Abstract:The yellowtail kingfish (Seriola lalandi) is a globally distributed pelagic migratory fish species. It is considered a promising species for the aquaculture industry worldwide because of its high flesh quality and fast growth. Therefore, the demand for yellowtail kingfish has increased in recent years, which has caused overfishing and a drastic decline in natural resources. Large-scale farming started in 2017 as seedlings production technology was established in China. Practice has proved that farming this species is suitable in both net cages and industrial farming systems. With the growth of the scale of farming, it is urgent to determine the key parameters, including the suitable stocking density and other factors, to establish an efficient technology for industrial farming. The stocking density of marine animals is a critical parameter in aquaculture management. A suitable density could reduce the stress level of the farmed animals, which will be beneficial to good health and rapid growth. To investigate the optimal density of yellowtail kingfish in land-based industrial farming, this study was conducted in 6 circular glass buckets for 60 d. The effective water volume of each circular glass bucket was 3 m3 , and these buckets were divided equally into three density groups: 10 fish/m3 (low-density group), 20 fish/m3 (mediumdensity group), and 30 fish/m3 (high-density group). After domestication, healthy 1 year old yellowtail kingfish [(565.83±70.22) g] were distributed into three density groups according to the density rule. The water temperature was 22–27 ℃, salinity was 29–32, and the dissolved oxygen was higher than 6 mg/L during the experiment. During this experiment, the growth performance indicators, including weight gain ratio (WGR), specific growth ratio (SGR), condition factor (K), and hepatosomatic index (HIS) were measured and calculated, and indicators, such as blood physiology (e.g., white cell number, red cell number, hemoglobin), serum biochemistry (e.g., epinephrine and cortisol content), and the non-specific immune enzyme activity of the liver and kidney tissues [e.g., activities of superoxide dismutase (SOD) and lysozyme (LZM)] were detected. The results showed that the WGR and SGR of yellowtail kingfish in medium and high-density groups were significantly lower than those in the low-density group at 60 d (P<0.05). The SGR of the low-density group at 60 d was significantly higher than that at 30 d (P<0.05). However, there was no significant difference in the SGR of the medium-density group between 60 d and 30 d (P>0.05). Moreover, the SGR of high-density group at 60 d was lower than that at 30 d. The changes in these growth performance indices indicated that the higher stocking density had been stressful to the growth of yellowtail kingfish. During the entire experiment, the contents of epinephrine and cortisol in the serum increased significantly at 30 d and 60 d with the increase of stocking density (P<0.05), whereas the contents of growth hormone (GH) and insulin–like growth factor I (IGF–I) in serum showed the opposite trend. The activities of SOD, AZM, ALT, AST, ACP, AKP, and PK exhibited a trend of increasing significantly at 30 d and 60 d with the increase of stocking density (P<0.05). The changes in these physiological and biochemical indicators showed that the higher stocking density created stress on the physiology of yellowtail kingfish. Therefore, from the perspective of growth, physiology, and production practice, the low-density group (20 fish/m3 ) is the appropriate density for the industrial farming of 1 year old yellowtail kingfish. The relative results provide a basic reference for further improvement of industrial farming technology for yellowtail kingfish.