*2.1. Experimental Animals and Facilities*

Traditional aquaculture cages (26◦37 35 N, 119◦51 72 E) were set in Sandu Bay, Xiapu County, Ningde City, Fujian Province, China. The closed aquaculture vessel of GuoXin No. 1 was transferred to the sea areas of Ningde in Fujian province, Zhoushan in Zhejiang province, and Qingdao in Shandong province to maintain the best growth conditions.

Large yellow croaker (340 ± 10 g) were obtained from Guoxin (Taizhou) aquaculture farm in Ningde City, Fujian Province. The test fish were incubated in an indoor hatchery and cultured in open cages in the inshore waters of the inner bay. Before the experiment, according to the initial density of 12.1 kg/m3, 30,000 healthy large yellow croakers were randomly put into three 280 m<sup>3</sup> breeding tanks with 10,000 fish per tank. In addition, two traditional cages (10.5 m ∗ 7.0 m ∗ 6.0 m) were set up for the comparative test. The density of the traditional cage was subject to the actual production. The initial density of 5.06 kg/m3 was used to put 6700 large yellow croaker of the same specification per cage. The large yellow croakers spent three weeks acclimatizing to the experimental environment before the experiment officially began. A period of respite, no feeding was performed for the first three days, and the feeding rate gradually increased to the normal level as time passed.

The mid-trial ship "Guoxin 101" was transformed from an offshore bulk carrier, with a total length of 96.8 m, a type of width of 16.6 m, a displacement of 5491 t (Figure 1A,B), a power of 2 × 662 kW, and a speed of 10.5 kn. It was equipped with three nearly quadrilateral breeding tanks with a volume of about 280 m3 (Figure 1C,D; 8.8 m ∗ 7.8 m ∗ 5.15 m; the water level was 4.1 m). There was a movable awning on the upper opening. The marine aquaculture system was mainly composed of water circulation, oxygenation, illumination, sewage, and monitoring and alarm systems.

**Figure 1.** Gouxin No 101 closed aquaculture vessels. (**A**,**B**) represent overall photographs and schematic diagrams of the ship, respectively; T1, T2, and T3 are represented as the three different tanks in the ship; (**C**,**D**) are field pictures and schematic diagrams of the culture tank.
