*2.2. Experimental Procedures*

In this experiment, the ship adopted flow-through systems where the aquaculture water was taken from 4 m underwater. The systems were carried out by water intake from the bottom of the ship and drainage from the starboard side. During the culturing period, the water change rate of the tank was maintained 16 times per day, and water flow was maintained at 0.2–0.4 m/s. The oxygen cone pressure method was adopted to dissolve pure oxygen into the breeding water to keep the dissolved oxygen above 8 mg/L, and no air was added in the breeding chamber. The light intensity was controlled at 300–500 Lux, and the photocycle was set to 12D: 12L from 5:30 am to 5:30 pm. In this study, the commercial special feed (main nutrients: crude protein 42%, crude fat 6%, crude fiber ≤ 5%, ash ≤ 18%, moisture ≤ 12%, total phosphorus 1.2%, lysine 2.2%) was the feed that was used for large yellow croakers. The fish were feed once in the morning and evening (6:00, 17:00). The daily standard feeding amount was 1.2–1.5% of the body weight of the fish and adjusted at any time according to the changes in water temperature, weather, and water quality, feeding behavior and residual bait situation, to reduce the residual bait amount as far as possible. Every two weeks, the underwater robot was used to clean the bottom of the tanks to ensure the cleanliness of the culturing environment. During ship culture, the noise pressure level of the tanks was recorded between 119–125 dB under mooring conditions and 132–134 dB under sailing conditions by using a hydrophone (C55, Cetacean Research Technology, Seattle, Washington, DC, USA). The planned experimental period was from June to August 2021. The caged group of large yellow croakers were kept according to cage culture rules for normal feeding.
