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| Effects of Density and Size of Gray Mullet Mugil cephalus on Survival and Growth Performance of Pacific White Leg Shrimp Litopenaeus vannamei in Polyculture |
| PENG Yinhui,LIU Xujia,WANG Zhicheng,LIANG Zhihui,HUANG Guoqiang |
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Abstract Gray mullet Mugil cephalus juveniles were stocked into 27 tanks at a rate of 0 ,0 .13 ,0 .26 ,0 .52 , 1 .04 ,and 2 .07 ind ./m2 in large gray mullet and 0 .13 ,0 .26 ,and 0 .52 ind/m2 in small gray mullet and poly‐cultured with Pacific white leg shrimp Litopenaeus vannamei at a rate of 100 ind ./m2 to study the effects of density and size of gray mullet on survival and grow th performance of Pacific w hite leg shrimp in poly‐culture .Results showed that there was no significant difference in the yield ,size and survival of the shrimp among different groups (P>0 .05) .The yield and size of shrimp were found to be decreased with the in‐crease in density of the fish in polyculture ,lower size and yield of the shrimp in the maximal fish density groups (2 .07 fish/m2 and 0 .52 fish/m2 ) than that in other groups .There was higher survival of shrimp in polyculture groups than that in the monoculture group ,the maximal survival in the maximal fish density groups .The total yield of shrimp and fish was significantly higher in the maximal fish density groups than that in other groups ,without significant difference in total yield among other polyculture groups ( P>0 .05) .The food conversion ratio was found to be lower in polyculture groups than that in the control group ,the minimum in the highest fish density (2 .07 fish/m2 ) group ,indicating that the food utilization ef‐ficiency was increased with the increase in fish density ,without significant differences among different groups (P>0 .05) .No significant differences in water temperature ,salinity ,dissolved oxygen level ,pH ,and BOD5 were observed among different groups during the experimental period (P>0 .05) ,even though the contents of ammonia‐N ,nitrite‐N ,and nitrate‐N were higher level in middle and later experiment than early stage (P> 0 .05) ,and the content of inorganic phosphorus was maintained at constant level during the whole experimental period .The findings indicated that polyculture of gray mullet at suitable size and densi‐ty did not lead to decrease in yield of Pacific white leg shrimp ,instead of increase in survival of shrimp and food utilization efficiency ,and improvement of water quality .
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Received: 25 June 2015
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