配养匙吻鲟的混养塘水质变化和氮磷利用

Water Quality and N & P Utilization in Polyculture Ponds with Paddlefish Polydon spathula

研究了采用匙吻鲟(Polydon spathula)替代主养草鱼(Ctenopharyngodon idellus)的混养塘中的鳙鱼后,池塘水质变化和氮磷利用情况。结果显示:匙吻鲟混养塘的水质指标如叶绿素a、透明度低于鳙鱼对照塘,而总氨氮、亚硝酸盐氮、总氮、磷酸盐磷、总磷等一些指标的周年均值高于鳙鱼对照塘,但方差分析表明不同密度匙吻鲟混养塘之间,和对照混养塘之间的水质无明显差异,其原因可能在于匙吻鲟和鳙鱼的摄食选择差异及水体总固体悬浮物增加。试验发现,搭配放养适量低密度的匙吻鲟可提高混养塘的氮磷利用率,降低混养塘总饲料系数。初步探索出在混养塘中匙吻鲟的合理搭配密度为270尾/hm2。

An experiment was conducted without water exchange（close system） to determine the effects on the variation rules of water quality and utilization of nitrogen and phosphorus in polyculture ponds of grass carp（Ctenopharyngodon idellus） with paddlefish（Polydon spathula） instead of bighead carp（Aristichthy snobilis）.The result suggested that the mean value of chlorophyll a and transparence in paddlefish treatments was lower than the control,and the mean value of total ammonia nitrogen,nitrate nitrogen,total nitrogen,inorganic phosphorus,total phosphorus in paddlefish treatments was higher than the control.But analysis of variance（ANOVA） indicated that the water chemistry variables were not significantly different among the treatments,or between each treatment and the control.These indifferences might be caused by the different ability between paddlefish and bighead carp of switching food items,and the increasing of total suspended solids the 5 polyculture ponds.This study represented that stocking low-density paddlefish in polyculture pond might increase the utilization ratio of NP,and probably decrease the feed coefficient rate（FCR）.The hypothesis that the stocking density of paddlefish in polyculture pond was 270 ind./hm2,and had an optimistic view on stocking paddlefish in polyculture pond was supported.