| Erythroculter ilishaeformis (Bleeker),as one of the famous "Three Treasures of Taihu Lake", is one of the major commercial fishes with high quality in the Changjiang valley.Now it is cultured in12provinces of our country, including Hubei province, Guangdong and so on, and makes good economic and social benefit. In recent years, economic benefits of Erythroculter ilishaeformis (Bleeker) have been influenced with breeding waste and environment polluted。Studies were done to compare the effects of adding bio-filter, using mixed bio-formulation and planting Ipomoea aquatica. Research focused on control and quality of pond water environment. Discussion had been taken to improve the breeding mode and attain the Requirement for Water Discharge from Freshwater Aquaculture Pond.And in that way to reduce the disease incidence of Erythroculter ilishaeformis (Bleeker) and achieve the Quality standard of no-harmful Aquatic products1.Recovery test of aquaculture water body of Erythroculter ilishaeformis using bio-filterBio-brushes and bio-balls were put in the trial ponds farmed top-mouth culters (Erythroculter ilishaeformis Bleeker) to study the effects of bio-brushes and bio-balls on growth rate, water quality and bacteria quantities in the ponds. The results indicated that the growth rate showed an increasing trend in the trail pond, but there were no significant effects on water temperature, pH, DO, TP and H2S in the trail pond compared with that in the control. However, COD in trail pond at30d, NH4+-N in trail pond at90d and NO2--N intest pond at60d and90d were all significantly lower than that in the control pond, respectively. The quantities of heterotrophic bacteria both in the water and bio-balls in the trail pond significantly increased at30d and the quantities of heterotrophic bacteria in bio-brushes significantly increased at30d and60d compared with the control pond. The quantities of ammonifier and denitrifying bacteria in water, bio-balls and bio-brushes of the test pond were all significantly increased compared with the control at90d. Furthermore, the quantities of vibrios in test pond water at30d and in bio-balls at90d significantly decreased compared with that in the control pond, respectively. So it could be concluded that putting bio-filter material in pond could increase the quantities of heterotrophic bacteria, ammonifier and denitrifying bacteria, reduce the quantities of vibrios, improve the water quality and enhance the fish growth rate.2. Preliminary experiment on pond water purification with mixed bio-formulationWater quality has been determined after using mixed bio-formulation made of photosynthetic bacteria, Bacillus licheniformis and Paenibacillus for8days. The results showed that mixed bio-formulation had no evident influence on pH, water transparency and DO of the trail pond compared to the control one (P>0.05).The concentration of CODMn in the trail ponds was significantly lower than that in the control one (P<0.05); concentration of ammonia nitrogen in the4th day and subnitrate in the4th and6th day were lower than the control one with obvious difference (P<0.05); Concentration of ammonia nitrogen in the6th and8day,and subnitrate in the8th day were lower than the control one with significant difference.The results showed that synergistic removal effect of the certain three bacterium on ammonia nitrogen and subnitrate was more significant and faster.3. Preliminary experiment on pond water purification with Ipomoea aquaticaThe test of Ipomoea aquatica planted on the floating-beds had good removal effect of nitrogen content in the water body under water temperature of28～30℃.The5-day removal rate of TAN、NO2--N、NO3--N、TN and CODMn were62.8%、95.2%、90.2%、76.1%and48.2%respectively.And its root system had great ability of adsorption and interception to suspend particulate matters and clarify the water.The relationships among the cover rate of Erythroculter ilishaeformis (Bleeker) planted on the floating-beds, removal rate of Nitrogen, dissolved oxygen (DO) are yet to be further studied. |
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