The Categories Composition Of Fish Larvae And Juveniles And Distribution Of Dominant Species In Reproductive Periodin In The Yangtze Estuary

In order to ascertain fish larvae species composition and community structure, and environmental factors on fish larvae distribution area and density of the Yangtze River Estuary. In the study, we investigate the Yangtze River estuary and its adjacent waters areas at 23 stations,used bottom trawlers ship to carry out. Carry out the survey strictly according to the standard to. Our study used plankton net to trawling in horizontal at every station. Every station we use 2 nmile?h-1 to trawl 10 minutes. Flood tide and edd tide each sampling time, and save with 95% alcohol for a further study of molecular analysis.Determination of data(Temperature, salinity and dissolved oxygen) for each site by water quality analyzer(YSI Pro plus). We use ADCP and current meter to measure the depth and velocity. We use microscope to observe the morphology and measure body length of the fish larvae collected at different station. And also use the technology based on DNA barcode sequences of mitochondrial COI to identify fish larvae species. 1. The community structure characteristics of fish larvae and species composition monthly variation at Yangtze River Estuary.survey collected 11 orders, 14 families, 29 kinds of fish larvae, including 13 species Perciformes and 6 species Cypriniformes. We collected 4 orders, 7 families and 7 species fish larvae in April, 5 orders, 7 families and 10 species fish larvae in May, 9 orders, 12 families and 21 species fish larvae in June. The turnover rates of fish larvae in April to June above 60%. This indicates that there is a significant change of fish larvae species. The dominant species of April and May is Liza haematocheila and Repomucenus olidus. Diversity analysis showed: there was no significant difference in richness and evenness index in the 3 month, the diversity index of June was significantly higher than in April and May and there was no significant difference between April and May. Fish larvae were encountered four ecological model, and there are some differences in the composition of ecotype every month. Data demonstrate Hemiculter bleekeri spring start spawning more types of freshwater spawning type spring has begun, but a small number. The types and sites cluster analysis showed that at the 30% level can be divided into three groups, respectively, in April Liza haematocheila dominant species represented in brackish taxa; in May dominant species represented Repomucenus olidus brackish species groups; relative to June dominant species Hemiculter bleekeri as the representative of the freshwater type groups.In conclusion, the species composition, distribution, dominant species, ecological types, diversity and community structure were differences in Spring.2.The fish larvae species composition and distribution characteristics of Yangtze River estuary and its adjacent waters area,By analyzing the composition and distribution characteristics of fish larvae species in May and June high tide and ebb, we found that: There appeared 10 species fish larvae in May, including six kinds of high tide, nine kinds ebb, and 5 species in the same. Tide dominant species in Hong ramp, no dominant species in ebb, and ebb relatively dominant species more than two kinds of high tide. Distribution of high tide and ebb is not very different, but the tide ebb significantly higher density. There appeared 21 species fish larvae in June, including 19 kinds of high tide, 10 kinds ebb, and there was no ebb dominant species and 4 comparative species in the same in June. High tide density and distribution are greater than ebb. There is a certain impact on the regional distribution and distribution of fish larvae with the tide change.3.The dominant species distributions were compared among tides and Relationship with salinityBy analyzing and comparing the distribution and density of Liza haematocheila from April to June in the flood and ebb tides shows that, Liza haematocheila are mainly distributed in the North Branch of Yangtze River Estuary in April, the density and range in the edd tide are high than flood。the distribution of Lophiogobius ocellicaudaalso had the same phenomenon as Liza haematocheila that the edd tide is high than flood tide in May. But Repomucenus olidus in May and Hemiculter bleekeri in June on the opposite of Lophiogobius ocellicauda. The results showed that the distribution of the tide will produce different effects on different types of fish larvae and juveniles, but the extent and scope of the specific impact of the need for further research to prove. The study also showed that from April- June in spring the range of low salinity expanding and the estuary area of freshwater punch role mainly in the waters of the Yangtze River mouth east section is closely related to freshwater species emergence and role of the Yangtze River diluted water.