The continuous observation of ichthyoplankton species composition and diversity in summer in Yangtze River estuary

To clarify the relationship between species composition of ichthyoplankton and tides in the Yangtze River estuary,we set 2 survey stations,L1 and L4,respectively on July,2017.The sample was collected continuously for 24 hours.A total of 19 fish eggs and 201 juveniles were collected at the L1 station and a total of 17 fish eggs and 92 juveniles were collected at the L4 station.We totally obtained 70 mtCOI.Sequences of 26 species were identified,of which 19 were identified to the species level,1 was identified to the genus level,and 6 were identified to the level of the genus.The average genetic distance within the species is 0.007.The results of species diversity analysis based on the DNA barcode showed that:there were 14 species at L1 station and 21 species at L4 station.Tide had a great influence on the abundance of ichthyoplankton in the Yangtze estuary,but had little to do with species composition.The abundance of inshore station decreased at flood tide and so did that of offshore station.Inshore station had higher abundance than off-shore station,but offshore station had higher species richness.The results showed the reliability of DNA barcode technology in the study of fish eggs and larvae diversity,and revealed the influence of tidal waves on the species composition of fish eggs and larvae in the Yangtze River estuary.