Study On Intermediate Cultivation Density And Recirculating Aquaculture System Of The Shrimp Litopenaeus Vannamei

This study first mainly reviewed the system composition,water treatment process,typical system and existing problems of different culture systems in shrimp(fully enclosed recirculating aquaculture system,integrated multi-trophic aquaculture and biofloc culture),and the research direction of industrial recirculating aquaculture of the shrimp has been prospected.The high-throughput sequencing technology was used to detect the microbial community in the industrial rearing water body of Litopenaeus vannamei.The research about the effects of stocking density on the water quality of shrimp culture,the growth performance of shrimp and the microbial community of rearing water body was conducted.The feasibility of recirculating aquaculture system(RAS)was demonstrated by comparing the effects of indoor industrial aquaculture model and RAS on the growth performance and water quality of the shrimp in L.vannamei.And,this study also analyzed the nitrification efficiency of RAS by detecting the change of inorganic nitrogen in the cultured water before and after rearing water treatment,and tried to provide theoretical support for the application and promotion of RAS in L vannamei.The main findings are as follows:1.Effect of stocking density on intermediate cultivation of L.vannamei postlarvaeFull-scale Intermediate cultivation of shrimp postlarvae(ICSP)experiment in an aquafarm(21d)was conducted to investigate the effect of stocking density(15000-22500 pieces/m~3)on the shrimp growth performance,aquaculture water quality,and bacterial community.The results indicate that the shrimp growth performance(expressed as yield rate,special growth rate,survival rate,and feed conversion rate)was enhanced with the increasing stocking density when the stocking densities were 15000–22500 pieces/m~3.For all aquaculture ponds,the pH values and the concentrations of ammonia,nitrite and COD gradually decreased and increased,respectively over the ICSP period,while Vibrio concentrations fluctuated in the range of 0.3×10~4–7.5×10~4 CFU/mL.Furthermore,higher stocking density resulted in lower pH and higher concentrations of ammonia and COD in the water.However,little effect of stocking density on Vibrio concentration was observed in this study.At the end of ICSP,the aquaculture pond with higher stocking density had higher bacterial biodiversity.Proteobacteria(56.52–71.22%)and Bacteroidetes(20.65–38.23%)constituted the main taxonomic groups(phyla)of the bacterial community in all aquaculture ponds,and Vibrio(2.3–9.4%)was the dominant genus.2.Study on the application of shrimp recirculating aquaculture systemsFull-scale RAS experiment in an aquafarm(85d)was conducted to compare the effect of different culture systems(Indoor Industrial Flow Aquaculture,the control group,and RAS)on the shrimp growth performance,aquaculture water quality;and investigate the nitrification efficiency of RAS during rearing experiment.The results indicate that the shrimp survival rate(74.58%±1.74%),feed conversion rate(70.56%±3.82%),and production(3.91±0.49 kg/m~3)in RAS are significantly higher than the shrimp survival rate(66.90%±3.80%),feed conversion rate(67.14%±3.25%),and production(3.47±0.42 kg/m~3).Concentrations of COD(<5.92mg/L),ammonia(<0.60mg/L)and nitrite(<1.14 mg/L)are at a relatively low level within the RAS in the process of the rearing experiment.Thus,COD concentrations show an upward trend,and the highest concentration increased to 15.37mg/L,and concentrations of ammonia and nitrite fluctuate in a comparatively wide range(0.20–2.90mg/L,0.19–6.97mg/L)in the control group within the experiment.Concentrations of nitrate and total nitrogen vary in a comparatively small range(0.94–2.85 mg/L,5.95–14.01mg/L)in the control group,but concentrations of nitrate and total nitrogen show a rising trend,and the highest concentration increased to 25.98 and 33.55mg/L respectively in RAS.The effectiveness of RAS was measured by nitrification efficiency that include the removal efficiency of ammonia,nitrite(23.78–91.43%,0–27.76%)and the accumulation efficiency of nitrate(0.57–4.30%).In this study,the experiment of full-scale ICSP in the aquafarm showed that the increase of stocking density(15000–22500 pieces/m~3)could not only improve the bacterial biodiversity in the culture pond,but also improve the growth performance of L.vannamei.In this experiment,daily-increasing amount of water exchange could control the decrease of pH and the increase of COD concentration to some extent,but failed to stem the rise of ammonia and nitrite concentrations.In view of the fact that the indoor industrialized water-changing culture of L.vannamei does not effectively solve the problem of water quality deterioration caused by the increase in the amount of feeding,the intensive culture of shrimp must introduce advanced farming modes,such as RAS.In the comparative experiment of different culture models of L.vannamei,the application of RAS in the shrimp can not only control the concentration of ammonia nitrogen and nitrite,effectively increase the yield of L.vannamei,but also has high ability of the nitrogen removal,which proved that RAS is an ecologically efficient farming model.