Abstract:

To evaluate the fish assemblages of Yangtze Riverconnected lakes, spatial and temporal variations of fish assemblages in the littoral zone and open water of the Poyanghu Lake in the middle and lower basin of the Yangtze River were investigated seasonally from April to November 2010. Throughout the study, 72 species belonging to 7 orders, 14 families and 46 genera were collected. Lake resident species was the richest, accounting for 5556% of total fish species. Riverlake migratory species accounted for 2500% of total fish species. While riverine species was the least, accounting for 1944% of total species. We collected a total of 6 136 individuals, representing 49 species, with 10 species such as Carassius auratus, Cyprinus carpio, Silurus asotus, Pelteobagrus fulvidraco as the dominant species in the littoral zones. We collected a total of 6 136 individuals, representing 68 species, with 10 species such as Coilia ectenes, Carassius auratus, Hemiculter bleekeri, Pseudobrama simoni as the dominant species in the offshore areas. Fish density and biomass differed significantly among the sampling sites in littoral zone, while fish species richness and biomass differed significantly among the sampling seasons in open waters. As observed for littoral zone samples, fish density was the highest in W3 and the lowest in W4, fish biomass was the highest in W3 and the lowest in W5. As observed for open water samples, fish species richness was the highest in September and the lowest in April, fish biomass was the highest in November and the lowest in April. Associations between fish abundance and environmental variables were examined with canonical correspondence analysis, which is a weighted averaging method that directly relates assemblage data to environmental variables by constraining species ordination to a pattern that correlates maximally with environmental variables. Correlations between environmental variables and canonical correspondence analysis axes were used to assess each variables contribution. In the littoral zones, speciesenvironment correlation coeffcients for the first four pairs of axes (CCA 1-4) were 0853, 0789, 0781, and 0859, respectively. For the first four assemblage axes, cumulative percent variance of species data was 29%. In the open water, speciesenvironment correlation coeffcients for the first four pairs of axes (CCA 1-4) were 0864, 0. 0875, 0000, and 0000, respectively. For the first four assemblage axes, cumulative percent variance of species data was 55%. Canonical correspondence analysis indicated that the environmental factors shaping fish assemblages were different between the two zones: water temperature, tributary presence/absence, distance from main channel of Yangtze River and water transparency were the significant environmental factors in the littoral zones; while distance from main channel of the Yangtze River and water transparency were in the open water