Characteristics of fish community structure and its relationship with environmental factors in marine ranching zone in southern area of Yintan in Guangxi

Timely assessment of fish resources in state-level marine ranching demonstration zone is important in promoting the construction of marine ranching. Based on the fishery resources survey data in the southern area of Guangxi Yintan in April 2022, we analyzed the characteristics of fish resources, community stability, fish community structure and their correlation with environmental factors to provide references for research on the ecological effects of marine ranching in Beibu Gulf. The results show that the fish individual density, biomass density and number of species in the demonstration zone were higher than those in the control zone. The fish species composition in the demonstration and control zones was moderately dissimilar at species level. In addition, fish communities in both zones were somewhat disturbed. The fish community in the survey area was divided into four significantly different clusters (p<0.05), which were located in the southern station of the demonstration zone B and the control zone (Cluster I), the northern station of the control zone (Cluster II), the junction of the demonstration zone A and B (Cluster III), and the demonstration zone A (Cluster IV). The average dissimilarity index of Cluster I and III was 53.88%, and the divergent species that ranked in the top three in terms of their contribution were Alepes djedaba, Decapterus marauds and Trachurus japonicus, while the average dissimilarity index of Cluster III and IV was 48.85%, with the top three divergent species (T. japonicus, Leiognathus brevirostri and Saurida undosquamis) contributing to the dissimilarity index. Water temperature and chemical oxygen demand were the main environmental factors significantly influencing the structure of the fish community in the survey area, while dissolved oxygen and phytoplankton density had a slightly weaker effect.