ANALYSIS OF MOLLUSCS COMMUNITY STRUCTURE IN THE ZHEJIANG COAST

Based on survey data collected in 4 seasons of 2019 by single bottom trawling of Zhejiang surrounding waters, the paper analysed species composition, dominant species and the distribution of resources density of molluscs. Ecosystem diversity index, Species similarity index (J_s), Alternate index (AI), Migration index (MI) and abundance/biomass comparison curve (ABC curve) were adopted to analyse species diversity of community and its dynamic changes. The results showed that 62 molluscs species were captured belonging to 3 classes 10 orders, and 32 families, and the dominant species were Octopus variabilis, Loligo edulis, Turritella bacillum, Abralia multihamatai, and Sepiola birostrata all the year. The seasonal variation of dominant species was quite different. The annual average resource density was 204.94 kg/km², The resource density in summer was the highest value in the whole year, and Winter was the lowest. The average resource density was increasing gradually from north to south roughly. The annual average values of species abundance index (D), species diversity index (H′) and species evenness index (J′) were 0.70, 0.88 and 0.61 respectively. Three indices values indicated that molluscs community diversity was on a low level. The values of Species similarity index (J_s), Alternate index (AI) and Migration index (MI) indicated that the community stability was higher in spring and winter than in summer and autumn. According to the ABC curve, molluscs community all the year were moderately disturbed respectively.