Studies On Pond Pisciculture Modes Optimization And Exterior Nitrogen-Phosphorus Pollution Control In Zhangduhu Wetland

The Yangtze River Basin is the main fishery production base in China. In this wetland area, pond aquaculture is one of the most important fishery operations. The fish culture with chemical fertilizers dominated in most pond fishery operations and resulted in large amounts of nitrogen and phosphorus accumulated in pond sediment and lost in its receiving lakes and rivers. Silver carp Hypophthalmichthys molitrix, bighead carp Aristichthys nobilis and grass carp Ctenopharyngodon idella were the main stocking species and less economic return per hectare in this pattern of pond aquaculture compared with non traditional fishery patterns.On the basis of wetland environment conservation and wetland resources sustainable usage, the studies were conducted in the Zhangduhu wetland,Hubei province, from March 2004 to December 2005. Three fish polyculture modes with three parallels , mode A mainly stocking black carp and Wuchang bream, mode B mainly stocking grass carp, mode C mainly stocking silver carp and bighead carp were studied to compare fish stocking, growth, harvest, water quality and economic benefits.Nitrogen and phosphorus content analysis were also conducted for water inputs and outputs, fish stocked, feed inputs, fertilizers inputs, grass inputs and fish harvested to calculate the utilization and loss of these nutrients in these fishery modes. An experiment of planting lotus Nelumbo nucifera was operated from April to October in 2004. Nitrogen and phosphorus removals were calculated through inputs and outputs parameters. Economic analysis was based on costs and incomes. Physical and chemical parameters in water, total nitrogen (TN) and total phosphorus (TP) in...