中文摘要：

蜉蝣在河流生态系统中发挥着重要作用。2003年6月至2004年6月间对汉江流域二级河流——黑竹冲河蜉蝣优势种类的生产力及其营养基础进行了为期一周年的调查研究。结果表明，优势种小裳蜉（Leptophlebia sp．）和蜉蝣（Ephemera sp．）的生活史均为一年两代，两世代之间界限比较明显；小裳蜉的羽化主要发生在秋季和冬季，而蜉蝣的羽化主要发生在夏季和冬季。小裳蜉和蜉蝣种群的生物量和多度均出现两次峰值。采用体长频率法测算的周年生产量分别为：小裳蜉，38．0362g／m^2·a，P／B为11．4；蜉蝣，76．0318g／m^2·a，P／B为11．8。两种蜉蝣的主要食物为无形态碎屑和硅藻，其中：无形态碎屑分别占小裳蜉和蜉蝣食物组成的81．7％和94．6％，对其生产量的贡献率为59．2％和84．9％；硅藻占小裳蜉和蜉蝣食物组成的16．8％和1．5％，对其生产量的贡献率为36．4％和4．1％。

英文摘要：

Mayfly plays an important role in material cycle and energy flow in riverine ecosystem. During June 2003 to June 2004, an investigation on production and its trophic basis of dominant species of mayfly was carried out in a second-order river of the Hanjiang River Basin. There were six types of habitats to sample. Station 1 （S1） was in the middle of the stream with big round rocks in the upper reach of the stream, station 2 （S2） in the inner part of a weir with cobble substratum, station 3 （S3） in the middle of a peacefully flowing section with gravel-sand bottom, station 4 （S4） at the side of the riparian with aquatic macrophytes and snags, station 5 （S5） in the middle of the riffle and station 6 （ S6） at the lower reach with a sewage outlet ca 100 meters upper. At each station,two quantitative samples were taken with a 167μm D-frame kick net or a Surber net, and the samples were sieved with a 167μm net, sorted in a dish with naked eye,fixed in 10% formalin for later processing. The life cycle of Leptophlebia sp. and Ephemera sp. was analyzed by the monthly size frequency method, and then cohorts and annual production were estimated. The results showed that Leptophlebia sp. and Ephemera sp. both developed two generations per year. The pupation of Leptophlebia sp. mainly occurred in fall and winter;while pupation of Ephemera sp. mainly in summer and winter;the abundance and biomass of the Leptophlebia sp. reached their highest peaks （913 ind/m^2, 0.9920g/m^2） in October and August, respectively, while the abundance and biomass of the Ephemera sp reached theirs （107ind/m^2,2.3639g/m^2） in June and March. The cohort production and cohort P/B ratio of the Leptophlebia sp. population were 19.0181 g/m^2·a and 5.7, the annual production and P/ B ratio were 38.0362 g/m^2·a and 11.4. The cohort production and cohort P/B ratio of the Ephemera sp.population were 38. 0159g/m^2·a and 5.9, the annual production and P/B ratio were 76.0318g/m^2· a and 11.8. Gut content analyses showed that b