Species Composition and Diversity of Fish Larvae and Juveniles in the Surf Zone of the Yangtze River Estuary

This study investigated species composition and diversity of fish larvae and juveniles in the surf zone of the Yangtze River estuary to reveal the importance of this habitat as a fish nursery ground. Fish larvae and juveniles were collected monthly at 13 stations on the spring tide during July 2006 and June 2007. Samples were conducted along the surf zone (depth of 0.5-1.5 m) using a seine net (1 m×4 m, 1 mm mesh-aperture). Each haul was made parallel to the shore for a distance of about 50 m. A total of 49 045 fish larvae and juveniles were collected representing 84 species from 31 families. They included 16 marine species, 30 estuarine species, 4 diadromous species and 34 freshwater species. Coilia nasus was the most dominant species accounting for 82.63% of the total. The number of species, individual and abundance were lower in winter with the minimum number in March and maximum in summer. The Margalef index was relatively low between November 2006 and April 2007, the highest being in October 2006. The Shannon-Wiener diversity index was the highest in October 2006 and the lowest in March 2007. The Pielou evenness index was invariable throughout the whole year and relatively low in July 2006 and June 2007.