对虾单养和对虾-罗非鱼混养试验围隔氮磷收支的研究

Study on nitrogen and phosphorus budgets of experimental enclosures with shrimp monoculture and shrimp-tilapia polyculture

采用18个36m2的围隔进行对虾单养和对虾罗非鱼混养试验,研究其氮磷收支的差异。各围隔放养对虾(全长为0.045 cm)均为3 000尾,放养罗非鱼((201±25)g/尾)分别为0尾(F组)、4尾(A组)、8尾(B组)、12尾(C组)、18尾(D组)、24尾(E组),试验期间各围隔均不进行水交换,试验周期为70 d。结果表明,饲料和水环境调控剂是输入氮磷的主要来源,两者在对虾单养组中占氮磷总输入的87.8%和97.9%,在对虾混养组中占氮磷总输入的81.8%～91.9%和96%～98.7%。养殖生物和底泥沉积是氮磷输出的主要渠道,对虾单养组养殖生物占氮磷总输出的23.4%和10.5%,底泥沉积占氮磷总输出为50.5%和80%;对虾混养组中养殖生物占氮磷总输出的36%～47%和14.8%～18.1%,底泥沉积占氮磷总输出的28.1%～39.4%和72.3%～78%。C组为效果最佳组,养殖生物对氮磷的利用率分别为47%和18.1%,其中对虾对氮磷的利用率分别为36.9%和16%,均大于其他混养组,且显著大于单养组(p<0.05)。研究表明,对虾与罗非鱼混养明显提高了养殖生物对氮磷的利用,减少了氮磷在池塘底部的沉积,凡纳滨对虾(8.3×105尾/hm2)和罗非鱼(3 320尾/hm2)混养可取得较好生态效益和经济效益。

The present paper is to introduce our experimental research results on the evaluation of nitrogen（short for N） and phosphorus（ short for P） budgets of shrimp monocuhure and shrimp-tilapia mixed-culture through a case study of 18 enclosures. The process of culture should be arranged in the following way： all of the enclosures were put in 3 000 young-shrimps （ Penaeus vannamei ）, in which F, A, B, C, D and E enclosure groups were allowed to be stocked with 0, 4, 8, 12, 18 and 24 tilapias, respectively. The weight of tilapia should be about （201 - 25） g/ind, with no water-exchange done in all of the enclosures during the experimental process. The whole experiment process should last 70 days. The following is the main experimental results： Of all of the input items, the major inputs of N and P are feed and fertilizer, with 87.8 % for N and 97.9 % for P in shrimp monoeulturing enclosures 91.9% for N and 96%-98.7% both of which account for 81.8%- for P in shrimp-tilapia polycuhuring enclosures. While the major outputs of N and P were biomass harvest, the uptake by muds were of all the output items. The actual biomass harvest should include 23.4% of total N input and 10.5% of total P input. And the uptake by muds may comprise 50.5 % of N input and 80% of P input in the shrimp monocuhure enclosures. In contrast with the shrimp monocuhure enclosures, in shrimp-tilapia polycuhure enclosures, the biomass harvest include 36 %- 47 % of total N input and 14.8 %- 18.1% of the total P input and the uptake by muds comprises 28.1%-39.4 % of N input and 72.3 % - 78 % of P input. Moreover, group C is the best benefit in the experiment. The biomass harvest of group C comprises 47 % of total N input and 18.1% of total P input. Besides, the ratio of N and P consumed by the shrimp in Group C turned to be higher than any other groups. The results indicate that the shrimp-tilapia mixed-culture helps to improve the ratio of N and P consumed while the ratio of N and P uptake turned to be decrease by muds. Therefore, it can be concluded that mixed-culture of shrimp at the level of 8.3 × 10^5 ind/hm^2 and tilapia at the level of 3 320 ind/hm^2 tends to demonstrate better ecological and economic advantages.