Primary Study On The Main Water Quality Variation Regulation In Mandarin Fish (Siniperca Chuatsi) Rearing Ponds And Toxicity Of Ammonia To Mandarin Fish

The main water quality variation regulation in Mandarin fish pond was surveyed in the paper.The acute toxicity of ammonia and the tolerance of pH on Mandarin fish were essayed with the static test method in order to enhance water quality management.The results indicated that the main water quality factors such as pH, hardness,dissolve oxygen and chemical oxygen demand had no obvious monthly changes.The range of PH was from 7.87 to 8.27 with the mean value of 8.02,while the mean concentration of hardness was 131.43mg/L. Mandarin fish grew well in neutral and alkalescence soft water.The range of dissolve oxygen was 3.31mg/L-4.48mg/L with the mean of 3.91 mg/L,while the range of chemical oxygen demand was from 7.04 mg/L to 11.05 mg/L with the mean value of 8.82mg/L.The sum of three nitrogen(nitrate-N, nitrite-N and ammonia-N) had the lowest value of 0.061mg/L in June and the highest value of 0.695mg/L in August with the mean of 0.416mg/L.The percentage of ammonia-N,nitride-N and nitrate-N were 67.8%,9.1%and 23.6%,respectively.The mean value of phosphate was 0.021mg/L.The concentrations of three nitrogen and phosphate were higher from August to October.The ratio of nitrogen and phosphorus were 19.8 to 1.The nitrogenous accumulation may be resulted from that ammonia nitrogen was not effectively utilized due to lack of available phosphorus.The dissolve oxygen and ammonia nitrogen have obvious day and night changes.The range of dissolve oxygen was 2.37 mg/L-11.27 mg/L with the highest value in 15:00 P.M and lowest in 6:00 A.M.The water quality was evidently improved when the rearing pond was employed calcium oxide.The results also indicated that the half lethal concentration(LC50) of 24, 48,96 h and safe concentration for ammonia to Mandarin fish fingerling were 0.763,0.663,0.525 and 0.0525mg/L,respectively,pH tolerance range of Mandarin fish fingerling was from 4.10 to 9.10.Therefore,Mandarin fish cultivated pond should be supplied phosphate and calcium oxide in order to reduce the accumulation of ammonia nitrogen and accelerate transformation of substance as well as prevent the occurrence of fish disease.