草鱼(Ctenopharyngodon idellus)集约化养殖中浮游植物对饲料氮磷比的响应

Phytoplankton response to nitrogen: phosphorus ratio in fodder for intensive grass carp(Ctenopharyngodon idellus) aquaculture

为研究养殖系统中浮游植物对饲料氮磷比(N:P比)的响应,在草鱼(Ctenopharyngodon idellus)集约化养殖池塘开展不同N:P比饲料投喂的观测试验。设置两个处理组进行对比试验,分别投喂N:P比为4.74(A处理)和8.63(B处理)的配合饲料,进行为期10周的观测。结果表明,B处理组观测到更高的浮游植物生物量,推测浮游植物可能加速了水体食物链的物质循环效率,这解释了B处理组具有更高饲料效率和更高鱼产量的原因。B处理组中绿藻成为优势种类,蓝藻相对生物量显著低于A处理组,生物多样性也较低。因此草鱼集约化养殖过程中过低N:P比的饲料不利于鱼产量提高,合理的N:P比(8.63)可以更好地促进水体中浮游植物生长,抑制可食性较低的蓝藻生物量比例,间接提高饲料效率,达到养殖增产和保护环境的双重效益。

To study responses of phytoplankton to nitrogen： phosphorus ratio（N：P ratio） in fodder, we manipulated different N：P ratios in fodder to discuss the influence on phytoplankton in intensive grass carp（Ctenopharyngodon idellus） ponds. A parallel-group trial comparing two treatments was conducted： 4.74（A treatment） and 8.63（B treatment） N：P ratio in fodder. Our results showed that more phytoplankton biomass was found in B treatment, suggesting that phytoplankton might accelerate the efficiency of material circulation in aquatic food chain. The result explained the reason why there were higher fodder utilization rate and heavier fish harvesting in the B treatment than those in the A treatment. Furthermore, Chlorophyta became dominant species; relative biomass of Cyanophyta and diversity of phytoplankton were significantly lower in the B treatment than those in the A treatment. Consequently, the study suggests that too low N：P ratio in fodder is not beneficial to improving fish harvesting for intensive grass carp aquaculture. Suitable N：P ratio in fodder can accelerate the growth of phytoplankton directly, suppress inedible Cyanophyta biomass and improve fodder efficiency indirectly, getting satisfied fish harvesting and environment protection simultaneously.