Abstract:To make a further clarification of the seasonal dynamics of species composition and abundance distribution of fish larvae and juveniles in the surf zone of the Yangtze River estuary, fish larvae and juveniles were collected at 13 stations by a seine net (1 m ×4 m, 1 mm mesh aperture) monthly from November 2006 to October 2007. There were 77 species of fish larvae and juveniles belonging to 63 genera in 27 families of 13 orders, in which Perciformes and Cypriniformes were the dominant families. The number of species collected in summer,spring,autumn and winter was 37, 20, 13 and 7 respectively. In all seasons, the warm temperate species were absolutely dominant. In terms of the ecological types, the number of estuarine species was as much as that of freshwater species, followed by marine fish, and diadromous species was the least in ecological types. By analyzing the dominance curve of fish larvae and juveniles, we found that the dominance of species was the most prominent in summer, while not obvious in autumn. The shared species in different seasons showed more conformity between summer and autumn, but more difference between winter and other seasons. Catches varied significantly among seasons, peaking in summer with a mean of 1 132 ind./station. The abundance of fish larvae and juveniles was the least and the distribution was the most dispersive in winter, and increased dramatically in spring, then became more abundant and more concentrated in summer. The average density reached 2 729 ind./station, mainly composed of Coilia nasus, at the freshwater or low salinity area of St.4, St.5, St.7 and St.10.
