For studying the fish community characteristics influenced by the habitat variation in Yangtze River Estuary,which could be used to determine how to manage its fish resources usefully,fishes from Yangtze River Estuary were collected during summer(the second half month of May to August 2010)and autumn(September 2010)every week(every half a month in the first half of August).During the study periods,39 species belonging to 6 fish ecological guilds and 20 families,12 orders were identified,most of them were marine migrant fishes (17 species) and estuarine resident species(14 species),and Engraulidae had the highest numbers of fishes(6 species),then followed by Gobiidae and Sciaenidae(4 species).Cochran and Friedman test was used to indicate that species composition or numbers of each guild in each month between May and September had no significant difference,respectively.Marine migrant taxa were both the most important guild of abundance or catch in each month,and average abundance or catch per net showed no statistical variations between May and August,but it was higher in September than that from May to August(except average abundance in July).Significant difference occurred in abundance or catch rank in each guild.Percentages of juveniles of 6 importantly commercial species(Big head croaker Collichthys lucidus,Japanese grenadier anchovy Coilia nasus,Osbeck’s grenadier anchovy Coilia mystus,silver pomfret Pampus argenteus, dark pomfret Pampus cinereus, and Bombay duck Harpodon nehereus) were examined to exhibit the variability in rank-distributions,C.lucidus and C.nasus declined,by contrast,C.mystus increased,P.argenteusoccured from May to August,while P.cinereus was observed during August to September. C.nasus spawn in fresh water,but C.mystus breed in the Estuary,which would reflect the temporal or spatial segregation of species of fishes belonging the same genus and were considered the ecological lysimilar,impling that they may reduce the competition for food or space during peak recruitment.According to the synthetic abundance method,dominant species dominated more than 95% of synthetic abundance,but no significant difference was observed among dominant species composition in each month.In addition,cluster analysis and non-metric multi-dimension scaling plot ordination of Bray-curtis similarity method based on abundance and catch showed that community could be divided into 2 groups on 60% similarity level,group Ⅰ consists of samples between May and the first half month of August,while group Ⅱ consists of fishes from the second half month of August to September.When compared with the previous study,although Yangtze River has still been the nursery and feeding ground for importantly commercial fishes,community structure has varied,and the major difference that could be observed is that the absence of rare species such as hilsa herring Macrura reevesii, Chinese sturgeon Acipenser sinensis.The study might reflect the degradation of fish resources due to overfishing,water pollution and large-scale hydrological project construction.