The community structure of fish larvae and juveniles in the surf zone of the Yangtze River estuary

A total of 49 045 fish larvae and juveniles,representing 84 species from 31 families,were collected monthly on the spring tide at 13 stations in the surf zone of the Yangtze River estuary during July 2006 and June 2007.Samples were collected by a seine net(1 m×4 m,1 mm mesh-aperture) along the surf zone(depth of 0.5-1.5 m).The species composition and community structure of fish larvae and juveniles were studied by cluster analysis and 13 sampling stations were separated into two groups(group A and B).Group A was located in the coastal areas and group B was in the south branch and the upper reaches of the north branch of the Yangtze River estuary.In the whole year,72 species belonged to Group A,mainly including estuary and marine fishes,while 58 species belonged to Group B,which give priority to freshwater and diadromous fishes.The cluster analysis of the 12 months indicated a significant seasonal change in the community structure of fish larvae and juveniles.