Abstract: Autumn fishery by enclosing plate-shaped sub-lake is an extensive fishing method around the Poyang Lake, which is influenced by the hydrological changes and has a certain negative impact on fishery resources. In order to research the composition and characteristic dynamics of fish community in the sub-lake, and observe the correlation between the catch and water level changes, an investigation was carried out for three times in Dahuchi and Shahu located in Poyang Lake National Nature Reserve, Jiangxi province, China, from 2011 to 2013. The study was conducted in aspects of catch species diversity and the relation between its yield of commercial fishes and water level changes to describe the true situation and its change features and probable problems. The connection time of Dahuchi and Shahu with Xiu River in 2011 were 23 days and 10 days respectively, and a phenomenon of drought-flood abrupt alternation occurred in Poyang Lake. Poyang Lake had a flood year in 2012, and the connection time of Dahuchi and Shahu with Xiu River were 124 days and 108 days respectively. While Poyang Lake suffered a drought year again in 2013, and both lakes did not connected with the river. 7 times inquiries were implemented in two lakes in 2011, 9 times in 2012 and 5 times in 2013. In this study, totally 59 fish species were collected, belonging to 6 orders, 12 families and 43 genera. In 2011, totally 41 fish species were collected, belonging to 6 orders, 10 families and 34 genera, and 38 species in Dahuchi, belonging to 6 orders, 10 families and 31 genera, and 32 species in Shahu, belonging to 6 orders, 7 families and 27 genera, six of them were commercial fishes. In 2012, totally 49 fish species were collected, belonging to 6 orders, 10 families, 35 genera, and 44 species in Dahuchi, belonging to 6 orders, 10 families, 32 genera, and 36 species in Shahu, belonging to 6 orders, 8 families, 27 genera, 8 of them were commercial fishes. In 2013, totally 38 fish species were collected in Dahuchi, belonging to 6 orders, 10 families, 32 genera, 7 of them were commercial fishes, and there was no fisheries production in Shahu because of the low water level. The results of the investigation study showed that the largest group was from Cypriniformes, and had the similar fish species in different years, but the dominant species were changed and the yield of catch had a downward trend. The analysis of non-metrimultidimensional scaling (MDS) showed that community diversity varied among years and sub-lakes. The correlation analysis indicated that there was a positive correlation between CPUE a day and the water level in the year of 2011, while such correlation declined in the year of 2012 and 2013.

Key words: Poyang Lake, Sublake, fish resource, water level