Study On Community Structure And Biodiversity Of Nekton In The Conservation Zone Of Spawning Ground For Wen-tai Fishing Ground And Nearby Waters

Based on the data from fishery resources survey carried out in the conservation zone of spawning ground for Wen-tai fishing ground and nearby waters in spring 2018,autumn2018,spring 2019 and autumn 2019,this paper used relative importance index,niche determination,species diversity index,ABC curve,cluster analysis,species replacement rate and functional group analysis to study the community structure and biodiversity of nekton in the sea area.A total of 103 species of nekton were captured in 4 voyages.65,65,42 and 54 species of nekton were captured successively in spring 2018,autumn 2018,spring 2019 and autumn 2019.The 4 voyages of nekton are mainly warm-water species and warm-temperature species,and few cold-temperature species.From 2018 to 2019,the total mantissa and total weight of nekton in autumn were much higher than that in spring,and the fishs was the first in the the total mantissa and total weight of four voyages,and the crabs was the second.According to the IRI index,the 4 voyages had the dominant species of2,5,5,and 3 in turn,the important species of 9,7,8,and 7 in turn.Harpodon nehereus,Portunus trituberculatus,Oratosquilla oratoria and Charybdis japonica were the dominant species or important species in four voyages,and the average replacement rate of the dominant species and important species in four voyages were 72.07%.The results of species diversity index in 4 voyages showed that the diversity level of the nekton community in the sea area were low.The results of cluster analysis showed that20 stations on 4 voyages can be divided into 3 groups,3 groups,3 groups,and 4 groups in turn,and the stations near the western islands and the stations on the far east coast will not be classified into one group basically.The results of ABC curves showed that the community of nekton in the sea area were moderately disturbed during the 4 voyages.The variation range of the niche width of dominant nekton in 4 voyages was 0.78-4.05,0.68-6.76,0.96-4.87 and 0.20-6.66 respectively.According to the results of niche width cluster analysis and the current situation of niche width,the dominant nekton in the 4voyages were divided into three categories:narrow niche species,middle niche species and wide niche species.The range of niche overlap values of dominant nekton in 4 voyages was0-0.89,0.02-0.94,0.02-0.91 and 0.05-0.87 respectively.The species pairs with O_ik?0.6accounted for 25.45%,39.39%,42.22%and 44.44%of the total species pairs of each voyages in turn.From 2018 to 2019,the niche width and the niche overlap of the dominant nekton in autumn was slightly higher than that in spring.Based on the analysis of the relationship between niche breadth value and niche overlap value in four voyages,it is found that there was no positive correlation between them.According to the feeding habits of the dominant nekton and the relevant literature,24kinds of dominant nekton were divided into 6 functional groups.There were 4,4,5 and 4functional groups in the four voyages in turn,among which,the zoobenthos/nekton feeding function group in the 4 voyages was absolutely dominant.The regression analysis of species diversity and functional group diversity of main nekton in each station of 4 voyages showed that there was a positive correlation between them.