COMMUNITY STRUCTURE OF ICHTHYOPLANKTON IN THE SECTIONS OF THE CENTRAL AND NORTH YELLOW SEA

In order to understand the community structure characteristics of ichthyoplankton at different sections in the coastal waters of the central and north Yellow Sea, three surveys were conducted in May, June and July 2017, the species composition, quantity distribution, and diversity of ichthyoplankton in this sea area were analyzed. The results showed that a total of 5493 fish eggs and 43 larvae were collected during the three surveys by horizontal trawl with plankton net. The obtained ichthyoplankton belonged to 20 species, 20 genera, 16 families, and 7 orders, the main group was perciformes. The number of ichthyoplankton collected varied in different months and there were differences between sections. The collected fish eggs and larvae were mainly composed of warm-temperate species and warm-water species, with only a few cold-temperate species, and the number of species of each ecological type varied with different sections. The T1section was dominated by warm-temperate species, and the T2section had slightly more warm-water species than warm-temperate species, Warm-temperate species showed a decreasing trend from north to south in the surveyed sea area, while warm-water species showed an increasing trend. The composition of dominant and important species in ichthyoplankton changed in different months and sections, Engraulis japonicus is the dominant species of fish eggs in the surveyed waters of the May voyage and sections T1 and T2, and no dominant species appeared in larvae. The average trophic levels of ichthyoplankton collected during the three investigations were 3.58, 3.51 and 3.41, respectively, showing a gradual decrease. The richness index (D), diversity index (H′) and evenness index (J′) of ichthyoplankton were the highest in May and the lowest in June. In addition, there were some differences in the community diversity index of ichthyoplankton between the two sections, which were closely related to the depth.