Applications of factor-criteria system reconstruction analysis in the reproduction research on grass carp, black carp, silver carp and bighead in theYangtze River

The natural reproduction of grass carp, black carp, silver carp, and bighea d will be affected adversely by the Three Gorges Project in the Yangtze Riv er. One of the methods to save the fish is to regulate the water levels, ke eping them suited for the species to spawn. Nine factors associated with th e scale of larvae-flood of the four species are classified into five levels , and the ranges of these factors producing larvae-floods are given by usin g the "factor-criteria system reconstruction analysis" method. Moderate beg inning water levels and flow, with high daily increases in the rate of wate r level and flow, and a long duration of water level rising are important f or the production of a large larvae-flood.