Effects To Water Quality Of Feed Residues And Feces In Channal Catfish (Ictalurus Punctatus (Rafinesque)) Culture

Channel Catfish is one of the main cultured breeds in Hubei province,which is mostly adopted in cage culture.This paper studied the proportion of N and P in both feed and Channel Catfish.The contamination load of N and P in Channel Catfish cage culture were investigated. Channel Catfish’s feed residues rate was measured by indoor simulation.The amount of feces was calculated by digestion rate.The amount of N and P in excretion was counted by difference way.N and P balance in Channel Catfish cage culture was studied.The impact of feed residues and feces on water DO,pH,TN,TP,NO₃^--N,NO₂-N,NH₃-N.was investigated.The result was as follow.1.The contamination load of N and P in Channel Catfish cage cultureThe TN and TP contents of Channel Catfish’s feed were 5.18%and 1.38%and for fish were 2.53%and 0.59%.The environmental load rate of N and P in Channel Catfish cage culture were 43.77kg/t and 12.5kg/t.2.N and P balance in Channel Catfish cage cultureChannel Catfish’s feed residues rate was 14.8%,N and P in faeces accounted for 9.93%and 43.34%of N and P in feed devoted while excretive N and P accounted for38.64%and 9.79%of N and P in feed devoted respectively.The balance equation of Channel Catfish cage culture was that:100%（feed）=14.8%（feed residues）+32.07%（fish）+43.3%（faces）+9.79%（excretion）. 3.The effect of feed residues to water quality0.5 g feed was put into 1L distilled water,DO reduced from 7.11 mg/L to 0（25℃） after the feed residues enter into water.The temperature is higher,DO is falling faster,pH reduced from 6.9 to 6.0 in 18 hours,then it increased to around 6.4 and tending to steady in the 24h.The TN consistence in water are increasing from zero to 9.28mg/L,5.31mg/L and 4.11mg/L at 30℃,25℃and 20℃in eighth day.The TN is going up to 4.37mg/L,4.11mg/L and 3.86mg/L.NH₃-N consistence in water is raising apart to 6.57mg/L,3.56mg/L and 1.73mg/L.The temperature is higher,the releasing speed of TN,TP and NH₃-N is quicker,finally the consistence is higher.At 25℃NO₃^--N in water is raising zero to 0.32mg/L in a day,dropping to 0.07mg/L and being steady in the third day.NO₂^--N consistence of water at 30℃and 25℃is hoisting slowly to 0.005mg/L and 0.004mg/L,however, NO₂^--N of water at 20℃is raising from zero to 0.003mg/L in first day but dropping to 0.001mg/L in second day and stabilizing on this consistence.4.The effect of feces residues to water quality0.5 g feces was put into 1L distilled water,DO reduced from 7.11mg/L to 6mg/L and being steady at 25℃.pH reduced from 6.9 to around 6.4,after that it increased to about 6.9 and going to be steady in the 24h.The TN consistence of water are increasing from zero to 1.27mg/L,1.06mg/L and 0.88mg/L at 30℃,25℃and 20℃.The TN is going up from zero to 1.15mg/L,1.11mg/L and 1.00mg/L.NO)2^--N consistence of water is raising apart to 0.028mg/L,0.023mg/L and 0.012mg/L. NH₃-N consistence of water is raising to 0.53mg/L,0.33mg/L and 0.00mg/L.The temperature is higher,the releasing speed of TN,TP,NO₂^--N and NH₃-N is quicker,finally the consistence is higher.At 30℃NO₃^--N in water is raising zero to 0.14mg/L in one day,dropping to 0.08mg/L and being steady in fourth day.