| The data used in this paper were collected from the trawl survey of fishery resources in the coastal waters of Zhoushan Islands in 2007 and 2015-2016.The species composition and community structure characteristics of fish in the coastal waters of Zhoushan Islands were studied by using the relative importance index IRI,CLUSTER cluster analysis,ABC curve,ANOSIM test,NMDS analysis and SIMPER analysis.Compared with the two different years,it was found that :(1)A total of 47 species of fish were obtained in 2007,including 29 species in spring and 35 species in autumn;A total of 50 species of fish were obtained from 2015 to 2016,including 26 species in spring and 37 species in autumn;The total number of species in the October slightly increased compared with that in the 2007,the number of species in the spring slightly decreased compared with that in the spring of the 2007,and the number of species in the autumn slightly increased compared with that in the autumn of the 2007.The species similarity index values between years and in the same season were less than 30 %,indicating that the composition of fish species in these two years and in the same season had significant changes,which were extremely dissimilar.Compared with the 2007,the number of anchovy fish species increased significantly in the 2015-2016,the number of Megalobrama amblycephala and Caryophyllidae fish species decreased significantly in the 2015-2016,and the number of tongue sole and shrimp tiger fish species changed little.(2)By comparison,the inter-annual variation of dominant species was significant,and the first dominant species was the same in the same quarter.The dominant species in spring of 2016 and 2007 were Amblychaeturichthys hexanema,Collichthys lucidus,Sebastiscus marmoratus and Amblychaeturichthys hexanema,Larimichthys polyactis,respectively.The dominant species in autumn of 2015 and 2007 were Harpodon nehereus and Harpodon nehereus,Sardinella nymphaea,respectively,with significant changes in dominant species.(3)The coastal waters of Zhoushan Archipelago are dominated by warm-water and warm-warm fish,and the proportion of cold-water fish is relatively small;Compared with the 2007,the proportion of warm water species increased in the2015-2016,and the proportion of warm water species decreased.The number of warm water species in the 2007 was greater than that of warm water species,and the number of warm water species in the 2015-2016 was greater than that of warm water species in the 2007.(4)The weight density and tail number density of fish in the spring of the October were much lower than those in the spring of the 2007,and the weight density in the autumn of the October was slightly lower than that in the autumn of the 2007,and the tail number density was significantly increased.In the spring and autumn of the 2007,the fish weight density and tail density were higher in the sea area near Shengshan.In the spring of the 2015-2016,the fish weight density and tail density were higher in the sea area near the East Pole and the southern sea area of Shengshan.In the autumn of the2015-2016,the fish weight density was lower in the sea area near the East Pole,and the distribution of other sea areas was relatively uniform.The tail density was evenly distributed in the survey sea area.(5)The fish communities in the spring and autumn of the 2007 can be divided into 3 and 4 groups,respectively,and the fish communities in the spring and autumn of the 2015-2016 can be divided into 3 groups,with significant inter-annual group changes.SIMPER analysis showed that most of the intra-group characteristic species and inter-group divergence species in each season were the dominant species and important species in this season,and the inter-annual intra-group characteristic species and inter-group divergence species changed greatly.ANOSIM test showed that there were significant differences in seasonal communities between the spring of the 2007 and the spring of the 2015-2016,the autumn of the 2007 and the autumn of the 2015-2016.ABC curve analysis showed that the fish community was seriously disturbed in the spring and autumn of the 2007 and 2015-2016,and the fish community was relatively stable in the autumn of the2007.(6)The richness index(D)in the spring and autumn of the 2015-2016 was greater than that in the spring and autumn of the 2007,and the maximum value of the richness index(D)in the spring and autumn of the 2015-2016 was greater than that in the spring and autumn of the 2007.The evenness index(J’)and diversity index(H’)in the spring and autumn of the October were smaller than those in the spring and autumn of the 2007;In the spring and autumn of the 2007,the biodiversity of the sea area near Shengsi and the sea area near the East Pole were higher.Compared with the spring and autumn of the 2007,the spring and autumn of the 2015-2016 were also lower near the Hangzhou Bay,but the distribution in other sea areas was relatively uniform.In the two years,the biodiversity of the sea area near the islands was higher,and the fish diversity in the water depth greater than 20 m was higher. |
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