The Studies On Ammonia Excretions By Grass Carp(Ctenopharyngodon Idellus) And Mandarin Fish(Siniperca Chuatsi) And The Effect Of Probiotics On The Water Quality Of Mandarin Fish Pond

Ammonia is considered as the end product of amino acid catabolism in fish, and it is important to know the ammonia excretion (AE) of the fish being cultured. The effects of water temperature (19±0.5℃,24±0.5℃and29零0.5℃) on AE rate were studied in grass carp (Ctenopharyngodon idellus) and mandarin fish (Siniperca chuatsi) in recirculation systems. Both fish were fed once a day with a total of1.5%body weight (BW) at8:30am and AE rate was measured during the following24h. The AE rate was increased significantly (P<0.05) with temperature from19℃to29℃, and the linear analysis showed a straight line relationship between AE rate and temperatures in feed-deprived fish (grass carp:y=0.2228x-2.2969, R2=0.9918; mandarin fish:y=0.3002x-3.8167, R2=0.9748). The maximum AE rate of grass carp and mandarin fish were observed at2-4h and4-8h after feeding, respectively, and the minimum values of both fish were observed at24h. In addition, the ammonia nitrogen excretion rates (NE)/nitrogen intake (NI) of grass carp was higher than that of mandarin fish after feeding for all temperatures as a whole. That suggested the grass carp had a higher (NE)/(NI) than that of mandarin fish at same temperature in same period. Thus, we considered grass carp made a greater contribution to environment pressure compared with mandarin fish of the same size.As the scale and density of aquaculture has increased in recent year, the water pollution in aquaculture was serious, and the industrial and agricultural sewage discharge maked it more serious. The water purification and restoration has been attention and biological repair especially probiotics has been gradually promoted. But most researches were still in laboratory level, and it is very different from the outdoor pond. So this experiment was conducted to study the application of Bacillus to water quality and plankton composition in mandarin fish (Siniperca chuatsi) and bait fish ponds, and study the application of the effect of nitrifying bacteria on water quality in mandarin fish (Siniperca chuatsi) and bait fish ponds. Water quality indexes were analyzed, such as amounts of NH4+-N, NO2--N, NO3-N, T-N, transparency and pH value; and plankton composition was analyzed in the pond. The results showed that the Bacillus could improve transparency of the experimental ponds. The contents of NH4+-N and NO2--N in the experimental ponds were reduced, and the NO2--N content reduced maximally by77.5%after18days. In addition, the variation tendency of plankton composition in experimental pond was same as that in control pond after applying bacteria. That might show the Bacillus had no effect on the plankton composition. And the nitrifying bacteria could improve transparency of the experimental pond, reduce the content of NH4+-N、NO2--N and increase the content of NO3--N at0-8d after applying bacteria. At6d after applying bacteria, the content of NO3--N in experimental pond was75%higher than that in the control pond, and31.6%higher than that before applying bacteria. Maybe due to the nitrification of nitrifying bacteria weakened, the variation tendency of water quality indicators in experimental pond were same as that in control pond at8-12d after applying bacteria. In addition, the influence of nitrifying bacteria on T-N and pH value was not remarkable.