Investigation on the Resources Status of Fish Larvae and Juveniles in Yangtze Estuary Area

The species composition,quantitative distribution,the distribution characteristics of surface water temperature and salinity and their correlation of four cruises of fish larvae and juveniles in Yangtze River estuary water areas from July of 2006 to November of 2007 were investigated.The results showed that there were 22 species of fish larvae and juveniles in this sea area,belonging to 6 orders,7 families and 18 genera.One species was identified to genus level and 2 species were unidentified.Liza haematocheilus was the dominant species in spring,accounting for 77.64% of the total number of fish larvae and juveniles in spring.Coilia mystus was the dominant specie in the summer,accounting for 88.13 % of the total number of fish larvae and juveniles in the summer.Water temperature was one of main causes that affected the distribution of fish larvae and juveniles.Most species of fish larvae and juveniles belonged to euryhaline fish.Compared with the historical data,the species and quantity of economic fish larvae and juveniles dropped.However,the increased percentage of low-value fish larvae and juveniles became the change trend of fish larvae and juveniles resources structure in the survey areas,which showed that economic fish larvae resources of Yangtze River estuary waters were under serious threat.