Species composition and seasonal variation of fish larvae and juveniles in Jiulong River estuary

In order to study the species composition and abundance of fish larvae and juveniles, seasonal collections (9 stations) were conducted with a plankton net (50 cm mouth-diameter, 145 cm net length, 0.505 mm mesh-aperture) in Jiulong River estuary from November of 2007 to August of 2008. Horizontal surface towing and vertical towing were carried out in each station. Middle layer towing was made at station 2. A total of 1 763 fish larvae and juveniles were collected, belonging to 33 species, 16 genus, 15 families. In them, 167 individuals were collected by oblique towing (the average density was 1.97 indm-3), 965 individuals were collected by Horizontal surface towing (the average density was 0.30 indm-3), 631 individuals were collected by a middle layer towing (the average density was 5.39 indm-3). The dominant species were Gobiidae fishes,Acentrogobius pflaumi, Omobranchus elegans, Konosirus punctatus, Engraulis japonicus and Argyrosomus argentatus. The species numbers of fish larvae and juveniles were the greatest in spring (22) and the least in winter (5). Also the average density in spring were the highest in summer and the lowest in autumn andwinter. There were more species and numbers of larvae and juveniles in middle layer than in surface, and there were different distribution of larvae and juveniles in different layers. Compared with the previous researchers, some changes were observed in species composition and the dominant species.