Study On The Functional Effect Of Biological Flocs In The Zero Water Exchange Culture System Of Micropterus Salmoides And Hybrid Snakehead

Both Micropterus Salmoides and Hybrid Snakehead are important freshwater species in China.It is of great significance to develop zero exchange aquaculture system for M.Salmoides and H.Snakehead.In this paper,biological flocs were applied to the zero exchange aquaculture system of M.Salmoides and H.Snakehead,and the influence of this aquaculture model on M.Salmoides and H.Snakehead was explored from many aspects,in order to provide theoretical basis for the healthy and efficient green aquaculture of M.Salmoides and H.Snakehead.In this experiment,biological flocs were inoculated and cultured first,and then compared with non biological flocs,three parallel groups were set up respectively.In addition to biological flocs,biological flocs were supplemented with carbon source and nitrogen source every day,and sodium bicarbonate was added to maintain p H according to the change of p H.during the experiment,the concentration of nitrite nitrogen in the experimental group and the control group increased as a whole Trend:the highest concentration value is 0.45 mg/L;the change of nitrate nitrogen concentration in the experimental group and the control group is in a fluctuating state and the concentration value is below 4.0 mg/L;from August 25 to September 4,the concentration of ammonia nitrogen in the experimental group is 1.56+0.67 mg/L,and that in the control group is3.63+1.13 mg/L;during the whole experiment,the p H value of the experimental group was always below 7.8,while that of the control group was below 8.2;the change of the total alkalinity content of the experimental group and the control group was in a state of fluctuation and the value remained within 70.0 mg Ca CO₃/L;the water temperature was basically maintained at 27+2℃during the experiment.The bioflocculus was measured in the experimental group on August 28,and the sediment was also measured in the control group one day later.Secondly,the cultured biological flocs were applied to the zero water exchange culture of M.Salmoides.Three parallel groups were set up,with a culture density of 100/m³ and 150 seedlings per group.Under this culture mode,the survival rate of M.Salmoides is 100%,the average daily growth is 0.097+0.002 cm,and the average daily gain is0.928+0.044 g.When the biological flocculent system is stable,the ammonia nitrogen concentration is maintained at about 1.0 mg/L,the nitrite nitrogen is maintained at about0.5 mg/L,the nitrate nitrogen is maintained at about 33.0+2.0 mg/L,and the p H is maintained at about 7.9+0.5 by adding sodium bicarbonate artificially.In terms of nutrition,the total amino acids of M.Salmoides in zero exchange culture of biological flocs and M.Salmoides in high level pond were（20.710+0.768）%and（20.200+1.723）%,respectively,and the contents of fresh amino acids and essential amino acids of human body were higher than those of M.Salmoides in high level pond.The floccules increased the abundance of Firmicutes,Verrucomicrobia,Bacteroidetes,Cetobacterium and Acinetobacter.In the same way,the biological flocs were applied to the zero water exchange culture system of H.Snakehead,and three parallel groups were set up,with a culture density of 50/m³ and 100 seedlings per group.The results showed that the concentration of ammonia nitrogen,nitrite nitrogen,nitrate nitrogen and bicarbonate could be maintained at 1.0 mg/L,0.5 mg/L,33.0+2.0 mg/L and 8.0 respectively.The survival rate of the three H.snakeheads was over 90.0%,with an average daily growth of 0.090+0.008 cm and an average daily gain of 1.130+0.024 g.In terms of water content and crude fat content,the content of H.Snakehead in zero water exchange culture of biological flocs was lower than that in high level pond and soil pool,especially the content of crude fat.The content of crude fat in high level pond H.Snakehead（1.580+0.323）%and soil pool H.Snakehead（1.960+0.587）%was about 2-3 times of that in zero water exchange culture of biological flocs（0.770+0.081）%.The total amino acids of H.Snakehead in zero exchange culture with biological flocs were（18.920+1.138）%、（21.193+0.358）%and（18.657+0.620）%,respectively.The fresh amino acids and essential amino acids of H.Snakehead in biological flocs culture were lower than those in high level pond culture.The biological flocs increased the abundance of Proteobacteria,Acinetobacter and Aeromonas.