水位深度对工厂化流水养殖大菱鲆生长的影响

为探讨水深对工厂化流水养殖水环境的影响,本实验将9 000尾初始体质量为141.62±24.47 g的大菱鲆(Scophthalmus maximus)按照低水深(20 cm)、中水深(40 cm)、高水深(60 cm)条件分为3个不同养殖水深组,实验周期为80 d。实验期间,跟踪检测长期和特定时期(投喂后8 h内)不同养殖水深水体中总氨氮(TAN)、亚硝酸盐(NO₂^--N)、固体悬浮物(SS)、化学需氧量(COD)等参数,并在实验结束时对大菱鲆成活率、体质量、饲料系数水平进行测量。研究表明,水池内水流速度与水深呈负相关,但各组间无显著性差异。高水深组的固体悬浮物含量显著(P<0.05)低于其他两组,低水深组的化学需氧量显著(P<0.05)低于其他两组,各水深组中氨氮、亚硝酸盐都在大菱鲆幼鱼安全浓度范围内,且无显著性差异。在投喂后,固体悬浮物含量在各水深组中呈先升高后降低趋势,其中低水深组波动最大。氨氮含量在投喂后3 h开始上升,其中低水深组涨幅最大。各水深组中化学需氧量随着投喂时间延长而逐渐积累,而亚硝酸盐含量基本保持不变。实验结束,低水深组中大菱鲆增质量率、特定生长率、体质量变异系数均显著(P<0.05)高于高水深组,而存活率、肥满度、饲料系数在各组之间没有显著差异。研究结果显示,增加水深有利于提高养殖水环境水质恶化的缓冲能力。在保证养殖系统水质指标安全的前提下,低水深在大菱鲆工厂化流水养殖中是一个可行的方案。

Effect of water depth on the growth of turbot (Scophthalmus maximus) in factory flow-through aquaculture

To explore the effect of water depth on the water environment of factory flow-through aquaculture, 9 000 turbot with an initial collective body mass of 141.62±24.47 g were divided into three different culture depth groups according to the low (20 cm), medium (40 cm), and high (60 cm) water depths. The three water depth groups of turbot were subjected to an 80-day experiment involving periodic tracking and detection of total ammonia nitrogen (TAN), nitrite (NO₂^--N), suspended solids (SS), and chemical oxygen demand (COD). The substances in the aquaculture pool were measured for a long period and a specific period (within 8 h after feeding); the survival rate, body weight, and feed conversion ratio level of the turbot were also measured, but only once, which was at the end of the experiment. The study showed that the water flow rate in the pool was negatively correlated with water depth, but the difference between the groups was insignificant. The high water depth group had significantly (P<0.05) lower solids in suspension than the other two groups, while the low water depth group had significantly (P<0.05) lower COD than the other two groups. There was no significant difference in the levels of TAN and NO₂^--N in all water depth groups, which were within the safe concentration range for turbot juveniles. After the feeding time, the suspended solid contents in each water depth group showed a tendency to rise first and then decrease, with the greatest fluctuation seen in the low water depth group. The TAN content started to increase 3 h after feeding the turbot, with the greatest increase also recorded in the low water depth group. With the prolongation of feeding time, COD gradually accumulated in each water depth group while the NO₂^--N content remained unchanged. At the end of the experiment, the weight gain rate, specific growth rate, and coefficient of variation of body weight of turbot in the low water depth group were found to be significantly (P<0.05) higher than those in the high water depth group while the survival rate, condition factor, and feed conversion ratio were not significantly different among the groups. The results of the study showed that increasing the water depth was beneficial to improving the buffering capacity of water quality deterioration in the aquaculture environment. Under the premise of ensuring the safety of water quality indexes in the culture system, low water depth is a feasible solution in turbot factory flow-through aquaculture.