构建硝化型生物絮凝系统过程中凡纳滨对虾养殖密度对水质与生长的影响

在室内构建硝化型生物絮凝系统过程中不用药、添加益生菌和零换水条件下,采用300、600、900尾/m33种养殖密度,通过90 d海水养殖试验,探索了密度对该养殖模式下凡纳滨对虾生长性能与水质的影响以及养殖的合适密度。结果表明:在构建硝化型生物絮凝系统过程中,随密度增加水质逐步下降,如BFT900组的DO由8. 21 mg/L降至3. 34 mg/L,p H由8. 24降至6. 75,TAN由0. 08 mg/L升至1. 64 mg/L,NO2--N由0. 10 mg/L升至10. 80 mg/L,NO3--N由0. 54 mg/L升至153. 70 mg/L,上述各组指标差异显著(P 0. 05),硝化型生物絮凝系统转化成功后,各组水质指标均处于对虾生长合适范围;存活率随密度增加而下降,BFT300、BFT600和BFT900这3个处理组存活率分别为84. 59%±8. 83%、74. 26%±6. 66%和54. 95%±4. 23%,3组之间存在显著差异(P 0. 05);养殖结束时,对虾的平均体长和体质量随密度增加而降低,BFT300组的对虾平均体长和体质量显著高于BFT600和BFT900组(P 0. 05);养殖产量BFT600组最高,为(5. 45±0. 48) kg/m3,与BFT900组差异不显著(P 0. 05),但显著高于BFT300组产量[(4. 08±0. 63) kg/m3];饵料系数随密度增加而升高,其中BFT300和BFT600组差异不显著(P 0. 05),但均显著低于BFT900组的饵料系数(1. 82±0. 62,P 0. 05)。据养殖综合效果和生产效益,构建硝化型生物絮凝系统过程中海水养殖凡纳滨对虾可据自身条件,养殖密度可参考300～600尾/m3确定。

Effects of stocking density on water quality and growth of Litopenaeus vannamei during construction of nitrifying biofloc system

Three stocking densities from 300 ind/m³ to 900 ind/m³ were applied under the conditions of non-drug use, adding probiotics and zero water exchange during the construction of nitrifying biofloc system, and the effects of stocking densities on water quality and growth of Litopenaeus vannamei and the suitable density of culture were analysed by ninety day period of indoor seawater culture. The results show that:In the process of constructing nitrifying biofloc system, the water quality of gradually declined with increasing density. For example, the DO of the BFT900 group dropped from 8.21 mg/L to 3.34 mg/L, pH from 8.24 to 6.75, TAN rose from 0.08 mg/L to 1.64 mg/L, NO₂^--N from 0.10 mg/L to 10.80 mg/L, NO₃^--N from 0.54 to 153.70, rose the differences of the above indexes in each group were significant(P<0.05). After the transformation of nitrifying biofloc system was successful, the water quality indexes of each group were in the suitable range for shrimp growth; The survival rate decreased with increasing density. The survival rates of the three treatment groups (BFT300, BFT600 and BFT900) were 84.59%±8.83%, 74.26%±6.66% and 54.95%±4.23% respectively, and there was a significant difference among the three groups(P<0.05); At the end of culture, the average length and weight of shrimp decreased with increasing density. The average length and weight of shrimp in group BFT300 were significantly higher than those in groups BFT600 and BFT900(P<0.05); The highest yield of BFT600 groups was (5.45±0.48) kg/m³, but there was no significant difference with group BFT900 (P>0.05), but the yield was significantly higher than that in group BFT300[(4.08 + 0.63) kg/m³], and the feed coefficient rate increased with the increase of density, and there was no significant difference between BFT300 and BFT600 groups(P>0.05), but they were significantly lower than those in group BFT900 (1.82 + 0.62)(P<0.05). According to the comprehensive effects of culture and the benefit of production, 300-600 ind/m³ could be the reference density range for Litopenaeus vannamei indoor seawater culture based on practical situation during the construction of nitrifying biofloc system.