| Biofloc system as a new technology of ecological and environmental protection has been concerned by aquaculture industry.Ammonia-N can be removed quickly by adding carbon sources to stimulate the assimilation of heterotrophic bacteria.It requires a large amount of carbon source and high level of dissolved oxygen,which is more expensive and difficult to manage.Nitrifying bioflocs system transforms Ammonia-N to Nitrate-N by Nitrification reaction,which requires a few carbon source and low level of dissolved oxygen,therefore it reduces the culture cost and management difficulty.This paper explores the application of nitrifying biofloc system in Litopenaeus vannamei culture on domestication and after domestication.The main results are as follows:1)A 40 days culture for Litopenaeus vannamei in the period of domesticating the biofloc into nitrifying biofloc.Culture pond size(4.0×6.2)m,water depth 0.8 m,effective water volume 19.84 m3,total of 9 ponds.According to 400 ind /m3 stocking density to a certain size of Litopenaeus vannamei(Intial length 3.9±0.94 cm,Intial weight 0.47±0.31 g).The Total ammonia nitrogen and Nitrite nitrogen first increased and then decreased,while Nitrate nitrogen continued to rise,which accords with the construction law of nitrification system.The survival rate of Litopenaeus vannamei was(36.16 + 0.32)%,specific growth rate(3.63 + 0.00)% and production(0.30 + 0.27)kg/m3.The results showed that the high density culture of Litopenaeus vannamei in the construction of nitrification system had a great influence on the growth and survival of Litopenaeus vannamei,which was not conducive to the breeding.It was suggested that the nitrifying biological floc system should be completed and then the shrimp culture was carried out.2)The heterotrophic biofloc system was domesticated to nitrifying biofloc system,try to use nitrifying biofloc system to culture Litopenaeus vannamei,and by setting different stocking density,to explore the influence of nitrification type biofloc systems under different culture density on growth performance and quality of Litopenaeus vannamei.There are five different stocking density treatments,including 600,400,300,200 and 100 ind/m3.There are some healthy Litopenaeus vannamei in same size(body length 4.8 + 0.25 cm,body weight 0.98 + 0.16 g)were selected to culture 45 days at different stocking density treatments.The results showed that: 1)Nitrifying biofloc system can ensure the stability of water quality with 400 ind/m3 culture density,and the water quality worse over 400 ind/m3 culture density,the survival rate is reduced.2)In Nitrifying biofloc system,with the increase of culture density,the production of Litopenaeus vannamei also increases in the range of the 100~600 ind/m3,and growth rate is fastest at the 300 ind/m3.3)A 70 days culture for Litopenaeus vannamei in Nitrifying biofloc system.Culture pond size(6.0×6.6)m,water depth 0.9 m,effective water volume 32.4 m3,total of 36 ponds.According to 20 thousand P5 postlarvae per pond.The total ammonia nitrogen concentration was relatively stable during the breeding period,and there was no severe fluctuation,with a concentration level of(2.84 + 0.68)mg/L.Nitrite nitrogen concentration fluctuated greatly,but at a low level,its concentration level(0.12 + 0.08)mg/L was in the safe concentration range.Nitrate nitrogen concentration was stable at 0~60 days,and increased significantly after 60 days,with an overall concentration level of(49.51 + 5.54)mg/L.The survival rate of Litopenaeus vannamei was(41.45 + 0.16)%,specific growth rate(6.60 + 0.01)% and yield(0.36 + 0.14)kg/m3.The results showed that the nitrifying biological floc system could stabilize the water environment of high density Litopenaeus vannamei culture and ensure the growth of shrimp. |
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