The Effects of Stocking Silver Carp and Bighead Carp on Water Quality in-situ Enclosure Experiment

The in-situ enclosure experiment of stocking silver carp (Hypophtyalmichthys molitrix) and bighead carp (Aristichthys mobilis) were studied in Yunlonghu Reservoir. Twelve in-situ enclosures for five experimental treatments stocked with bighead carp only, silver carp to bighead carp ratio 1:3, 1:1, 3:1 and silver carp only, respectively, and one control without fish were built. Trophic index such as water transparency (SD), concentration of N, P, and chlorophyll were measured to evaluate the effects of stocking and different ratios of silver carp and bighead carp on the water quality. Based on research results, stocking silver carp and bighead carp in Yunlonghu Reservoir could improve the water quality. The appropriate biomass of silver carp and bighead carp was 20g/m(3) and the ratio was 1:3 for the benefit of shortening the period of culturing and raising the income and improving the water quality as well.