| The structures of fish egg,larva and juvenile communities were discussed based on fish egg,larva and juvenile data and environmental factor data collected in 4 surveys conducted from November 2017 to July 2018 respectively.The change rules and influencing factors of the community structures were analyzed,providing reasonable suggestions for the sustainable development of fishery resources in Daya Bay.Our main research results are as follow:1.According to the database comparison results combining with the phylogenic trees and the the value of K2P distance,a total of 136 fish egg,larva and juvenile species were identified in Daya Bay,and we described their morphologies.Among them,110 species were identified to the level of species,20 to the level of genus,3 to the level of family,and 3 species were not identified due to database limitations.The average intraspecific distances were between 0 and 0.011,and the minimum multiple of the average interspecific and intraspecific distance was 14 times,which conforms to Herbert’s 10× rule,indicating that DNA barcoding can be applied to the identification of fish eggs,larvae and juveniles.2.Except for the 3 species that were unidentified,all species belonged to 10 orders,45 families and 96 genera.Among them,Perciformes accounted for the largest proportion,with 85 species;Pleuronectiformes came next,with 15 species;Clupeiformes has the third most species number,with 14 species.Wthin all families,Gobiidae had the maximum number of species,with 11 species;Engraulidae,Sparidae,Sciaenidae,Cynoglossidae shared the second highest number of species,all was 8.3.A total of 31190 fish eggs and 2786 larvae and juveniles were caught during the 4 voyages.Among them,Clupeidae had the most quantity.The abundance,species number and diversity of spring were the highest in all 4 seasons,indicating spring was the main breeding season of fishes in Daya Bay.The abundance,species number and diversity of fish eggs were also high in summer,but the diversity index of larvae and juveniles was much lower than that of spring.The abundance,species and diversity of fish eggs,larvae and juveniles in autumn and winter were significantly less than those in spring and summer.4.The species of fish eggs,larvae and juveniles in Daya Bay varied significantly between 4 seasons.The first dominant species of fish eggs was Sillago sihama in autumn,while that of fish larvae and juveniles was Bregmaceros sp.1;The first dominant species of fish eggs was Acanthopagrus schlegelii in winter;The first dominant species of fish eggs was Nuchequula nuchalis in spring,while that of fish larvae and juveniles was Sardinella jussieu;The first dominant species of fish eggs,larvae and juvenile were both Sardinella jussieu.The species replacement rates of the 4 seasons were 98%,94.39%and 67.26%,respectively.5.The results of Cluster analysis and NMDS showed that the clustering of fish eggs was obvious in all seasons,while larvae and juveniles was not.The fish egg stations in spring were divided into along-coast assemblage,the mid-out bay assemblage and 2 single stations;in summer,they were divided into along-coast assemblage and mid-out bay assemblage;in autumn,they were divided into outer-bay assemblage and inner-bay assemblage;in winter,they were divided into inner-bay assemblage,bay-mouth assemblage and random assemblage that contained Callionymus curvicornis only.According to Pearson correlation analysis of diversity indexs and environmental factors,species number and richness of fish eggs were correlated with surface chlorophyll a and surface dissolved oxygen,while abundance,species number and richness of larvae and juveniles were significantly correlated with surface temperature and surface chlorophyll a. |
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