Studies On The Optimization And Nitrogen And Phosphorus Budgets Of Polyculture System Of Portunus Trituberculatus Ponds

Portunus trituberculatus is considered to be one of largest marine crabsaquaculture species in China，which belongs to Crustacea, Decapoda, Portunidae.Asto lots of characteristics such as strong adaptability, rapid growth，delicious meat andhigh economic value, Portunus trituberculatus cultivation is very popular in China.But there are some disadvantages in traditional cultivation like improper managementlevels, skills shortage, low feed utilization rate，low profits and so on. These problemshave become bottleneck for the development of Portunus trituberculatus cultivation.In this study, we used land-based enclosures to study ecological and socialbenefits and conversion efficiency of different ecosystems, in which Portunustrituberculatus、Litopenaeus vannamei and Ruditapes philippinarum were cultured indifferent mono-and poly-culture treatments. The main results were as follow:1. An Experimental Study on Structure Optimization for Polyculture of Portunustrituberculatus with Litopenaeus vannameiThe study were studied with land-based enclosures with different poly-culturesystems of Portunus trituberculatus with Litopenaeus vannamei. The experiment werestudied by means of six treatments，crabs and shrimps were mixed with differentdensity into four groups, compared with the group only stocked crabs or shrimps. Theresult showed that the carapace width of crab ranged from7.26to14.29cm and thecarapace length of crab ranged from4.18to11.42cm at harvest. The highest survivalrate of crab were41.33%for the treatment of C3S2,and followed by C4S1, C2S3, C, C1S4.The highest net output of crab were2713kg/hm~2. The body length of shrimpranged from6.78to11.23cm and all the polyculture treatments were superior toshrimp mono-culture in body length. The highest survival rate of shrimp were for thetreatment of C4S1,and followed by C3S2, C1S4, C2S3, S.The highest net output ofshrimp were2699kg/hm~2for treatment of C2S3.The treatment giving the best culturingbenefit was crabs at6ind/m~2and shrimps at45ind/m~2.2. An Experimental Study on Nitrogen and Phosphorus budgets in Polyculture ofPortunus trituberculatus with Litopenaeus vannameiThe budgets of nitrogen (N) and phosphorus (P) were studied with land-basedenclosures with different polyculture systems of Portunus trituberculatus withLitopenaeus vannamei. The results showed that the feed was the main nitrogen(accounting for79.77%~91.53%) and phosphorus (accounting for94.31%~98.43%)input in the enclosures while the marine water supply provided7.06%~16.22%ofnitrogen inputs and1.12%~4.53%of total phosphorus inputs. Among the output items,the major outputs of nitrogen and phosphorus were in the sediments, which accounted for40.29%~65.89%of total nitrogen outputs and76.11%~86.54%of total phosphorusoutputs. The biomass harvest compromised8.7%~24.44%of total nitrogen inputs and14.11%~18.90%of total phosphorus inputs. The utilization efficiency of nitrogen ofpolyculture systems is higher than C system. The treatment giving the best culturingbenefit was crabs at6ind/m~2and shrimps at45ind/m~2.3. An Experimental Study on Structure Optimization for Polyculture of Portunustrituberculatus、Litopenaeus vannamei and Ruditapes philippinarumThe study was designed and conducted to optimize the structure of polyculturefor Portunus trituberculatus、Litopenaeus vannamei and Ruditapes philippinarum，and to compare their ecological efficiencies and water quality parameters. Theexperiments were studied by means of eight treatments，and conducted with land-basedenclosures setting in an earthen pond. Crabs and shrimps were mixed with clams of four different densities. The result showed that the carapace length、carapace widthand body weight of crabs in different treatments were not significantly different. Thehighest yield of crab were4269.05kg/hm~2for the treatment of CSB4，followed by3024.82kg/hm~2for the treatment of CSB3，and both of them were better than othertreatments in survival rate significantly. It showed that breeding clams in the pondwith crabs and shrimps could increase the yield and survival rate of them significantly.The highest survival rate of shrimp were70.67%for the treatment of CSB3，followedby41.74%for the treatment of CSB4，and both of them were better than othertreatments in survival rate significantly. The body weight of shrimp for the treatmentof CSB3was better than the treatment of CSB4significantly，and similar to thetreatment of CSB1and CSB2.The final size and survival rate of shrimp had negativecorrelation with the stocking density of clam. Both of the comprehensive benefit and theyield for the treatments CSB3and CSB4were better than the best treatment onlycultured crabs and shrimps last year. The treatment giving the best culturing benefit wascrabs at6ind/m~2、shrimps at45ind/m~2and clams at30~60ind/m~2.4. An Experimental Study on Nitrogen and Phosphorus budgets in Polyculture ofPortunus trituberculatus、Litopenaeus vannamei and Ruditapes philippinarumThe budgets of nitrogen (N) and phosphorus (P) were studied with land-basedenclosures with different polyculture systems of Portunus trituberculatus、 Litopenaeusvannamei and Ruditapes philippinarum. The results showed that the feed was the mainnitrogen (accounting for73.81%~89.75%) and phosphorus (accounting for96.64%~98.13%) input in the enclosures while the marine water supply provided7.14%~19.00%of nitrogen inputs and0.39%~1.11%of total phosphorus inputs. Amongthe output items, the major outputs of nitrogen and phosphorus were in the sediments,which accounted for39.88%~60.36%of total nitrogen outputs and35.69%~78.52%oftotal phosphorus outputs. The biomass harvest compromised10.14%~32.24%of totalnitrogen outputs and10.10%~33.55%of total phosphorus outputs. The highest utilizationefficiency of nitrogen and phosphorus of polyculture systems is CSB3system, followed by CSB4system. The treatment giving the best culturing benefit was crabs at6ind/m~2、shrimps at45ind/m~2and clams at30~60ind/m~2.