Species composition and diversity of fish in Dawangtan Reservoir in Nanning, Guangxi

According to the fish resources data collected in Dawangtan Reservoir from November 2016 to August 2017, we investigated the present situation, species composition, dominant species and diversity of wild fish resources in this reservoir. Thirty-four species belonging to 4 orders, 9 families and 26 genera have been identified. Cyprinidae, which accounted for 64.71% of all species and 48.15% of all individuals, was most abundant. According to the analysis of relative importance index (IRI), the most dominant species were Oreochromis niloticus, Cyprinus carpio, Cirrhinus molitorella and O.mossambicus. The Shannon-Wiener species diversity index (H') was 1.213~2.279; the Margalef index (D) was 1.995~3.412; the Pielou evenness index (J') was 0.448~0.771; the Simpson index (C) was 0.120~0.507, which was highest in S3 station but relatively lower in S1 station. The fish species diversity in summer was highest, and that in winter was lowest．Cluster analysis and analysis of similarity (ANOSIM) show no significant difference in the fish communities among seasons and sampling sites. An obvious decreasing trend was found in the number of types of fish resources and the alien species invasion in Dawangtan Reservoir.