放养密度对凡纳滨对虾苗种中间培育效果的影响

Effect of Stocking Density on Intermediate Cultivation of Litopenaeus vannamei Postlarvae

通过对养殖场凡纳滨对虾(Litopenaeus vannamei)实际苗种中间培育进行实验(21 d),探究了放养密度(1.50～2.25万尾/m^3)对凡纳滨对虾的生长性能、养殖水体水质以及细菌群落的影响。结果显示,当放养密度为1.50～2.25万尾/m^3时,放养密度的增加会提高凡纳滨对虾的产率、特定生长率、存活率及饵料转化率。实验期间,各养殖池内水体的pH逐渐下降,氨氮(NH_4^+-N)和化学需氧量(COD)浓度均呈逐渐上升趋势,弧菌(Vibrio)浓度则在一定范围内[(0.3～7.5)×10~4 CFU/ml]波动。放养密度的增加会导致养殖水体pH下降,NH4+-N和COD浓度升高,但对水体中的弧菌浓度没有明显影响。实验末期,放养密度较高的养殖池具有较高的细菌生物多样性,变形菌门(Proteobacteria)(56.52%～71.22%)和拟杆菌门(Bacteroidetes)(20.65%～38.23%)为各养殖池内主要细菌门类,而且弧菌属(Vibrio)(2.3%～9.4%)在各养殖池内均为优势菌属。在凡纳滨对虾苗种中间培育过程中,逐日增加换水量对水体pH和COD浓度具有一定的调节能力,但难以控制NH4+-N和亚硝酸氮(NO_2^--N)浓度的升高。

Intermediate cultivation of shrimp postlarvae(ICSP) is an important part of industrial shrimp farming. Full-scale ICSP experiment in an aquafarm(21 d) was conducted to investigate the effect of stocking density(15000~22500 pieces/m^3) on the shrimp growth performance, aquaculture water quality, and bacterial community. The results indicated that the shrimp growth performance(Expressed as yield rate, special growth rate, survival rate, and feed conversion rate) was enhanced with the increasing stocking density when the stocking densities were 15000~22500 pieces/m^3. For all aquaculture ponds, the pH values and the concentrations of ammonia, nitrite and COD gradually decreased and increased,respectively over the ICSP period, while Vibrio concentrations fluctuated in the range of(0.3~7.5)× 10~4 CFU/ml. Furthermore, higher stocking density resulted in lower pH and higher concentrations of ammonia and COD in the water. However, little effect of stocking density on Vibrio concentration was observed in this study. At the end of ICSP, the aquaculture pond with higher stocking density had higher bacterial biodiversity. Proteobacteria(56.52%~71.22%) and Bacteroidetes(20.65%~38.23%) constituted the main taxonomic groups(Phyla) of the bacterial community in all aquaculture ponds, and Vibrio(2.3%~9.4%) was the dominant genus. During the ICSP period, daily-increasing amounts of water exchange could control the decrease in pH and the increase in COD concentration to some extent, but failed to stem the rise of ammonia and nitrite concentrations.