Abstract: The North Creek Basin of the Jiulong River is located in a typical subtropical monsoon climate zone, characterized by distinct hydrological seasonality. However, systematic research on the temporal and spatial variations of its fish community structure and the underlying driving mechanisms remains lacking. To understand spatiotemporal patterns of fish communities and the driving factors in the North Creek Basin of the Jiulong River, we examined fish communities from 18 sampling sites in March (spring, the dry season) and September (autumn, the wet season) of 2021. A total of 58 fish species, belonging to 49 genera, 16 families and 4 orders, were collected throughout the year. The majority of the specimens were cyprinids, followed by flathead loaches and gobies. The dominant species in the dry season included Coptodon zillii, Rhinogobius giurinus, and Oreochromis niloticus. The dominant species were C. zillii and O. niloticus in the wet season. Species richness and Shannon index were significantly lower in the dry season than those in the wet season. Spatially, fish abundance in the mainstem was significantly lower than that in the tributaries. Redundancy analysis results indicated that water depth and dissolved oxygen were the key environmental factors influencing fish abundance and biomass patterns during the dry season. During the wet season, water temperature, dissolved oxygen, and permanganate index were the key factors affecting fish abundance and biomass patterns. This study revealed the spatiotemporal patterns and influencing factors of fish communities in the North Creek Basin, providing a scientific basis for fish diversity conservation and ecosystem health maintenance in subtropical rivers.

Key words: river, fish, community structure, spatiotemporal pattern, dam