The spatial pattern of the small fish community in the Biandantang Lake - a small shallow lake along the middle reach of the Yangtze River, China

The spatial pattern of the small fish community was studied seasonally in 1 996 in the Biandantang Lake. Based on plant cover, the lake was divided int o five habitats, arranged in the order by plant structure complexity from c omplex to simple: Vallisneria spiralis habitat (V habitat), Vallisneria spi ralis-Myriophyllum spicatum habitat (V-M habitat), Myriophyllum spicatum ha bitat (M habitat), Nelunbo nucefera habitat (N habitat), and no vegetation habitat (NV habitat). A modified popnet was used for quantitative sampling of small fishes. A total of 16 fish species were collected; Hypseleotris sw inhonis, Ctenogobius giurinus, Pseudorasbora parva, Carassius auratus and P aracheilognathus imberis were the five numerically dominant species. In bot h summer and autumn, the total density of small fishes was about 10 ind m(- 2). Generally, Ctenogobius giurinus, a sedatory, benthic fish, was distribu ted more or less evenly among the five habitats, while the other four speci es had lower densities in the N habitat and NV habitat, which had the simpl est structures. The distribution of the small fish species showed seasonal variations. In winter, most species concentrated in the V habitat, which ha d the most complex structure. In spring, the fish had low densities in the N and NV habitat, and were more or less evenly distributed in the other hab itats. In summer, the fish had a low density in the NV habitat, and were ev enly distributed in the other habitats. In autumn, the fish had higher dens ities in the V-M and M habitats than in the others. Generally, spatial over laps between the dominant species were higher in winter than in the other s easons. It was suggested that the variations in the importance of predation risk and resource competition in habitat choice determined the seasonal ch anges of spatial patterns in the small fishes in the Biandantang Lake.