鲢鲴混养对水体环境的影响

Effect of polyculture of silver carp and Xenocypris on water environment

为评估鱼类混养及其排泄物对水体环境的潜在影响,采用室内受控实验研究了鲢(Hypophthalmichthys molitrix)和黄尾鲴(Xenocypris davidi)混养对水体鱼腥藻和水质的影响。实验设置鲢投放组、鲢鲴组合投放组和空白对照组,实验周期14 d。结果发现,鱼类的放养增加了实验水体的营养负荷,有鱼实验组水体中总氮、总磷、氨氮和高锰酸盐指数均高于对照组,且实验后期鲢组的营养盐浓度均高于鲢鲴组;有鱼实验组水体中叶绿素a浓度和藻密度均降低,且鲢鲴组较鲢组降低更为明显;黄尾鲴的加入可以减少水体中鱼类排泄物的积累,鲢鲴组鱼类生物量较鲢组多,但排泄物重量却低于鲢组;鲢鲴组对鱼腥藻的消化率更高,实验结束时达到79.33%,极显著高于鲢组(P<0.01)。即在鲢控藻的基础上,混养黄尾鲴可以减少鲢摄食鱼腥藻后的排泄物重量,减少因鱼类排泄物造成的二次污染。

In order to evaluate the potential impact of fish polyculture and its excreta on the water environment,the indoor experiment in the mixed culture system of silver carp(Hypophthalmichthys molitrix)and yellow⁃tailed carp(Xe⁃nocypris davidi)was carried out based on the feeding characteristics.The experiment set up the control group,H.moli⁃trix group,H.molitrix and X.davidi group,and the experiment period was 14 days.The results showed that the stock⁃ing of fish increased the nutrient load of the experimental water body.The indexes of total nitrogen,total phosphorus,ammonia nitrogen and permanganate in the fish experimental groups were higher than those in the control group,and the nutrient concentration in the H.molitrix group was higher than that in the H.molitrix and X.davidi group at the later stage of experiment.The concentration of chlorophyll⁃a and the density of algae in the water body of the fish experimental groups decreased,and the reduction of H.molitrix and X.davidi group was more obvious than H.molitrix group.The addition of X.davidi could reduce the accumulation of fish excrement in the water.The fish biomass of H.molitrix and X.davidi group was more than that of H.molitrix group,but the weight of excrement was lower than that of H.moli⁃trix group.The digestibility of Anabaena sp.in H.molitrix and X.davidi group reached 79.33%at the end of the experiment,which was significantly higher than that in H.molitrix group(P<0.01).As a consequence,on the basis of al⁃gae control by H.molitrix,the mixed culture of X.davidi could reduce the weight of the excrement of H.molitrix after eating Anabaena sp.,and reduce the secondary pollution of water ecosystem caused by fish excrement.