Temporal and spatial variation of fish assemblages in Dianshan Lake,Shanghai, China

Using multi-mesh gillnets and trawls, the fish communities in Dianshan Lake at 6 stations from Oct. 2009 to Jul. 2010 were investigated seasonally to reveal the biodiversity and its spatial and temporal distribution patterns. The long-term changes in their structural characteristics were then analyzed to identify the main infl uencing factors and several measures for lake restoration were put forward. Thirty six species, belonging to 9 family and 30 genera, were collected, amongst which, the order Cypriniformes accounted for 61.1% of the total species number. In terms of importance value, Cypriniformes was the predominant group, Coilia nasus the dominant species, while Cyprinus carpio and Rhinogobius giurinus were the subdominant taxa. The community types did not differ among stations, but between seasons. There were no significant differences between seasons and among stations in species diversity, but richness differed both spatially and seasonally. Along with the process of eutrophication and the drastic reduction of the area colonized by macrophytes from 1959 to 2009–2010, the fish diversity declined markedly, and species numbers of herbivores and piscivores declined proportionately more than those of invertivores, omnivores, and planktivores. The decline of potamophilus and river-lake migratory fish was more marked than those of sedentary, river-sea migratory, and estuarine fishes. Eutrophication concomitant with sharp reduction of macrophyte area and overfishing may be the main reasons for the decline in fish diversity in Dianshan Lake.     

感潮河网水环境容量影响因素研究

研究了感潮河网的水环境容量。研究表明影响感潮河网水环境容量的主要因素为:潮汐作用、调蓄库容、水利工程的调控运行、污染物的降解系数和边界引水水质。基于感潮河网水质模型,完善了其水环境容量的计算方法。以上海市浦南东片河网为例,分析了感潮河网水环境容量在上述因素影响下的时空变化规律,并提出了相应条件下的污染物日允许排放量