投饵养鱼对潘家口水库水质影响围隔试验Ⅰ：氮素

摘要

在潘家口水库设置投饵（1#）、投饵单养花鲢（2#）、投饵单养鲤鱼（3#）、投饵混养花鲢和鲤鱼（4#）和空白对照5个围隔及水库背景水体，研究投饵养鱼对水体富营养化关键性因子氮素的影响。结果表明，潘家口水库是“富氮”型水体且硝态氮含量占总氮的70%左右；试验期间水库水体和对照围隔中总氮、溶解性总氮和硝态氮浓度显著高于投饵围隔，氨氮和颗粒态氮浓度则低于投饵及投饵养鱼围隔（p<0.05）；与只投饵围隔相比，养殖花鲢和鲤鱼均可显著性降低颗粒态氮和总氮浓度，但养殖花鲢或鲤鱼围隔总氮、氨氮、硝态氮浓度无显著性差异。试验结束后，捕捞围隔中花鲢、鲤鱼，经过称重和营养盐含量分析，结果发现鲤鱼增重明显大于花鲢。假定单位质量鱼肉含氮量不随鱼体生长而改变，则收获2#、3#和4#养鱼围隔中的鱼去除的氮分别占投放饵料中氮含量的3.31%、30.05%和21.18%，鲤鱼对鱼饵利用效率远高于花鲢。续文将讨论围隔试验中磷素的变化。%In order to explore the effect of fish culturing on the nitrogen flux (one of the key factors of eu-trophication) in the Panjiakou Reservoir, a set of six enclosure experiments was carried out from August 18 to October 6 in 2009. One of the water samples was directly collected in the reservoir nearby the enclo-sures, and the other five with conditions varied respectively from addition fish food only, feeding just for bighead carp (Aristichthynovilis), feeding just for carp (Cyprinuscarpio), feeding for both bighead carp and carp,and the one did nothing as control plot. The results indicate that Panjiakou reservoir is a typical“ni-trogen-rich”water, and NO3--N (nitrate) is the main constituent and accounted for 70 percents. During the experimental period, the TN (total nitrogen), DTN (dissolved total nitrogen) and NO3--N concentra-tions in the enclosures with fish food only or with both fish food and fishes were significantly lower than those in the control enclosure and reservoir water. While for NH4+-N (ammonia) and PTN (particulate total nitrogen) concentrations it was converse (p<0.05). Presence of bighead carp and carp can reduce PTN and TN concentrations significantly, while insignificant differences in TN, NH4+-N and NO3--N concentra-tions were found between presence of bighead carp and presence of carp. Assumed that the nitrogen con-tent per gram fish was constant with the fish growing, harvesting fish can remove 3.31%, 30.05% and 21.18% nitrogen respectively in enclosures with feeding bighead carp, feeding carp, and feeding both, big-head carp and carp. Hence,carp is more powerful in removing nitrogen than bighead carp.