Abstract: We analyzed the spatial and temporal variations of fish community structure at the local scale in the waters around Dachen Island, using data of bottom trawl surveys collected from 21 sites in September and November 2020, as well as January and April 2021. A total of 99 fish species were recorded, belonging to 15 orders, 48 families, and 81 genera. 50.51% of those fishes belonged to the order Perciformes. Harpadon nehereus was the most dominant species throughout the year. Amblychaeturichthys hexanema dominated during all seasons except summer. Pampus echinogaster was dominant in summer and autumn. Migratory species such as Muraenesox cinereus, Pennahia macrocephalus, Larimichthys polyactis and Larimichthys crocea dominated in only one season. The results of cluster analysis and nonparametric multidimensional scaling showed two types of fish communities around Dachen Island during summer, autumn, and winter, which were near-estuarine fish communities and open sea fish communities. In spring, fish communities could be grouped into reef island communities and off-island communities, with significant differences in species composition among different groups in each season (P<0.05). Results of redundancy analysis showed that water depth, surface temperature, bottom salinity and bottom temperature were the primary factors affecting fish community structure in this area (P<0.05). Our results indicated significant regional and seasonal variations in the fish communities in the sea area around Dachen Island, and that fish communities were dominated by small-sized and low economic value fish.

Key words: community pattern, Dachen fishing ground, local scale, fish diversity