This paper addresses the limitations of traditional water quality detection equipment in aquaculture, such as restricted detection range and insufficient depth, by designing a water quality detection robot and conducting structural dynamics and fluid dynamics analyses to verify the feasibility of the proposed design. First, the robot’s structural design and modeling were carried out, and the electronic cabin was subjected to static strength verification using the finite element method. Second, based on CFD, RANS and RNG k-ε turbulence models were used to analyze the robot's straight-line motion performance at speeds ranging from 0.2 to 1.0 m/s. Finally, overlapping grid technology was applied to explore the robot’s variable-speed motion characteristics. The results show that at a depth of 100 meters, the maximum equivalent stress in the electronic cabin is 50.70 MPa, with a maximum deformation of 0.0763 mm, which meets the pressure resistance requirements. Under straight-line motion, the hydrodynamic coefficients (、、、 and ) were −34.75, −37.54, −82.81, −71.16, and −93.47, respectively. In the variable-speed motion state, the corresponding inertia hydrodynamic coefficients (、 and ) were −7.32, −24.25, and −22.53, respectively. This study not only provides a novel equipment with underwater mobile detection system capable of full-range water quality monitoring,  but also offers data support for the structural optimization and motion control strategies, advancing its practical application in the field of water quality detection.

The height of the mooring point significantly affects the platform's hydrodynamic characteristics and structural stress, thereby impacting its stability. This study uses ANSYS to investigate the hydrodynamic and structural stress features of a semi - submersible aquaculture platform under different mooring point heights. The results indicate that higher mooring points lead to greater platform motion responses, especially in terms of increased tilt angles, which negatively affect platform operation and stability under extreme sea conditions. The lowest mooring point (P1) experiences higher mooring forces and stress but remains within acceptable limits, with the smallest motion response, making it favorable for platform operation and recommended as the ideal mooring point. Further analysis was conducted on the impact of different wave periods and load directions on platform motion and stress. When only subjected to wave action, the mooring force and stress show low sensitivity to the wave period, while horizontal displacement and heave increase with the wave period. Under combined wave - current action, the trends are opposite to those observed under pure wave action. The mooring force is maximized and platform displacement minimized when the load direction is 0°, while at load directions of 15° and 30°, two mooring chains share the load, resulting in reduced mooring forces, heave, and stress, while horizontal displacement increases. The findings provide valuable insights for the design and optimization of mooring heights for semi - submersible aquaculture platforms.

 The high humidity environment in aquaculture workshops reduces the service life of workshop engineering and facilities. The high - humidity environment in aquaculture workshops present a significant challenge to equipment durability, frequently resulting in metal corrosion and mold growth. In particular, most industrial aquaculture workshops are steel - structured. Condensation on the steel frames leads to corrosion of the steel structures, which not only affects the aesthetics and service life of the workshops but also causes pollution to the aquaculture water quality. However, there is a lack of research on the temperature and humidity distribution and condensation under winter operating conditions in actual aquaculture workshops. This study provides a combined temperature - humidity control strategy for aquaculture workshops in winter, reducing the humidity in the workshop and the operating energy consumption of the ventilation system effectively. The accuracy of the numerical model was verified in this study through actual measured data of thermal environment in the experimental platform of aquaculture workshop. Thermal and humid environment and condensation in an aquaculture workshop in the condition of natural ventilation, mechanical ventilation and mechanical ventilation combined with heating are being investigated, and environmental control measures is proposed. The appropriate relative humidity range for aquaculture workshops is 60% to 80%. The study shows that the humidity of workshop and condensation on the inner wall can be reduced in the condition of mechanical ventilation. In the condition of mechanical ventilation combined with heating, indoor temperature can be increased uniformly, humidity can be reduced effectively in the workshop in winter, and heat consumption and operating costs can be reduced. The temperature and humidity monitoring points in the workshop are located at a height of 3 - 4 meters, providing a basis for the temperature and humidity monitoring positions in industrialized aquaculture. Intermittent ventilation for 23 minutes can achieve the effect of low - energy - consumption dehumidification. By adopting total heat recovery of thermal-humid air, through calculating the total heat recovery of mechanical ventilation in the actual workshop in winter, the heat recovery efficiency reaches 71.7%. The conclusions of this study have laid a research foundation for the dehumidification and energy - saving design of the air - conditioning system in industrialized aquaculture workshops, as well as the intelligent control of temperature and humidity.

To address issues like seedling blockage and damage during the falling and clamping processes in the development of mechanized kelp seedling clamping equipment, this study measured the biomechanical parameters of suitable - period kelp seedlings (Saccharina japonica) to obtain the mechanical parameters and deformation patterns of their stems and leaves under external forces. The structural composition of kelp seedlings was introduced, and their biological characteristics were measured. A texture analyzer and a friction coefficient analyzer were used to measure the mechanical properties of kelp seedlings, and discrete element simulations using EDEM verified the compression characteristics of kelp seedlings. Results showed that the tensile strength of kelp seedling stems ranged from 0.67 to 0.79 MPa, their shear strength from 1.95 to 2.23 MPa, and their compression recovery from 0.43 to 0.46. For kelp seedling leaves, the tensile strength was between 0.52 and 0.71 MPa, the shear strength between 1.12 and 1.74 MPa, and the compression recovery between 0.03 and 0.06. The tensile and shear strengths of kelp stems and leaves decreased with increasing loading speed, while the compressive recovery increased. Among stainless steel, rubber, and silicone, the friction coefficient between kelp seedlings and silicone was the highest when the normal force and loading speed were constant. The error between the simulated and measured radial compression values of kelp seedling leaves using EDEM was 8.2%. These findings offer data and theoretical support for optimizing the design of kelp seedling clamping equipment.

In order to calibrate the discrete element simulation parameters of fish pellet feed and analyze the influencing factors of repose angle of fish pellet feed, this paper measured the repose angle of fish pellet feed based on stacking experiment. Taking Tongwei 150 model pellet feed as the research object, the funnel method, cylinder lifting method and suction plate method were used to realize the formation of the repose angle, and MATLAB software was used to process the accumulation image to determine the boundary contour of pellet feed. Plackett-Burman test was used to screen out three significant influencing factors: the static friction coefficient between feed and feed, the restitution coefficient between feed and feed, and the rolling friction coefficient between feed and feed. Finally, Box-Behnken test was used to construct the regression model of repose angle and significant influencing parameters. The optimal simulation parameters were determined by Design Expert optimization as the recovery coefficient between feed and feed is 0.28, the static friction coefficient between feed and feed is 0.31, and the rolling friction coefficient between feed and feed is 0.14, among which the static friction coefficient between feed and feed and its quadratic term have the greatest influence on the repose angle of granular feed. The experimental results provide a reference for the discrete element parameter calibration of fish pellet feed and the design of feed delivery and throwing equipment.

Semi-submersible platforms face risks of mooring failure and motion instability caused by the combined action of waves and currents in exposed sea conditions. To verify the hydrodynamic performance of a retractable aquaculture platform, physical model tests were conducted to evaluate its behavior under three typical operational conditions: maintenance, floating, and seabed-resting. A 1:75 scale model was used to measure the platform’s six-degree-of-freedom motion responses and the dynamic characteristics of mooring line tensions. The results show that under maintenance and floating conditions, the combined action of waves and currents leads to the maximum mooring forces, while different load combinations have little impact on the platform’s motion. The wave period significantly affects mooring forces and pitch motion but has a minor influence on linear displacements. Under the combined action of waves and currents, mooring forces and linear displacements increase with wave period, whereas the opposite trend is observed under pure wave conditions. In the seabed-resting condition, the platform’s surplus weight provides strong resistance to sliding and overturning, with negligible motion and mooring forces. A comparison of the platform’s dynamic responses under maintenance and floating conditions reveals that under pure current or combined wave-current conditions, increasing the draft heightens mooring forces and exacerbates pitch motion while limiting linear displacements. In contrast, under pure wave conditions, increasing the draft reduces motion responses and mooring forces. The study confirms that the stability of the six-point mooring system and the strength of the mooring chains meet the design requirements, providing a basis for platform construction.

This study aimed to construct an integrated aquaponics system combining Litopenaeus vannamei and Beta vulgaris var. cicla L, and evaluate its potential for nitrogen/phosphorus removal and resource utilization in aquaculture wastewater treatment. The system's effectiveness was investigated through monitoring water quality parameters (turbidity, NH₄⁺-N, NO₃⁻-N, NO₂⁻-N, TN, TP), assessing plant and shrimp growth patterns, and analyzing microbial community dynamics. Results demonstrated that the system achieved a maximum turbidity removal efficiency of 66.9 %. Peak removal efficiencies reached 68.6 % for NH₄⁺-N and 86.0% for NO₃⁻-N during mid-operation, while NO₂⁻-N concentrations remained stable at 0.10-1 mg/L. Both Beta vulgaris var. cicla L and Litopenaeus vannamei maintained normal growth, with the plants assimilating 20.6% of total nitrogen input and 15.4 % of phosphorus input. Microbial analysis revealed that Beta vulgaris var. cicla L promoted enrichment of functional microorganisms responsible for nitrogen and phosphorus removal. The system exhibited excellent nutrient removal performance mediated by synergistic plant-microbial interactions, providing a novel approach for resource utilization of aquaculture wastewater. These findings highlight the practical significance of shrimp-vegetable symbiosis systems in sustainable aquaculture wastewater management.

Offshore aquaculture has developed rapidly in recent decades. As the most common aquaculture equipment, fish cages are widely used in the world. In order to further adapt to the harsh environment and improve the efficiency of aquaculture, a variety of large scale aquaculture cages combined with traditional marine engineering structures have also emerged. Vessel-shaped fish cage is a new type of large aquaculture structure, composed of steel floating body, net, steel frames and mooring lines, etc. Different from the conventional platform and fish cage, vessel-shaped fish cage has a large number of nets, which will affect fish cage motion and mooring response, furthermore increase economic and ecological risks. In this study, a time-domain coupling analysis method is developed to calculate the dynamic response of large floating cages in waves. Firstly, the three-dimensional potential flow theory is employed to determine the hydrodynamic coefficients of floating body, including added mass, potential damping coefficients and first order wave excitation force RAO. Subsequently the state space method is used to simulate the radiation load of floating body, the Morison equation is used to solve the hydrodynamic loads on slender structures (including steel frame, mooring line and net). Then, the coupled whole cage motion equation is established in time domain. By numerical method, influence of 3 different net models (no net, rigid net, flexible net) and net solidity ratios on motion and mooring responses were studied respectively. The results show that net increases the surge motion with 26%, but the heave and pitch motion are weakened due to the net damping effect. Additional, damping effect of flexible net is more obvious than that of rigid net. An increase of mooring line tension due to the net influence is also observed. This study can provide engineering reference and design basis for large fish cage in the concept and basic design stage.

The continuous accumulation of nitrogen and phosphorus during zero water exchange biofloc culture is difficult to deal with, while floating duckweed (Lemna minor) is regarded as a plant with good water treatment ability, and in view of its aquaculture benefits as a feed supplement, so in order to better explore the duckweed-biofarming system for P. vannamei, the present study was set up to investigate the floating duckweed group (DG) and control group (CG) for a 45-day experiment with P. vannamei . At the beginning of the experiment, 40 g (wet weight) of duckweed was placed in the net box of GD. Fresh duckweed was fed every day in addition to the normal feed, and the amount of feed was adjusted according to the body weight of P. vannamei measured every week. Results indicated that DG achieved significantly lower levels of nitrate nitrogen (NO3--N), total nitrogen (TN), phosphates (PO43--P), and total phosphorus (TP) by 13.7%, 11.6%, 12.5%, and 11.8%. The growth metrics in DG were all significantly higher than those in CG (P < 0.05). The crude ash, crude fat, and crude protein of the shrimp in DG were (2.37±1.13)%, (2.48±0.35)%, and (19.63±0.64)%, showing significant differences compared to CG (P < 0.05). The levels of ASP, Gly, Met, Leu, Lys, and Arg in DG were also significantly different from those in CG (P < 0.05). The muscle hardness, chewiness, and water-holding capacity of the P. vannamei in DG were significantly higher than those in CG (P < 0.05). The enzyme activity tests indicated that the shrimp in the DG exhibited a significant enhancement in antioxidant and digestive capacities (P < 0.05). Based on these findings, incorporating duckweed in biofloc shrimp systems can purify water and enhance the growth performance, muscle quality, antioxidant capacity, and digestive enzyme activities of P. vannamei.

In order to study the effects of different water spinach (Ipomoea aquatica) floating bed coverage ratios in aquaponic systems on the feeding rate and growth performance of Nile tilapia (Oreochromis niloticus), four experimental groups were designed: a control group with 0% coverage (C0), and three aquaponic groups with 20% (C2), 30% (C3), and 40% (C4) coverage ratios. Each group contained three replicates. Feeding rates were calculated every 7 days. After 35 days of rearing, growth indices and serum antioxidant parameters were measured. Results showed no significant differences in feeding rates among groups during the 7th days and 14th days (P>0.05). On the 21st days, aquaponic groups exhibited significantly higher feeding rates than the control (P<0.05). On the 28th and 35th days, feeding rates followed the order C4 > C3 > C2 > C0 (P<0.05). At the end of the experiment, all performance indicators in the aquaponic groups surpassed those of the control group,and with the increase of the floating bed coverage rate, the weight gain rate and specific weight gain rate of tilapia in each group increased, the activities of serum antioxidant enzymes (CAT, GSH-PX) enhanced, the total antioxidant capacity (T-AOC) increased, and the content of malondialdehyde (MDA) decreased. Considering the feeding rate and growth performance indicators of tilapia in each group, it can be concluded that the aquaponic group with a 40% floating bed coverage rate had the best rearing effect within the experimental range.

The land-based elevated round pond culture model has garnered significant attention in intensive aquaculture in recent years due to its advantages of land and water conservation and controllable farming environments. To evaluate its impact on the comprehensive quality of fish, this study focused on juvenile hybrid snakehead "Male Snakehead No.1", conducting a 365 day comparative farming experiment between an intensive land based elevated round pond group and a traditional pond culture group. post experiment analyses included growth indicators, muscle conventional nutrients, mineral elements, amino acid composition, and fatty acid content. Results revealed that in terms of growth,the intensive group exhibited higher weight gain rate, specific growth rate, and lower feed conversion ratio compared to the pond group, though differences were not statistically significant (P> 0.05). The intensive group showed a significantly higher crude fat content (P<0.01) and no difference in protein content (P>0.05). The intensive group had significantly higher calcium levels (P<0.05) but significantly lower zinc, selenium, iron, and sodium levels (P<0.05). Amino acid analysis identified 18 amino acids in both groups: the intensive group showed significantly lower total amino acids (TAA), essential amino acids (EAA), non-essential amino acids (NEAA), and umami-associated amino acids (DAA) (P<0.05). However, both groups had EAA/TAA ratios exceeding 40%, indicating high-quality protein. The intensive group detected 16 fatty acids, with significantly higher saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids (P<0.05) than the pond group, including unique components like EPA. The study concludes that land-based elevated round pond culture enhances muscle fat and functional fatty acid content but requires feed fortification to optimize mineral and amino acid balance. These findings provide insights for refining aquaculture strategies and improving aquatic product nutritional value.

To address the issues of data tampering, low credibility, and high on-chain storage pressure in aquaculture, this study constructs a blockchain-based data storage and traceability model for aquaculture. The model adopts a hierarchical storage strategy, where unstructured data such as videos and images generated in aquaculture are stored in IPFS, with only their hash addresses recorded on the blockchain. Additionally, encryption techniques are integrated to enhance data security. For structured data collected by sensors, a batched on-chain mechanism is designed, and data compression algorithms are introduced to reduce on-chain storage costs. Meanwhile, smart contracts are employed to enable automatic data verification. Using pufferfish aquaculture data as an example, the model is implemented and tested on a Hyperledger Fabric consortium blockchain. The results demonstrate that the proposed blockchain-based data storage and traceability model effectively ensures reliable traceability of aquaculture data. The value density of on-chain data is improved by approximately 91.6%, the transaction throughput reaches up to 300 TPS, and the average transaction latency is 0.5 seconds. These results indicate that the model significantly alleviates on-chain storage pressure and meets the traceability and storage requirements of aquaculture data.

To address the environmental pollution caused by the untreated discharge of laver processing wastewater and the inadequacy of traditional solid-liquid separation devices due to the unique adhesiveness of residual algae and impurities, a solid-liquid separation device for laver processing wastewater was developed. The working principle of this device was briefly described, and the structural dimensions of its core components were designed and calculated. A prototype was assembled for performance testing. With the separation rate and adhesion rate of laver processing wastewater as evaluation indices, and considering roller brush speed, filter mesh aperture, and backwashing movement speed as factors, a three-factor, three-level Box-Behnken experimental design method was used to conduct a quadratic orthogonal combination experiment. The results indicated that the optimal operating parameters were a roller brush speed of 476.28 r/min, a filter mesh aperture of 0.32 mm, and a backwashing movement speed of 0.007 m/s. Under these conditions, prototype testing achieved a separation rate of 84.12% and an adhesion rate of 4.71%, with no significant precipitates or suspended solids observed in the treated wastewater, meeting the requirements for solid-liquid separation. The study demonstrates that this solid-liquid separation device exhibits good separation performance, significantly reducing the risk of water and soil pollution from direct wastewater discharge and mitigating eutrophication issues, indicating promising prospects for widespread application.

The phenomenon of oxygen deficiency is common in intensive aquaculture and live fish transportation, and has become an increasingly important issue in the aquaculture industry. The effects of hypoxic stress on water quality, biochemical parameters, and tissue structure during the transport of Siberian hybrid sturgeon (♀Acipenser baerii × ♂Acipenser schrenckii) larvae were investigated. The hybrid sturgeon larvae were placed in environments with dissolved oxygen concentrations of 2.5 ± 0.5 mg/L and 7.5 ± 0.5 mg/L for simulated transportation. Sampling was conducted before transport (0 h) and at 3, 6, 9, and 12 hours post-transport. The results showed that after 12 hours of transport, the survival rate of larvae in the hypoxic group was 54%. The serum cortisol (COR) concentration, liver alkaline phosphatase (AKP) and acid phosphatase (ACP) activities were significantly higher than those before transport (P<0.05). Serum glucose (GLU) levels peaked at 6 hours post-transport. Liver malondialdehyde (MDA), glutathione (GSH) content, and superoxide dismutase (SOD) activity were significantly higher than those in the normoxic control group (P<0.05). The liver antioxidant capacity (T-AOC) and lysozyme (LZM) activity in the hypoxic group exhibited a trend of initial decrease followed by an increase. After 12 hours of transport, the muscle glycogen content in the hypoxic group was significantly lower than that in the normoxic control group (P<0.05), while lactic acid levels peaked at 3 hours. More severe tissue damage was observed in the liver of hypoxic group larvae after 12 hours of transport. The study indicates that hypoxic stress during transportation affects juvenile fish survival rates, water quality, and other parameters, leading to oxidative stress responses and exacerbating liver tissue damage.