Ship aquaculture platforms are expected to become a meaningful way to expand offshore farming. The growth performance and nutritional composition of the large yellow croaker reared in an offshore ship aquaculture system and nearshore traditional cage system was evaluated in this study. The results showed that the aquaculture ship could effectively avoid the harsh environment such as typhoons and red tides. The test large yellow croaker adapted to the ship culture system in a short time. No serious stress events occurred during the whole rearing process. During the culture experimental period, the fish fed normally, and disease was controlled. The aquaculture ship has good environment conditions during breeding with a water temperature of 21.5–28.5 °C, salinity 20.7–31.8‰, pH 7.6–8.4, dissolved oxygen 7.2–12.8 mg/L, ammonia nitrogen < 0.08 mg/L, and the number of bacteria and vibrio in water were 1.2 ∗ 10³–1.6 ∗ 10³ CFU/mL and 1.2 ∗ 10²–1.8 ∗ 10² CFU/mL, respectively. The survival, weight gain rate, and monthly weight gain of the large yellow croaker in the ship were 99.02%, 41.48%, and 67.52 g, respectively, which were significantly higher than those of cage culture. The crude protein content of the large yellow croaker raised in the ship was significantly higher than that in the cage group, and the crude fat content was significantly lower than that in the cage group. These results indicated that the growth performance and nutritional composition of the large yellow croaker reared in offshore ship were better than those of the fish in the cage. These findings enhanced our understanding of an offshore ship aquaculture model of large yellow croaker.

To explore the effect of density on large yellow croaker (Larimichthys crocea) under intensive aquaculture conditions and determine the appropriate culturing density, this study investigate the effects of different stocking densities on the nutritional composition, stress, and immune levels of large yellow croaker. Through a long-term aquaculture experiment, conducted under flow-through conditions of intensive aquaculture, three initial density groups were set: a low density group [LD], 4.92 kg/m³; a medium density group [MD], 7.56 kg/m³; and a high density group [HD], 10.08 kg/m³, for a 150-day rearing trial. Large yellow croaker were fed to satiation twice daily (6:00, 17:00). At the end of this trial, the final densities were 10.38 ± 0.50, 14.41 ± 1.06, and 18.71 ± 0.99 kg/m³ in the LD, MD, and HD groups, respectively. The results showed that the growth performances were adversely influenced by a high stocking density. Levels of cortisol in serum, superoxide dismutase (SOD) and catalase (CAT) in liver, Na⁺-K⁺ ATPase and Na⁺-K⁺ ATPase gene in gills, and heat shock protein (HSP70/90) genes and glutathione S-transferase (GST) genes in the liver significantly increased under HD treatment. Results of immune response analyses showed that there was a clear decrease in immunoglobulin M (IgM), complement component 4 (C4), and lysozyme (LZM) in serum, lysozyme (LZM) genes, tumor necrosis factor-alpha (TNF-α) genes and interleukin-1β (IL-1β) genes in the head kidney of large yellow croakers reared in the HD group. An obvious increase in free amino acids and fatty acids in the muscle of large yellow croakers reared in HD group was also observed. Overall, this study showed that the optimal final culturing density of large yellow croaker under flow-through systems should be between 14.41 kg/m³ and 18.71 kg/m³ to improve aquaculture efficiency and product quality.

The present study conducted a Life Cycle Assessment (LCA) to evaluate the carbon emissions associated with large yellow croaker farming on Aquaculture Vessel “Conson No. 1”. The functional unit considered was 1 kg of fresh large yellow croakers delivered to a wholesaler. The life cycle of large yellow croaker farming on the aquaculture vessel was divided into five processes: feed production (FP), ship construction (SC), fingerling breeding (FB), adult fish farming (AF), and fish distribution (FD). Results showed that the carbon footprint (CF, kgCO₂e/kg LW) for the complete life cycle amounted to 6.2170 kgCO₂e/kg LW, while the CF per unit economic value of “Conson No. 1” large yellow croaker was estimated at 31 gCO₂e/CNY. Among all processes, AF and FP had the highest CF contribution rates at 69.30% and 24.86%, respectively. Notably, energy consumption by aquaculture equipment on board emerged as the primary contributor across all sources of CF comparative analysis demonstrated that the CF of marine fish farming on the aquaculture vessel was lower than that of closed aquaculture systems’ average level and it was a viable option for implementing low-carbon aquaculture in the deep sea. In order to reduce energy consumption and promote a low-carbon economy in aquaculture vessels, several suggestions were proposed, including adjusting energy structure, enhancing energy efficiency, improving feed ratio, and optimizing feeding methods.

To maximize the utilization of ocean resources, shorten the return period of investment and directly supply energy to the fishing cage, this paper performs a preliminary study for a state-of-the-art concept integrating a floating offshore wind turbine with a fishing cage. An octagonal semisubmersible rigid fishing cage with a slack catenary mooring system is designed to match the NREL 5 MW offshore baseline wind turbine. Combined with the blade pitch controller, fully coupled aero-hydro-elastic-servo-mooring simulations are performed through FAST and AQWA to explore the dynamic performance of the integrated system. Free decay conditions, uniform wind with irregular and regular waves, and turbulent wind with irregular waves are tested. The results showed that the integrated system works normally at the operating conditions and exhibits different dynamic characteristics for various scenarios. Additionally, the study on the influence of mooring line length indicates that the increasing line length can significantly affect the cage surge motion and the maximum and mean values of the upwind line tension at fairlead. Specifically, the maximum surge motion with a 924-m-long line is 404.8% larger than that with an 880-m-long line. When the line length increases by 5%, the maximum and mean line tensions decrease by 45.7% and 47.7%, respectively, while when the line length increases by 10%, the maximum and mean line tension decrease by 52.9% and 54.2%, respectively. It should be noted that the main purpose of this work is to conduct a preliminary study on this integrated system, aiming to provide an idea for the conceptual design, modeling and simulation analysis of this integrated system.

The present work presents numerical research on the wake flows behind a propeller operating under three advance coefficients. Large eddy simulations are adopted to obtain the viscous flow information behind the propeller. In particular, the study highlights the comparison of the evolution characteristics and the flow physics within the propeller wakes with three advance coefficients. The predicted global force and moment coefficients and phase-average statistics of streamwise velocity agree well with the available experimental data. Compared to all other flow structures in the wake, the tip vortices are found to play the most significant role according to the results. During the pairing process of adjacent tip vortices, the tip vortices diffuse circumferentially, leading to enhanced mutual-induction effects. When the advance coefficient is low, the wake becomes distorted, and the pairing process takes place in the middle region of the flow field. As a result of their unstable motion, the four tip vortices generated by the propeller cannot be distinguished individually in the far field. Instead, they break down into smaller vortices and tend to distribute themselves uniformly in the azimuthal direction. The increase in the advance coefficient delays the pairing process. This study offers valuable insights for the design and optimization of marine propellers.

Flow velocity is a key environmental factor that affects the behavioral strategies and physiological homeostasis of fish. To study the effects of flow velocity on the behavioral changes and blood physiology of the yellow croaker, the behavioral patterns of yellow croakers in response to flow velocity stress were obtained by analyzing changes in tail wagging frequency and amplitude. Differences in blood glucose, lactate, and cortisol were compared to determine their appropriate flow rate ranges. The juvenile stage of the large yellow croaker is crucial, as environmental changes can affect the physiology of fish. Therefore, juvenile yellow croakers were selected as the experimental subjects for this study. Twenty-four healthy and uniformly sized large yellow croakers with body weights of (90.26 ± 9.91) g and body lengths of (19.91 ± 0.69) cm were randomly assigned to one control group and three experimental groups, with five fish in each group. The experimental group was set with three flow rates, namely 1 bl/s (20 cm/s), 2 bl/s (40 cm/s), and 3 bl/s (60 cm/s), with a flow rate stress duration of 1 h. The results showed that: (1) Under different flow velocities, the fish exhibited different tail wagging patterns. At low flow velocities, their tail fins exhibited a “C”-shaped swing, while at high flow velocities, their bodies exhibited an “S”-shaped swing. (2) Oscillation frequency and amplitude both increased with increasing flow velocity. At a flow velocity of 2 bl/s, the oscillation frequency significantly increased. When the flow velocity reached 3 bl/s, the oscillation amplitude significantly increased (p < 0.05). (3) Blood physiology showed significant changes with increased flow rate, and blood glucose content continuously decreased with increased flow rate, significantly decreasing at a flow rate of 2 bl/s (p < 0.05). Lactic acid and cortisol both increased with increasing flow rate, and significantly increased at a flow rate of 3 bl/s (p < 0.05). In summary, under high-flow velocity stress, significant changes occurred in the behavior and physiology of large yellow croakers, which were consistent with physiological changes in the blood. A flow rate higher than 2 bl/s can lead to intense swimming behavior, decreased blood sugar concentration, and increased lactate accumulation and stress levels. Therefore, the short-term tolerance of yellow croakers is 2 bl/s, and a flow rate of 1 bl/s is more suitable.