架(海南岛以东至台湾浅滩西侧，水深40—260米范围内)底拖网鱼类资源调查取得的资料，运用聚类分析和多维尺度转换等方法，把该范圈内的鱼类群落按生物组成的特点，划分成5个区域性类型。它们所处的区域分别在：粤东海区的台湾浅滩西侧；40-米等深线附近；40米与100米等深线之间；100米与200米等深线之间；和大陆架外缘海域。分别阐述各区域性类型的生物组成、种类多样度和优势种等群落参数以及所处生态环境的主要特点。群落的区域性变化主要是由温度、盐度和深度的梯度及底质类型的差异而引起的，但水深可作为群落变化的主要指标。群落具有沿水深而成带分布的趋势，这一水深成带格局是群落对各环境因素变化的综合效应。大陆架外缘海域水深急剧增加，底层水温明显下降，鱼类群落相应地发生显著变化，因而初步认为，200米等深线可作为大陆架底栖鱼类群落的边界．本文还探讨了鱼类的区域性分布特点在合理调整各类群渔业资源利用率方面的前景。

THE REGIOAL CHANGES OF FISH COMMUNITY ON THE NORTHERN CONTINENTAL SHELF OF SOUT CHINA SEA

Samples of demersal fishes were taken with trawlnet seasonally for a2-year period (1982 to 1984) on the continental shelf, ranging in depth from 40 to280m. Fifty-eight stations are grouped into 5 major clusters using complementaryclassification and multi-dimensional scaling ordination techniques. These are bothbased on root-root transformed mean biomass data with the Bray-Curtis measure ofsimilarity. Faunal changes over 40,100, and 200m isobeths separate regions of relativefaunal homogeneity. One faunal assemblage can be identified in the area to the westof the Taiwan Bank, a second along the 40m isobeth, a third between the 40 and100m isobeths, a fourth between the 100 and 200m isobeths, and a fifth on the con-tinental sheif edge. Each assemblage was characterized by faunal composition, catchrates, species diversity and dominant species, as well as the environmental condi-tions the assemblage adapts to. Faunal changes are probably due to the gradients of temperature, salinity anddepth, as well as differences in sediment type. That the fish fauna are zoned withdepth may be established on the shelf. The zonation reflects joint response to envi-ronmental factors. The dramatic faunal changes at the shelf edge are mainly inducedby rapid increase in depth and decline in bottom temperature, and the 200m isobethmay be suggested as the boundary of the shelf fauna. The community structure was considerebly changed by fishing, especially inshallower zones. There might be potential for changing the patterns of fishing byarea regulation to obtain fine turning of the community.