Relationship between abundance distribution of fish eggs,larvae and juveniles and environmental factors in the Pearl River Estuary waters in spring

Based on data collected from four oceanographic surveys conducted in spring from 2004 to 2007 in the Pearl River Estuary waters,the inter-annual features of fish eggs,larvae and juveniles abundance distribution were investigated,and their relationship with environmental factors was analyzed.The results showed that fish eggs,larvae and juveniles belonged to 9 phyla,33 families,and 58 species.In addition,Perciformes(53.4%) and Clupeiformes(20.7%) were the two most abundant components of eggs,larvae and juveniles.Three ecological groups of eggs,larvae and juveniles were roughly divided into brackish water,near shore and offshore groups.There were 9 dominant species of fish eggs,larvae and juveniles during spring,with 6 dominant species of eggs and 6 dominant species of larvae and juveniles.The adjacent waters of Qingzhou were one of the most important areas for eggs,larvae and juveniles in spring.The annual variations in the abundance of eggs,larvae and juveniles were obvious,with the maximum abundances occurring in 2006.The most important factors influencing the abundance of fish eggs were water temperature,pH and dissolved oxygen concentration,while those influencing the abundance of fish larvae and juveniles were salinity and dissolved oxygen concentration.Salinity,pH,and dissolved oxygen,suspended substances and chlorophyll-a concentration all influenced the number of types of eggs,larvae and juveniles.