罗氏沼虾不同养殖模式对水体浮游生物的影响

通过围隔实验比较罗氏沼虾不同养殖模式对水体浮游生物的影响。实验设置6种养殖模式:罗氏沼虾单养(MP)、罗氏沼虾+浮萍(水面覆盖率5%)(PP)、罗氏沼虾+鲢(PF)、罗氏沼虾+背角无齿蚌+鲢(PMF)、罗氏沼虾+背角无齿蚌+浮萍(PMP)、罗氏沼虾+背角无齿蚌+浮萍+鲢(PMPF)。养殖64 d后,测定不同模式中浮游植物和三大类浮游动物(轮虫、枝角类及桡足类)的种类和数量。结果显示,上述6种模式中浮游植物共同优势种有4种,但优势度指数最大的浮游植物不同,MP组是锥囊藻属,有浮萍的PP和PMP组均为细小平裂藻,混养鲢的PF、PMF和PMPF组均为针杆藻。不同养殖模式无共同的浮游动物优势种。养殖模式对浮游生物密度具有显著影响,PF组浮游植物密度最高,MP组浮游植物密度最低,PF组浮游植物密度比MP、PP和PMP组分别高78%、53%和61%。相反,浮游动物密度MP组最高,PF组最低。混养鲢的PF、PMF和PMPF组浮游动物密度显著低于其他3组。研究表明,罗氏沼虾养殖中混养鲢可增加浮游植物密度而降低浮游动物密度,浮萍和鲢影响池塘优势种。

Effects of different cultural patterns of Macrobrachium rosenbergii on plankton

The plankton in water under six cultural patterns of Macrobrachium rosenbergii was evaluated in an enclosure experiment. The cultural patterns included prawn monoculture group (MP), prawn with aquatic plant (Lemna minor, water-coverage 5%) group (PP), prawn with silver carp (Hypophthalmichthys molitrix) group (PF), prawn with mussel (Anodonta woodiana) and H. molitrix group (PMF), prawn with mussel and aquatic plant group (PMP), prawn with A. woodiana, L. minor and H. molitrix group (PMPF). Four replicates of each treatment were set up in this study. After 64 days of culturing, the phytoplankton and zooplankton (Rotifera, Cladocera and Copepods) in water of each cultural pattern were evaluated. The results showed that there were four common phytoplankton dominant species in all cultural patterns. However, the most dominant phytoplankton species was different. The most phytoplankton dominant species were Dinobryon in MP group, and Oscillatoria minima in culturing L. minor groups (PP and PMP), and Synedra sp. in H. molitrix polyculture groups (PF, PMF and PMPF). There were no common dominant species of zooplankton in six cultural patterns. The density of phytoplankton in the PF group was the highest, and it was higher than that of MP, PP and PMP by 78%, 53% and 61%, respectively. In contrast, the density of zooplankton was the highest in MP, and that of PF group was the lowest. The density of zooplankton in H. molitrix polyculture groups (PF, PMF and PMPF) was significantly lower than that of other three groups. The results showed that the stocking H. molitrix in M. rosenbergii pond can increase the density of phytoplankton and reduce the density of zooplankton. Both L. minor and H. molitrix could affect dominant species in pond.