Preliminary analysis of nekton composition and diversity in Jiangmen waters, China

Based on four bottom trawl surveys in the Jiangmen waters of Guangdong Province in January (winter), April (spring), August (summer) and October (autumn) of 2016, we analyzed the species composition, stock density, dominant species and biodiversity index in that area. A total of 132 nekton species were captured (94 fishes, 31 crustaceans and 7 cephalopods). The species composition had little difference among seasons. The main species were of Fish, followed by Crustaceans and Cephalopoda. The average annual stock density was 291.61 kg·km^–2, highest in autumn (484.67 kg·km^–2) and lowest in summer (76.76 kg·km^–2). According to the index of relative importance (IRI), the main dominant species were Stolephorus commersoni, Metapenaeus joyneri and Sardinella jussieu, among which S.commersoni was the dominant species of the year. The Margalef species richness index D ranged from 2.325 to 3.029. The Pielou evenness index J' ranged from 0.500 to 0.708. The diversity index H' ranged from 1.201 to 3.032. The results reveal that the catches in this area are mainly small fish, and the individual miniaturization is obvious. The dominant species of Crustacean is single. Compared with the surrounding sea area, the diversity in Jiangmen waters is at middle level.