Prawn-fish-shellfish-algae optimal ecoculture and its bio-manipulation technique of water quality.

An ecological optimal aquaculture mode was established which included four aquaculture areas with different functions to culture prawn,fish,shellfish and macroalgae respectively,one water treatment area and one emergent off-taking area.Bio-manipulation of water quality can be achieved by stocking complementary organisms in different ponds within the closed circulation system.The results indicated that COD,the contents of suspension,ammoniated nitrogen and nitrated nitrogen were much lower than those of monoculture ponds (P0.01).The final drainage of the reused water was not eutrophicated (E1).The commercial benefit was obvious.Totally 0.667kg prawns,0.037kg tilapia,0.738kg oyster,and 0.437kg Gracilaria tenuistipitata were harvested with the input of 1 kg feed,with a net profit increase of $2.01 yuan.The ratio of input to output was significantly reduced from 0.709 of monoculture to 0.235 of ecoculture of prawns.Not only the bio-manipulation of aquaculture environment and null discharge of culture water were implemented,but feed conversion ratio and economic benefits were increased notably with advantages of illness-resisting,environment-protection and high-efficiency.