Effects Of Four Probiotics On Water Quality And Growth Of Hybrid Snakehead(Channa Maculata?� C.argus?)

In recent years,hybrid snakehead has become the most important aquatic species in snakehead fish aquaculture industry.Though its scale and breeding density have been continuously growing,high-density and intensive cultivation have led to problems such as serious deterioration of hybrid snakehead aquaculture environment and frequent occurrence of diseases,significantly hindering the further development of the hybrid snakehead aquaculture industry.Using probiotics to control water quality is a highly effective and environmentally friendly means.Yet in most cases,single probiotic probiotics are used,though such agents have some limitations such as unitary treatment effect and non-ideal treatment effects.In contrast,mixed use of different probiotics as probiotics in water quality control can avoid the limitations of single probiotic products and achieve complementarity of various probiotics,thus improving culture effects.But in reality,most studies on the effects of mixed use of different probiotics in water quality control still remain at laboratory research stage,and studies conducted in outdoor aquaculture ponds are relatively small in number.Probiotics with bacillus,lactobacillus,photosynthetic bacteria and nitrifying bacteria as main components had been adoptedto control the water quality in hybrid snakehead aquaculture ponds in this study.The experiment was carried out in four outdoor ponds of the same size.Since the present experiment was an outdoor experiment,in order to reduce the influences of such factors as weather changes on the experiment,the design test period of this research was 90 days.The trends of water quality changes and fish growth indicators in a relatively long culture cycle that conforms to production practice were evaluated to prove the influences of the probiotics used in this experiment on water quality and fish growth in hybrid snakehead aquaculture.In this experiment,the water quality of ammonia,nitrite,total nitrogen,total phosphorus,phosphate,transparency and pH of water were analyzed.By analyzing the overall rules and changes of the abovementioned indicators,the influences of probiotics on water quality control were evaluated.Furthermore,the influences of microbial ecological gents on the growth of hybrid snakehead were evaluated through a test of fish growth indicators;and the influences of probiotics on phytoplanktonwere evaluated through qualitative and quantitative analyses of the phytoplankton in the ponds.Main results of the experiment were as follows: 1.Effects of probiotics on hybrid snakehead aquaculture water controlProbiotics can effectively control the concentrations of ammonia nitrogen and nitrite in waters.In the ponds of the experimental groups,concentration increases of ammonia,nitrogen and nitrite are significantly below those of the control groups;at the end of the experiment,concentrations of ammonia nitrogen of Control Group 1 and Control Group 2 are respectively 199% & 308% and 88% & 156% higher than those of Experimental Group 1 and Experimental Group 2.And concentration of nitrite of of Control Group 1 and Control Group 2 are respectively 48%& 84% and 26% & 86% higher than those of Experimental Group 1 and Experimental Group 2The probiotics used in this experiment have regulatory effects on total nitrogen and phosphate,but the effects are not stable;the regulatory effects on total phosphorus are not obvious;CODs of the experimental groups increased more slowly than those of the control groups.At the end of the experiment,COD of Experimental Group 1 are 22.9% and 29.5% lower than those of the control groups.2.Influences of probiotics on the growth indicators of hybrid snakeheadFinal weight of experimental groups aresignificantly higher than those of the control groups,with differences of respectively 14% & 8.3%and11.9% & 5.3%;Hybrid snakeheads of the experimental groups are significantly fatter than those of the control groups,with differences of respectively 15.9% & 17% and 8% & 9%;The weight increases of Experimental Group 1 are significantly more than those of control groups,with differences of 227% and 129.3%.TheSpecific growth rate of experimental groups aresignificantly higher than those of the control groups,with differences of respectively43.8% & 31.4%and25.5% & 13.1%.On the whole,the growth conditions of hybrid snakehead in the groups that use probiotics are better.3.Influences of probiotics on the growth of phytoplankton in hybrid snakehead aquaculture waters.After the experiment started,chlorophylla of the experimental groups increased rapidly,and the algal density was even higher.In the experimental groups,phytoplankton communities with such green alga as crucigenia,scenedesmus and chlorella as dominant algae were formed,whereas blue-green algae represented by microcystis took a higher percentage in the phytoplankton of the control groups.