The Ecological Study For Fish Community In The East China Sea Continental Shelf: The Spatial Pattern And Diversity

the spatial patterns and diversity characteristics of the fish community, based on the data from bottom trawl fisheries resources survey (1997~2000) within 26°00'~33°00'N, 120°30'~128o00'E (30~200m) in the East China Sea continental shelf, were analyzed in some different degrees by some mathematical methods such as non-parametric estimator, geostatistics, multivariate analysis, K-dominance curves, Hill's diversity index family and taxonomic diversity measures, and the persistence, change and uncertainty of the fish community, the effect of environmental factors on the fish community also were discussed in a larger spatial scale.Firstly the fish species richness was estimated and its spatial distribution pattern about the fish community was analyzed. Three hundred and fifty fish species were collected during the survey, belonging to 236 genera, 120 families, 29 orders and 3 classes. The fish species richness was between 393 and 483 esteimated by non-parametric estimator, such as Chao2, Jackknifel, Jackknife2 and Bootstrap methods, but the fish species richness estimates of single cruise was estimated relatively low. The spatial distributions of fish species richness were same for all seasons, where species richness mapping showed spatial gradients by geostatistics. The exponential models in spring, summer and autumn and the spherical model in winter successfully explained the spatial autocorrelations of the fish species richness. The fish species richness increased along the depth gradients, whereas it was not obviously changed along the latitude gradients.Secondly the spatial structures of the fish community were studied by using the cluster analysis and non-metric multidimensional scaling (NMDS). The result showed that three fish community styles were identified. To test the null hypothesis that fish communities did not differ in structure, a one-way ANOSIM procedure was used. The changes of fish community structure were obvious along the depth gradients. Each fish species inhabits within certain depth ranges. Different currents had different characters of temperature and salinity which affect the distribution and migration rule, consequently, the species composition was controlled. Among these communities, the spatial character and species composition kept relative stability in all survey for theout edge of continental shelf community. Whereas their boundary disappeared in the summer, and maintained in other seasons for the coastal fish community and mixed fish community. The species only belong to single community are few. The depth ranges of all fish species' occurrence overlapped, but the biomass and occurrence of the species varied significantly with depth. They appeared to have different depths where they reach their maximum biomass. Moreover, these fish species needed different marine environment in life history, so that they immigrated to the continental shelf area in order to search the optimal marine environment. On this account the definition for three communities is relative, it is very difficult to determine the permanent geographic area of fish community. The boundary between fish communities changes with different seasons.The main characters for three fish communities in the continental shelf could be described respectively as follows:(1) Coastal communityThis type of community mainly distributes in the coastal sea of the northern and mid-southern East China Sea, which sites at depth <60m with lower salinity, wide range of water temperature.Major species of the community were the estuarine resident fishes including Coilia ectenes Jordan et Seale, 1905, Coilia mystus (Linnaeus, 1758); the coastal marine fishes including Harpadon nehereus (Hamilton, 1822), Setipinna taty (Cuvier et Valenciennes, 1848), Thryssa kammalensis (Bleeker, 1849), Collichthys lucidus (Richardson, 1844), Collichthys niveatus Jordan et Starks, 1906, and Eupleurogrammus muticus (Gray, 1831). Some marine migrant fish, including Larimichthys polyactis (Bleeker, 1877), Pampus argenteus (Euphrasen, 1788), Argyrosomus argentatus (Houtt...