Study On Structural Optimization In Composite Culture Sytem Of Ctenopharyngodon Idellus With Hypophthalimicthys Molitrix And Litopenaeus Vannamei

This study was conducted with landbased enclosures using grass carp as main cultural species. According to the complementary characteristic of different species in niche and habit, filer of sliver carp and omnivorous of Litopenaeus vanname were matched. After comparing and analyzing the benefit in ecology and economy, energy utilization of different culture systems, another more optimal composite culture mode of grass carp was built. The results could provide scientific basis for sustainable development of aquaculture in freshwater ponds of our country. Specific research results were as follows:1 Preliminary Study on Structural Optimization in Composite Culture Systems of Ctenopharyngodon idellus with Hypophthalmichthys molitrix and Litopenaeus vannameiThe preliminary study on structural optimization of composite culture systems, which included grass carp, silver carp and Litopenaeus vanname, was conducted by landbased enclosures. Since May, 2009, the variation in water quality and sediments was measured by sampling monthly. Besides, survival rate and yield of cultured species, feed conversion efficiency, utilization ratio of N and P and output-input ratio in different culture systems weren't carried out until October. The results indicated that not only harvest individual weight (>1 100 g/ind) was qualified, but also yield of grass carps(>8 400kg/ha) was satisfying, as the density of grass carps stocked was 0.77ind/m~2. Meanwhile, feed conversion efficiency(>52%) and utilization ratio of N and P in the system(N>30%, P>14%) were higher than others. When the density of silver carps stocked was 0.23ind/m~2 or 0.45ind/m~2, water quality could be improved. In addition, the mode which be stocked grass carp 0.58ind/m~2, sliver carp 0.23ind/m~2, shrimp 48.9ind/m~2, had the lowest level in the sediment pollution. Under the circumstance of this experiment, the optimal culture modes included grass carp 0.77ind/m~2, silver carp 0.45ind/m~2 in twi-species culture, and grass carp 0.77ind/m~2, silver carp 0.23ind/m~2, Litopenaeus vannamei 16.3ind/m~2 in tri-species culture. 2 Further Study on Structural Optimization in Composite Culture Systems of of Ctenopharyngodon idellus with Hypophthalmichthys molitrix and Litopenaeus vannameiThe further study on structural optimization of composite culture systems, which included grass carp, silver carp and Litopenaeus vanname, was conducted with landbased enclosures. Since May, 2010, the variation in water quality and sediments was measured by sampling monthly. Besides, survival rate and yield of cultured species, feed conversion efficiency, utilization ratio of N and P,output-input ratio and comprehensive evaluation of culture efficiency in different culture systems weren't carried out until October. The results indicated that the optimal culture mode was grass carp 0.77ind/m~2, silver carp 0.23ind/m~2, Litopenaeus vanname 20ind/m~2. This mode had the characteristics as follows: harvest individual weight and survival rate of grass carp were 1 049g/ind and 98.2% respectively, thats of silver carp and Litopenaeus vannamei were 866g/ind 100% and 10.3g/ind 50%, total gross yield was 11 500kg/hm~2, Output-input ratio was 1.33, net income was 35 446yuan/hm~2, feed conversion efficiency was 58.9%, utilization ratio of N and P in the system were 48.4% and 21.5 respectively, comprehensive evaluation of culture efficiency is 1.27. 3 Preliminary Study on Energy Budget and Conversion Efficiency in Composite Culture Systems of Ctenopharyngodon idellu, Hypophthalmichthys molitrix and Litopenaeus vannameiThe Preliminary Study on Energy Budget and Conversion Efficiency in Composite Culture Systems of Ctenopharyngodon idellu, Hypophthalmichthys molitrix and Litopenaeus vannamei, was conducted with landbased enclosures. The results indicated that the solar radiation energy input was 6658.78 MJ/m~2. In the mono-culture of grass carps, the solar energy utilization rate of phytoplankton was 0.53%, total primary productivity was 35.39MJ/m~2, total zooplankton subprime productivity was 5.41 MJ/m~2, sedimentation ratio was 55.8%, feed energy conversion efficency was 21.4%, total energy conversion efficency was 6.7%. Though sliver carps stocked reduced the solar energy utilization rate of phytoplankton(0.22～0.36%), primary productivity(14.94～24.22 MJ/m~2) and zooplankton subprime productivity(1.32～1.68 MJ/m~2). sliver carps and shrimps stocked had the function of reducing sedimentation pollution(sedimentation energy ratio 36.3～54%) and improving feed and total energy conversion efficency (25.5～27.5%, 10.2～13.4%). The optimal mode under the circumstance of this experiment was grass carp 0.77ind/m~2, silver carp 0.23ind/m~2, Litopenaeus vannamei 20ind/m~2.