Feasibility Evaluation Of Shrimp Farming In Outdoor Rotifer Culture Pond

Litopenaeus vannabin is the main shrimp aquaculture species in China,but the development of vannabin shrimp aquaculture industry is limited by factors such as insufficient water supply.In order to expand the scale of P.vannabin shrimp,this study explored the use of outdoor rotifer cultivation ponds as the aquaculture water body to aerate the cultivation of P.vannabin,investigated the water quality changes,the structure composition of algae community in ponds and the evaluation of the economic benefits of the culture in the process of P.vannabin,and explored the feasibility of cultivating Penus vannabin in outdoor rotifer cultivation ponds.The specific research content and results are as follows:（1）Changes in chemical indexes of the aquatic environment of litopenaeus vannamei culture affected its growth,development,health status and yield.In this experiment,the aeration pond and non-aeration pond of outdoor rotifer breeding pond were selected as the detection objects,and the change trend of transparency,temperature,salinity,DO,p H value,COD,suspended particulate matter,organic matter,NH₄⁺-N,NO₂^--N,NO₃^--N,TP,PO₄^3--P,TP and chla were determined,and the above physicochemical factors measured in the aeration experimental pond were analyzed by SPSS.Studies have shown that the transparency of ponds gradually decreases with the increase of rearing time.The salinity of each pond in the middle and late stage of culture tended to be stable,with an average of 10.69‰,and the DO concentration of aeration pond remained at 6.5 mg·L^-1,which was on average 0.5 mg·L^-1 higher than the concentration of DO in non-aerated ponds。The variation range of COD in aeration pond water was 10.2～22.2 mg·L^-1 Between,the overall trend shows a trend of first rising and then falling.The p H value of the aeration pond ranged from 7.77～9.42,and the average value was 8.69.The mean concentrations of suspended particulate matter in aeration ponds and non-aerated ponds were 54.9 mg·L^-1 and 59.8 mg·L^-1,the average organic content was 31.3 mg·L^-1 and 28.2 mg·L^-1。Except for the No.4 pond,NH₄⁺-N,NO₂^--N,NO₃^--N and TN generally showed a trend of first decreasing and then rising,and the overall change of PO₄^3--P and TP concentration showed a slow fluctuation and rise.The content of Chla gradually increased with the length of rearing time,and the average Chla content of the three tests was 535.44μg·L^-1,691.93μg·L^-1,713.36μg·L^-1.Monitoring showed that the physical and chemical properties of the oxygenated water body in the outdoor rotifer breeding pond were within a reasonable range,which was suitable for the cultivation of litopenaeus vannamei.（2）In this study,algal communities in 21 aeration ponds were identified.A total of 6 phylums and 20 genera of planktonic algae were identified.Studies have shown that golden algae are the absolute dominant algae species with high density,and they begin to multiply in large numbers from early July as the temperature gradually rises,and continue until August.It becomes the dominant species in mid-July and continues to multiply in large numbers later onwards.The number of rhomboid algae gradually decreases after entering July,and it is no longer the dominant species by the end of July.The number of protodinoflagellates,euglenas and polydinoflagellate in the phylum dinoflagellate is large,lasting about one month,and gradually decreasing in August,after which the small cyclic algae and the group algae began to multiply in large numbers.The number of species of the diatom phylum dominates.（3）Through the evaluation of the economic benefits of the aeration shrimp culture model in outdoor rotifer breeding ponds,it is shown that this culture model has certain commercial feasibility.The survival rate of vannamei is 15%.Of the total cost of aeration ponds,the main expenses incurred are workers’wages,purchase of shrimp fry and utilities,which account for 88%of the total.The total income is 1396.05 yuan per acre,the net profit per acre is 333.06 yuan,the cost profit margin is 31%,and the sales profit margin is 24%,indicating that the outdoor rotifer breeding pond has achieved certain economic benefits.