Studies On Purification Performance And Producties Efficiency Of "IPRS-shrimp-carb" Series Pond Recirculating Aquaculture System

In this research,through the construction of"IPRS-shrimp-crab"series pond recirculating aquaculture system,multiple functional areas were set up in the system to realize the recycling of aquaculture tail water in the system in the way of pure ecological purification,and the traditional"closed water purification"was changed into"circulating water".On the basis of traditional water aquaculture,new shrimp and crab breeding area as“breeding+purification”double functional areas were set up,the water quality indicators and biological indicators in each region of the system were monitored for four months to evaluate the feasibility,sustainability and comprehensive operation effect of the breeding mode and provide more models for green aquaculture.The main findings of this paper are as follows:1. Water quality index evaluation of"IPRS-shrimp-crab"series pond rcirculating aquaculture systemConstruct and operate the"IPRS-shrimp-crab"series pond recirculating aquaculture system,the aquaculture system consists of six functional areas,such as the In-pond raceway system,the sewage collection area,the constructed wetland purification area,the shrimp breeding area,the crab breeding area,and the purified water recycling area.There are four sampling points in the experimental base,and three parallel samples are taken from each sampling point.During the period from May to August in 2019,the sampling will be conducted once a month in the middle of each month for a total of 4 times.The sampling time betweem 9 am and 11 am,with a total of 4 sampling points[the front of the In-pond raceway（A）,the sewage collection area（B）,the constructed wetland（C）,and the outlet of the shrimp and crab（D）],three parallel samples were taken for each sample point,respectively,to collect the mixed water samples in the upper and middle layers.Sampling time is on May 14,June 12,July 15,August 16,sampling time for morning 9:00-11:00,determination of temperature（T）,p H,dissolved oxygen（DO）,transparency（SD）,total nitrogen（TN）,total phosphorus（TP）,ammonia nitrogen（NH₄⁺-N）,nitrite nitrogen（NO₂^--N）,chemical oxygen demand(COD_Mn),chlorophyll a（chla）and related indicators.,the eutrophication of water body in each functional area was evaluated by comprehensive state index method.The results showed that the order from the highest to the lowest was:sewage collection area>the outlet of the shrimp and crab>the front of the In-pond raceway>constructed wetland;there was a significant difference between May and July sewage collection area,SD,TN,TP,NO₂^--N,chla of the constructed wetland and and the outlet of the shrimp and crab and no significant difference between July and August,it indicates that the level of nutrient increases to some extent with the increase of temperature,and the index of nutrient tends to stabilize with the operation of the system. circulation system were respectively 8.23%,33.41%,18.44%,15.95%,20.98%and30.41%,among which most of the breeding water was in a state of slight eutrophication.Research suggests:the water quality index,removal rate and eutrophication were analyzed and evaluated.Compared with the current mature breeding system,but the removal efficiency still needs to be further enhanced,the nutrient content and eutrophication degree were within a reasonable range,but the overall operation effect was better.2. Evaluation of biological indicators of"IPRS-shrimp-crab"series pond rcirculating aquaculture systemThe sampling point and time of phytoplankton and zooplankton are the same as above.With the operation of the system,the phytoplankton density and biomass in each region gradually increased.The maximum density of phytoplankton in the breeding system was 4.33×10⁶ind/L,which appeared in the sewage collection area on July 15,and the minimum value was 1.89×10⁶ind/L,which appeared in the constructed wetland on June 12,so the range of phytoplankton density in the system was1.89×10⁶～4.33×10⁶ind/L.The maximum biomass of phytoplankton in the system was12.24 mg/L,which appeared in the sewage collection area on May 12,and the minimum value was 2.99 mg/L,which appeared in the constructed wetland on June 12,so the range of phytoplankton biomass in the system was 2.99～12.24 mg/L.The variation range of diversity index H’was 4.16 to 4.81,,the order of diversity index H’from high to bottom is:the sewage collection area>the front of the circulating aquaculture tank>the outlet of the shrimp and crab>the constructed wetland.The variation range of Pielou evenness J was 0.52～0.58,the order of Pielou evenness J from high to bottom is the constructed wetland>the outlet of the shrimp and crab>the sewage collection area>the front of the In-pond raceway.The variation range of richness index d was2.29～4.23,the order of richness index d from high to bottom is:the constructed wetland>the outlet of the shrimp and crab>the front of the In-pond raceway>the sewage collection area.The maximum zooplankton density in the breeding system was 8.46×10⁴ind/L,which appeared in the sewage collection area on July 15,and the minimum value was 4.29×10⁴ind/L,which appeared in the constructed wetland on May 14,so the range of zooplankton density in the system was 4.29×10⁴～8.46×10⁴ind/L.The maximum biomass of zooplankton in the system was 9.71 mg/L,which appeared in the sewage collection area on July 15,and the minimum was 3.81 mg/L,which appeared in the front of the flow tank on May 14,so t the range of zooplankton density in the system was 3.81～9.71 mg/L.The variation range of diversity index H was 3.86～4.78,the order of diversity index H from high to low is:the front of the In-pond raceway>the sewage collection area>the constructed wetland>the outlet of the shrimp and crab.The variation range of Pielou evenness J was 0.51～0.58,the order of Pielou evenness J from high to low was:the outlet of the shrimp and crab>the front of the In-pond raceway>the sewage collection area>the constructed wetland.The variation range of richness index d was 3.34 to 5.11,the order of richness d was from high to low was:the front of the In-pond raceway>the sewage collection area>the outlet of the shrimp and crab>the constructed wetland.Research suggests:after the aquaculture water passes through the purification zone,the density and biomass of phytoplankton and zooplanktonin the water drop rapidly,it indicates that the decrease of nutrient level limits the growth and reproduction of phytoplankton and zooplanktonin,however,shannon-weaver diversity index H,Pielou evenness index J,and richness index d of phytoplankton and zooplanktonin showed an overall rising trend with the passage of time,it indicates that the community structure of biological in the system is gradually improved and the water environment is more and more stable,which is more conducive to strengthening the self-purification ability of water quality.3. Evaluation of the yield and economic benefit of"IPRS-shrimp-crab"series pond rcirculating aquaculture systemThe total weight of Micropterus salmoides in IPRS is 15553kg,the carb is 164.5kg,the shrimp is 747.6kg,the total weight of microlepis and molitrix is 500kg,the total weight of calamus,communis and aquatica is 200kg.The total cost of the whole aquaculture system is￥456,609,the total revenue is￥569,000 and the profit is￥112,391,the comprehensive return on investment is 24.61%.In conclusion,"In-pond raceway-shrimp-crab"serial pond recirculating aquaculture system reduces the waste of water resources,improves the purification efficiency,utilization of waste and comprehensive economic benefits of aquaculture,to compared with the traditional mixed breeding mode of fish,shrimp and crab and the intensive cultivation mode of ordinary circulating water with single species,it has certain advantages,and it provides a basis for exploring a better,more green and efficient ecological breeding mode in the future.