Effect Of Integrated Culture And Addition Of Carbon Source On Water Quality, Nitrogen And Phosphrous Recovery Of Marbled Eel(Anguilla Marmorata)Farming Tanks

Integrated Multi-Trophic Aquaculture(IMTA) is an environmental and econimic aquaculture model that can enhancing water quality and provide varieties of aquaculture species. Biofloc technology(BFT) is a new idea toward water treatment,which aims to balance carbon and nitrogen in the aquaculture system, by adding carbohydrate source to the pond, heterotrophic bacteria in water can convert ammonia nitrogen into bacteria protein and fiocs which can be consumed as a source of diet by the cultivated aquatic organisms, thus the water quality and utilization of feed is improved. BFT has been applied to aquaculture, especilly in shrimp, tilapia and some other economic aquatic animals. However, performance of integrated marbled eel(Anguilla marmorata) farming is poorly understood. So an integrated culture system of marbled eel(Anguilla marmorata), tilapia and water spinach was set up. Besides,biofloc technology was also been introduced,to evaluate the effects of two kind of technology on biomass,water quality, nitrogen and phosphorus utilization and economic of marbled eel.1.To compare growth performance and nitrogen, phosphorus recovery in differen marbled eel aquaculture models, a 48-day trial was carried out in 12 indoor cement tanks(3 × 5 × 1.2). Four treatments including marbled eel, marbled eel— tilapia,marbled eel—water spinach and marbled eel—tilapia—water spinach were established. The results indicated that in treatment of marbled eel—tilapia—water spinach, the unit production and weight gain rate were significantly higher than the other groups(p<0.05), at 1.81kg/m3 and 131.73% respectively; and the average weight and specific growth rate were significantly higher than treatment of marbled eel— tilapia, marbled eel—water spinach( p < 0.05) at 148.18g/fish and 1.75%respectively; while nitrogen and phosphorus utilization were significantly higher than other treatments(p < 0.05). which were 35.03% and 17.96% respectively.Besides, the variation range of water temperature, p H value and DO were23.8~31.0℃, 7.26~8.68, 7.81~5.43mg/L, but no significantly difference among treatments(p>0.05). In conclusion, the integration of marbled eel—tilapia—water spinach system can improve farming production, and promote nitrogen and phosphorus utilization, which is an effctive and more sustainable aquaculture model.2.To assess the effect of adding different organic carbon source on growth performance, water quality and composition of bioflocs in marbled eel aquaculture ponds, a 78-days experiment was conducted in 12 indoor cement tanks(3×5×1.2).Four treatments A to D that is marbled eel, marbled eel— tilapia—water spinach,marbled eel—tilapia—water spinach(adding corn starch) marbled eel—tilapia—water water spinach(adding cassava starch) were set up, There was no water exchange during the trial. four treatments were fed two times daily limited to commercial feed of marbled eel, besides, the addditive amount of organic carbon source was 75% of feed intaked by marbled eel, and the C/N was 12. The results indicated that marbled eel biomass in Grroup C(30.51kg/pond), D(30.09 kg/pond)were significantly higher than A(26.43 kg/pond) and B(27.45 kg/pond)(p < 0.05),besides, the similar regulation were found in average weigh、specific growth rate and weight gain rate of marbled eel, in fact of feed coefficient, treatment of C(1.87),D(1.57) were lower than A(2.32)(p < 0.05),but no significantly different among treatments C and D(p>0.05),while compare Awith the other treatments,we found that treatment of Integrated Multi-Trophic Aquaculture(IMTA) was superior to culture of single species in marbled eel growth performance. On the other hand, the water quality was enhanced whule adding organic carbon source, comparing with the others treatment, at the end of trial,the concentration of TN, TP, NO2--N, NH4+-N were significantly reuced, but we also discovered that,though the concentration of NO2--N, NH4+-N were lower than no adding organic carbon source in C and D, the varied range among the trial were acute, it may be caused due to the actually feed by marbled eel was different. Durinng the experiment, the concentration of chlorophyll a does change with temperature while COD changed with mount of biofloc. Analyze element of biofloc,treatment of C(21.88%), D(23.68%) were significantly higher than A(17.33%) and B(16.89%)(p<0.05) in protein. So adding organic carbon source in system of marbled eel(Anguilla maromrata), tilapia and water spinach can inhance the biomass of aquatic organism and improve water quality.3.To evaluate the effcets of combining biofloc with IMTA model of marbled eel(Anguilla marmorata), tilapia and water spinach on economic benefit and nitrogenand phosphorus utilization, the trial was carried through the condition of chapter 3,profit rate on cost was chosen as the index.results showed that, nitrogen and phosphorus utilization in C(31.43%,14.14%)、D(28.04%,13.69%) were significantly high than A(18.43%,9.23%)、B(19.91%,8.42%)(p<0.05). So, adding organic carbon source can incease the utilization of nutrient element in feed. At the ending of experiment, profit rate on cost of C(44.38%) was higher than A(27.09%) and B(32.73%))(p<0.05).The combination of the IMTA model and biofioc technology have an activily effcet on water quality, biomass, nitrogen and phosphorus utilization and claimed higher profits economic in marbled eel farming.