Spatial And Temporal Distribution Of Nekton Community Structure And Biodiversity In The Yellow Sea And The Northern East China Sea

The nekton community is an important part of the marine biological community.It provided a large number of high-quality proteins for humans.It played a very important role in maintaining the balance of the marine ecosystem and ensuring the food supply.However,under the multiple pressures of overfishing,environmental pollution,reclamation,climate warming and seawater acidification,the biological community structure of the Yellow Sea and the northern East China Sea had changed.It was great significance for the development,utilization and protection of nekton resources to grasp the spatial and temporal distribution of the community structure and diversity of nektons in this area,and to understand its status and changing laws.In this paper,the main lines of the structure and diversity of the group roads in the Yellow Sea and the northern East China Sea were combined.Based on the characteristics of the bottom trawl survey data in the Yellow Sea and the Northern East China Sea,the different spatial interpolation methods to the community diversity was compared in this area.According to the results of this study,the spatial distribution map of species diversity was drawn,and then the composition and diversity of nekton community structure were analyzed from the perspective of seasons and space.The main results were as follows:Took the diversity of nekton in the Yellow Sea and northern East China Sea in May2017 as an example,the species number(S),Shannon-Weaver diversity index(H'),Pielou evenness index(J),and Margalef richness index(d)were selected to evaluate the distribution of species diversity in the sea area.We applied inverse distance weighted(IDW),radial basis function(RBF),local polynomial interpolation(LPI),ordinary kriging(OK),and ordinary cokriging(COK)methods to the above four species diversity indices,and we selected the spatial interpolation method suitable for each species diversity index by the jackknife method.The results showed that the predicted value of COK and the sample value R~2 is the largest,MAE and RMSE are the smallest,indicated that COK had the best results for the four species diversity indices with the highest accuracy.The accuracy of the other four methods had little difference and was low.The size distribution of the four diversity indices at the sample points is basically consistent with the spatial distribution predicted by COK,so COK can be used as a spatial interpolation method for the diversity of nektons in the Yellow Sea and the northern East China Sea.Based on the survey data of fishery resources in the Yellow Sea and the North Sea in the spring(May),summer(August),autumn(October),and winter(January)2017,the status of temporal and spatial changes of the community structure and species diversity of nektons were analyzed by methods including cluster analysis,non-metric multi-dimensional scaling and analysis of similarity and so on.The results showed that:in the four seasons of 2017,265 species of nektons,131 families and 187 genera were identified in the Yellow Sea and the northern waters of the East China Sea.Among them,the number of fish species was the largest,with 176 species in 130 genera and 88 families,accounting for 66.4%of the total species;followed by crustaceans,there were 74 species in 50 genera and 38 families,accounting for 27.9%of the total species;cephalopods were the least,There are 9 families,11 genera and 18 species,accounting for 6.8%of the total species.The cluster analysis results showed that at a 50%similarity level,the species composition of nektons in the Yellow Sea and the northern East China Sea could be divided into three groups.group A:spring,winter in the Northern East China Sea and spring,summer,autumn,and winter in the southern Yellow Sea.;Group B:summer and autumn in the northern East China Sea;Group C:spring,summer,autumn and winter in the northern Yellow Sea.Group B and Group C with the largest geographical distances had the largest average dissimilarity(69.67%),and the average dissimilarity between groups adjacent to each other is less than 55%.In the analysis of the similarity of nekton communities,it was found that many of the nektons that contributed more to the average similarity in the group C were cold temperature types,and contributed more to the average similarity in the groups A and B.Almost all nektons were warm temperature and warm water types.The biodiversity indexes were changing in season and space.The mainly reason was the migration of fish.In the warm half of the year,the Yellow Sea cold water mass had a greater impact on community diversity.There were seasonal differences in the diversity of the Yangtze Estuary nekton community.The reason might be that the sea area of the Yangtze River estuary was affected by fresh water,which lead to unstable environmental conditions in the nearby sea area and high sea water turbidity,which was not conducive to biological life.However,in the autumn,organisms would migrate to the sea area for bait.And winter was the dry season of the Yangtze River.At this time,the runoff of the Yangtze River would decrease.Then the impact of flushing water on the netkon community in the sea area would be reduced.Therefore,the species diversity index higher in autumn and winter than in spring and summer.