To examine the effect of different two-carp ratios between silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys nobilis cocultured in the mussel pond on growth of freshwater pearl mussel Hyriopsis cumingii and water quality, an enclosure experiment was carried out in Tangxi of Zhejiang Province from April 23 to September 21,2008. Two-carp ratio was set at six levels:0/0(control group), 100/0,70/30,50/50,30/70 and 0/100. Shell length, shell width and wet weight of pearl mussels were measured at the beginning and the end of the experiment, respectively; and the water quality parameters including NO3-N, NO2-N, NH3-N, TN, TP, PO4-P, COD were determined twice a month during the experiment. The results showed that the relative growth rate of mussel shell length in level 100/0 (silver carp vs. bighead carp ratio) were significantly lower than that of levels 0/0,50/50 and 0/100(P<0.05) ,and no significant differences were found among survival rate,growth rate of shell width and wet weight of mussels at various polyculturing two-carp ratio levels (P >0. 05). Besides, enclosures at level of 30/70 had better water quality in which TP was significantly lower than 100/0(P <0.05) ,COD was significantly lower than 100/0 and 70/30 ( P < 0. 05), NH,-N was significantly lower than 100/0 (P < 0. 05) and PO4-P was significantly lower than 70/30 (P <0.05). So the ratio of 30/70 of silver carp vs. the bighead carp was the best polyculture ratio for mussel culture in terms of the growth and water quality parameters.%2008年4月23日-9月21日通过围隔实验,研究了不同鲢鳙混养比例对三角帆蚌生长及水化学指标的影响.实验中鲢鳙混养比例设置了6个水平,分别为0/0(对照组),100/0,70/30,50/50,30/70和0/100.实验开始和结束时测量三角帆蚌湿重,壳长和壳宽.每个月上下旬测量围隔水化学指标包括NO3-N、NO2-N、NH3 -N、TN、TP、PO4 -P和COD.实验结果表明,鲢鳙混养比例100/0的围隔蚌壳长相对生长率显著低于混养比例0/0,50/50和0/100的围隔(P＜0.05),而不同混养比例下蚌的成活率、蚌壳宽及蚌重增长均无显著差异(P＞0.05).从水质来看,混养比例30/70围隔TP显著低于100/0(P＜0.05),COD显著低于100/0及70/30(P＜0.05),NH3-N显著低于100/0(P＜0.05)以及PO4-P显著低于70/30(P＜0.05).因此,综合蚌生长及水质指标,混养比例30/70围隔对三角帆蚌养殖最有利.
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