| The aim of this study was to investigate the production effect and ecological effect of applying fine bubble aeration systems to cage culture in large waters,and to provide references for the study of ecotype cage culture model in large waters.The study 1 used two kinds of netcages.The usual netcage as control group,the usual netcage with the addition of fine bubble aeration systems as experimental group.The growing performance,econnomic benifit and water quality indicators were measured.The following results were obtained:1.Contrast of the growingparameters and econnomic efficiency of cages(1)The daily growth ratio,special growth ratio,average weight gain of channel catfish from experimental group was obviously higher than that of control group(P<0.05).The feed conversion ration of control group and experimental group was 1.58 and 1.35,respectively.The control group had a lower SI than experimental group.(2)Theexperimental group had higher income than control group.The feed cost of two cages accounted for the largest in the total cost,respectively 78.49% and 79.58%.The proportion of finger cost of two cages was in the second place,,respectively 19.14% and 18.04%.The cost of aeration(including electricity cost and equipment depreciation)represented only 0.3% of the total cost.2.Analysis of water quality index of cages and control site(1)The blank site had significantly higher dissolved oxygen content than the cages(P<0.05).The dissolved oxygen content of the experimental group was significantly higher than that of the control group(P<0.05).The fluctuations of dissolved oxygen content is not large in two cages during the test.The pH value were between 7 to 9 during the test.There were no significant differences of the pH value among two cages(P>0.05).The transparency of the control site is higher than the transparency of two cages,but the difference is not significant.(2)The content of amonium nitrigen of the blank site was obviously less than that of the cages(P<0.01).Content of nitrat nitrogen and nitrit nitrigen in the blank site were less than that in the cages,yet the difference was not significant(P>0.05).The content of ammonium nitrogen and nitrite nitrogen in experimental group were significantly lower than that in control group.The content of nitrate nitrogen in cage B were lower than that of control group,but the difference wasn’t statistically significant(P>0.05).The results showed that the local water quality could be improved obviously after the fine bubble aeration systems were applied to the cages in the reservoirs,and the growth performance of the channel catfish was better than that of the ordinary cages.The increase in the cost of aeration is small,but the economic efficiency was significantly enhanced.This indicated that the fine bubble aeration systems was feasible for high density cage culture of channel catfish.The study 2 used two kinds of cages.Control group is normal netcages,experimental group is normalnet cages with the addition of the manure collection system.Cyprinuscarpiovar.specularis with body weight of(167.81±34.66)g was reared in those net cages for 90 days.The results showed that the growth performance of netcages with the manure collection system was significantly better than that of the normalnetcages(P <0.05).The recuperation rates of N were 76.83% in the cages with the manure collection system and 44.14% in the normal cages respectively,and the recuperation rates of P were 63.13% and 35.18%,respectively.There was significant difference between the two groups(P <0.01).The utilization rates of N were 28.36% in the cages with the manure collection system and 25.57% in the normal cages respectively,and the utilization rates of P were 21.30% and 18.25%,respectively.The utilization rates of N and P were significantly higher than those of normal cages(P <0.05).The addition of the manure collection system in the cages facilitates the growth of the box scales,while reducing the emission of nitrogen and phosphorus to the water body. |
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