乐清湾春、秋季游泳动物群落结构特征及与环境因子关系研究OA

Two trawl fishing surveys were conducted to reveal the community structure,biomass,and biodiversity of nekton in the Yueqing Bay in the southern Zhejiang in November,2021(autumn)and May,2022(spring).The cluster analysis,non-metric multidimensional scaling,and redundancy analysis were used to study the relationship between community structure and environmental factors.79 species belonging to 14 orders,40 families,and 62 genera were identified in the two surveys,including 47 fish species and 32 crustacean species.47 species were identified in spring survey and 40 species were identified in autumn survey.Portunus trituberculatus,Collichthys lucidus and Harpodon nehereus were the dominant species in spring survey while Portunus trituberculatus,Harpodon nehereus and Charybdis japonica were the dominant species in autumn.Compared with the survey data in the 1960s and 1970s,the dominant species had evolved from high-value economic species to small,low-value fish.The resource densities of nekton biomass and individual were 1.32×103 kg·km-2 and 75.02×103 ind·km-2 in spring.From a spatial perspective,the biomass and individual resource densities were the highest in the middle bay.The resource densities of nekton biomass and individual were 1.34×103 kg·km-2 and 66.29×103 ind·km-2 in autumn.From a spatial perspective,the biomass and individual resource densities were the highest outside the bay.The individual resource density in spring was slightly higher than that in autumn,and the biomass resource density was roughly the same.The diversity index(H'),evenness index(J'),and richness index(D)in autumn were higher than those in spring,and there were significant differences in the diversity index and evenness index between spring and autumn(P<0.05).As the RDA analysis shown,depth and dissolved oxygen were the main environmental factors on the variation of community structure of nekton in the Yueqing Bay,and the correlations varied with seasons.In spring,Portunus trituberculatus,Collichthys lucidus,Harpodon nehereus,Charybdis japonica,and Coilia nasus were positively correlated with dissolved oxygen.while in autumn,Collichthys lucidus,Harpodon nehereus and Coilia nasus were negatively correlated with dissolved oxygen.The research can provide basic information for understanding the current status of fishery resources in the Yueqing Bay,with a view to providing scientific basis for the formulation of relevant fishery resource management measures.