Seasonal variation and longitudinal distribution of copepods in the main river area of the Three Gorges Reservoir
三峡水库初次蓄水后干流库区桡足类的纵向分布与季节变化

The ecosystem of the Three Gorges in Yangtze River was changed into an artificial lake(reservoir) ecosystem after impoundment in June 2003.We surveyed the seasonal variation and spatial distribution of copepods from April 2004 to January 2005 in order to provide basic data for clarifying the successional pat-tern of the ecosystem.From Jiangjin to Maoping,eight copepod species were collected,belonging to Ca-lanoida,Harpacticoida,and Cyclopoida.Of these,Mesocyclops pehpeiensis,M.leuckarti and Sinocalanus dorrii had a relatively wide distribution.No distinct difference in species number was found among sampling sites,but the species composition was different.Species composition,distribution and density of copepods showed significant seasonal variation.Copepod density showed an obvious gradient with the distance from the reservoir dam:the nearer to the dam,the denser the copepods.