现代海洋牧场建设之我见

为探究筏式贻贝养殖生境鱼类资源养护功能，于2020年9－12月对枸杞岛筏式贻贝养殖生境(分表层区和底层区)及周边岩礁生境的鱼类进行了多网目组合刺网采样。应用相对重要性指数IRI、多样性指数并结合等级聚类、非度量多维标度排序(nMDS)分析鱼类组成和群落结构。结果显示，在2种生境中共采集鱼类55 种，隶属于10目34科47属，其中贻贝养殖生境采集到37种(底层和表层分别为29和20种)；岩礁生境共采集到40种。在鱼类组成上，中国花鲈和鲻是贻贝养殖生境表层区的典型优势种，而黄姑鱼和褐菖鲉是贻贝养殖生境底层区的典型优势种；褐菖鲉同时也是岩礁生境的典型优势种。多样性分析表明，贻贝养殖生境的总体鱼类多样性要高于岩礁生境，但尚不显著。多元分析显示，各月份2种生境中的鱼类群落格局均可分为3种类型，虽与养殖表层区、养殖底层区和岩礁区并非严格一致，但各群落间差异依然显著。研究表明，大规模筏式养殖设施的存在吸引了众多中上层鱼类及底层鱼类，也为岩礁生境优势鱼类提供了额外的栖息环境，发挥了近似于浮鱼礁系统的资源养护作用。研究结果可为岛礁海域海洋牧场目标种的选择和人工生境构建模式的应用提供重要参考。

Views on modern marine ranching

The rapid development of marine aquaculture in China, especially that of raft shellfish culture, not only contributes directly to China’s economic benefits, but also facilitates fishery resources conservation to a certain extend. Large-scale raft culture, in a sense, has played a role of artificial floating reefs, providing temporary or permanent feeding or sheltering habitats for fish, which coincides with the core idea of marine ranch development based on floating reef systems. Fish assemblages and their community characteristics in raft mussel farming habitats play key roles in understanding functions of floating artificial reef system in marine ranching area. Hence, fish composition and community structure in surface and bottom levels of a mussel farming habitat in Gouqi Island waters and an adjacent rocky reef habitat were analyzed based on data collected by multi-mesh trammel nets from September to December 2020. Index of relative importance (IRI), species diversity indices and non-metric multidimensional scaling (nMDS) analysis were used. A total of 55 fish species belonging to 47 genera in 34 families of 10 orders were collected from two habitats. Among which, 37 species were collected from mussel farming habitat, including 29 species from bottom level and 20 species from surface level; 40 species were collected from rocky habitat. In terms of dominant species composition, Lateolabrax maculatus and Mugil cephalus were the typical dominant species in the surface level of mussel farming habitat, while Nibea albiflora and Sebastiscus marmoratus were the typical dominant species in the bottom level of mussel farming habitat. S. marmoratus was also a typical dominant species in the reef habitat. The similarity analysis showed that the similarity in species composition between the surface and bottom level of mussel farming habitat and the reef habitat was below a moderate level of dissimilarity. Diversity analysis showed that the overall diversity of mussel farming habitat was higher than that of rocky reef habitat, but not significantly (P>0.05). The multivariate analysis indicated that fish community could be grouped into three types in the two habitats, though it was not strictly consistent with the surface area, bottom area and reef area. Results of ANOSIM suggest that there was significant difference among grouped communities (P<0.05). Our study suggests the following: ① the presence of large-scale raft culture facilities in rocky island waters attract many pelagic and demersal fishes, providing additional habitat for dominant rocky fishes, among which S. marmoratus, N. albiflora, M. cephalus and L. maculatus could be suitable target species in the marine ranching programs of northern East China Sea; ② mussel farming habitat and nearshore rocky reef habitat have obvious complementary and gain of habitat functions, which play essential roles on protection of common commercial fish populations in the East China Sea and comprehensive conservation of local fish in different life stages. It is hoped that this study may contribute to technology as well as target fish selection in marine ranching programs and the application of artificial habitat construction model carried out in island waters.