养殖密度对循环水系统中大菱鲆(Scophthalmus maximus)生长的影响

Effects of Stocking Density on the Growth and Physiology of Adult Turbot and Changes in Water Quality

将初始体重为(580.9±44.65)g的大菱鲆成鱼按照低密度A组14.30 kg/m2、中密度B组20.49 kg/m2、高密度C组31.32 kg/m2的标准分为3个不同养殖密度组,并放养于循环水养殖系统中120 d,同时对大菱鲆成活率、体重差异、饵料系数、溶菌酶水平及养殖水体中总氨氮(TAN)、亚硝酸氮(NO2--N)、COD浓度的变化进行测定。研究表明,实验结束时A、B、C三组大菱鲆养殖密度分别达到30.09、41.30、60.07 kg/m2,各实验组成活率都在95%以上。大菱鲆养殖密度对增重率的影响主要体现在研究前期,并且随着养殖密度的增加,各实验组体重差异度出现显著变化(P<0.01)。大菱鲆A、B、C组的饵料系数分别为0.73、0.75、0.82,与养殖密度呈正相关。研究开始第5天,高密度组大菱鲆溶菌酶水平升高,20 d后血液溶菌酶水平逐渐降低,40 d之后显著低于低密度组。研究期间系统运行稳定,循环水养殖大菱鲆的不同密度对系统各项水质指标总氨氮(TAN)、亚硝酸氮(NO2--N)、COD浓度的变化有显著影响(P<0.05)。研究结果显示,随着养殖密度的升高,各项水质指标显著升高,但高密度组各项水质指标均未超过渔业水质标准所规定的浓度。

To investigate the effects of various densities on the growth, physiology and water quality of adult turbot in a recirculating aquaculture system, the adult turbots with the initial average weight （580.9±44.65） g were cultivated at one of the following three stocking densities：low （14.30 kg/m^2, Group A）, medium （20.49 kg/m^2, Group B）, and high （31.32 kg/m^2, Group C） for 120 days. The survival rate, weight change, food coefficient and blood lysozyme level, as well as the changes in total ammonia （TAN）, nitrite nitrogen （NO2^- -N）, and COD in aquaculture water were measured. The results showed that the stocking densities of A, B and C group were 30.09 kg/m^2, 41.30 kg/m^2 and 60.07 kg/m^2, respectively at 120 days. The survival rates of three groups were all over 95%. The net weight gain in each group varied significantly （P〈0.01） with the highest in Group C. Feed conversion rates （FCR） of cross the three groups were 0.73, 0.75 and 0.82, respectively, which were positively associated with stocking density. Blood lysozyme level in Group C was increased at 5 d; it began to decline at 20 d and then decreased markedly at 40 d compared with that in Group A （P〈0.01）. During the entire experiment, the recirculating aquaculture systems were stable and the stocking densities had significant effects on the TAN, NO2--N and COD of water quality index （P〈0.05）. The increase of the stocking density significantly increased water quality indexes;however, it did not exceed the fishery water quality standards.