Biofloc technology (BFT) is a promising technology for the sustainable improvement of aquaculture productivity. In BFT, maintaining an appropriate C:N ratio (10:1 ~ 20:1) by adding a carbon source promotes the growth of heterotrophic bacteria in water, heterotrophic bacterial assimilation of ammonia-nitrogen to bacterial biomass. In practical use, however, BFT system wastewater treatment functions remain limited in aquaculture. Besides, adding organic carbon also produces large amounts of suspended particulate that affects the health of aquatic animal. Therefore, it is necessary to optimize the BFT system wastewater treatment capability by using a variety of technical methods. Here, we introduce the principle of BFT and the problems in its application. The enhanced and combined methods of BFT, principles, application scopes and effects are discussed. We also highlight the effects of enhanced methods on the BFT system, including pollutants removal efficiency, microbial communities, and the growth performance of aquatic animals. The main messages from the result can be summarized as follows. Firstly, the cultivation of nitrifying bioflocs alleviates the need for organic carbon and dissolved oxygen in aquaculture systems, and reduces suspended solids. Besides, BFT reactor can cultivate high concentrations of bioflocs and improve the removal efficiency of nitrogenous compounds. Adding probiotics, microalgae, macroalgae, and substrates to BFT system improves the growth performance and immunity of aquatic animal, as well as enhance the microbial life and decomposition process, increasing the removal efficiency of nitrogen, phosphorus and organic matter. The coupled Integrated Multi-Trophic Aquaculture System, Recirculating Aquaculture System, and Aquaponics System with BFT can not only improve the nutrient use efficiency and production of aquatic animal, but also reduce the operating costs of the system. We also foresee the application of BFT would bring a change in the aquaculture mode in China. The in-depth research and application for an enhanced and combined method of BFT would further promote the sustainable development of the aquaculture industry.

With the rapid development of scallop farming in China, the country has become an important global producer of scallops. However, China's scallop fishing technology is relatively backward, presenting issues such as low efficiency, a high amount of broken scallops, and ecological damage to the seabed. Therefore, developing environmentally friendly fishing techniques and equipment is crucial for promoting the construction of scallop aquaculture-type marine pastures. This research reviews the main scallop fishing techniques and equipment both domestically and internationally, including sweeping, digging, anti-misoperation, hydrodynamic, and suction fishing methods, along with supporting mechanized shellfish unloading devices. Through comparative analysis, it evaluates the advantages and disadvantages of these technologies in terms of basic research, fishing efficiency, structural design, and ecological impact, as well as their practical application effects. Sweeping fishing is suitable for large-scale and rapid harvesting but causes significant ecological disturbance to the seabed and is prone to mistakenly capturing non-target species. Digging fishing is appropriate for collecting scallops on hard substrates, reducing environmental damage, though its efficiency is relatively low. Anti-misoperation fishing reduces the bycatch rate of non-target species, protecting marine biodiversity, but it comes with higher costs. Hydrodynamic fishing utilizes water flow to guide scallops into nets, minimizing seabed ecological impact, yet it requires precise control of water flow parameters. Suction fishing is suitable for shallow sandy substrates with minimal ecological impact but remains in the experimental stage. This article summarizes the problems in China’s scallop fishing technology and proposes future development directions. It advocates for in-depth exploration of the impact mechanisms of fishing on underwater ecosystems to provide theoretical support for reducing ecological impacts. Developing new materials and technologies to optimize existing net designs, such as using biodegradable materials and smart fibers, can reduce resource consumption and pollution. Integrating machine vision, texture simulation, and multi-sensor data fusion can achieve real-time monitoring and intelligent decision-making, improving fishing efficiency and ensuring operational safety. Through technological innovation and upgrading, the goal is to achieve coordinated development between fishery production and environmental protection, thereby promoting the healthy and sustainable development of China’s scallop industry. This research not only provides valuable reference for relevant researchers and enterprises but also offers scientific basis for policymakers to jointly advance the modernization of scallop aquaculture-type marine pastures.

 Whether in the wild or in captivity, large yellow croaker (Larimichthys crocea) may suffer from starvation. To study the effects of starvation and restoration feeding on large yellow croaker, The experiment was conducted with a sample of large yellow croaker with an initial body weight of (122.62±11.08) g and a body length of (17.90±1.04) cm. The fish were starved for0,2,6,10 or16 d (S0,S2,S4,S8,S16) and then feeding was resumed. The results are as follows: the body weights of the starved groups showed a decreasing trend, and the largest decrease was observed in group S8. After resumption of feeding, all the starved groups showed only partial compensatory growth capacity at the end of the experiment , among which the S8 and S16 groups showed lower compensatory growth capacity. Serum glucose, triglyceride, alkaline phosphatase (AKP) and acid phosphatase (ACP) tended to decrease with the extension of starvation time, and reached the lowest at 8 days of starvation. At the end of the experiment, its indicators did not recover significantly after 8d of refeeding.. In addition, cortisol concentration and superoxide dismutase (SOD) activity rose to the highest at 8 days of starvation, while the recovery was not obvious after refeeding. The intestinal tissue structure of large yellow croaker was basically consistent with its physiological and biochemical trends, and the height of intestinal villi and the thickness of muscularis propria decreased to the lowest level at 8 days of starvation, and the recovery was not obvious after re−feeding. IL-1β, IL-10 and TNF-α gene expression in the intestine increased with starvation, was highest in the S4 group and decreased after resumption of feeding. The results showed that: In summary, under the conditions of this experiment, starvation stress lasting for 8 days would have a significant effect on large yellow croaker. Therefore, in order to ensure the feeding effect, it was recommended that the length of starvation of the large yellow croaker should be controlled within 8 days..

To meet the environmental monitoring needs of marine ranching, a physical and chemical indicators and visual monitoring platform for sea cucumber bottom sowing culture environment was developed. By constructing the numerical model of the platform, the structural strength analysis of the platform is carried out. Based on the three-dimensional potential flow theory, the platform motion response model under the coupling condition of wind, wave, and current is established. The AQWA software is used to analyze the variation law of the maximum center of gravity amplitude, and the mooring system optimization is realized by optimizing the position of the guide hole and the length of the mooring line. The research shows that under the condition of ten-level wind and wave when the angles of wind, wave, and inflow are 90 °, 135 °, and 90 °, the motion range of the center of gravity of the platform reaches the maximum and is in the most dangerous state; when the position of the guide cable hole is reduced to 0.5 m underwater, the roll, pitch, and yaw amplitudes of the platform are reduced by 50.6 %, 61.7 % and 43.4 %, respectively. When the cable length is reduced to 70 m, these amplitudes are reduced by 28.4 %, 47.7 %, and 32 %, respectively. The mooring safety factor is 1.89, which meets the design requirements. To further demonstrate the accuracy of the numerical model of the platform, the motion response and mooring force of the platform were measured during the influence of typhoon ' Gaemi'. The test results show that under the coupling of wind, wave, and current, the maximum angles of roll, pitch, and yaw of the platform are − 4.829 °, − 0.934 °, and 0.610 °, respectively. The maximum measured angles at sea are − 6.399 °, − 1.329 °, and 0.774 °; the simulated and measured mooring force coefficients of the platform are 3.63 and 3.92, respectively, which are consistent with the lifting trend of the numerical simulation results. The motion response error is less than 2 °, which verifies the good safety of the platform. It provides theoretical and technical support for the development and application of marine ranching environmental monitoring platforms.

In order to effectively improve the structural damage and environmental pollution caused by bamboo and wood raft cultivation equipment in Beibu Gulf of Guangxi in the process of long-term use, and improve its ability to withstand wind and waves, the HDPE raft culture equipment was selected as the research object, taking the common 15 m long and 12 m wide single raft in Beibu Gulf of Guangxi as an example. AQWA software was used to establish a hydrodynamic analysis model, and based on frequency domain analysis and time domain analysis methods, mooring length and mooring Angle were taken as response indexes to carry out research on the hydrodynamic characteristics and motion response of raft farming equipment, and obtain the motion response and mooring tension variation rules of various degrees of freedom of raft farming equipment. The results show: Under the condition of level 7th high wind and waves, the motion response and mooring cable tension of raft culture equipment change significantly under different mooring lengths and angles. When the ratio of mooring cable length to water depth l/d =1.08 and the Angle of mooring cable is less than 30°, the motion response and mooring cable tension of raft culture equipment are smaller. The optimum mooring form is determined under this condition. Conclusion: Through theoretical and numerical simulation analysis, parameter comparison and early warning are provided for the structural state and safety of aquaculture equipment under different sea conditions, and theoretical reference is also provided for the better application of HDPE materials to raft aquaculture equipment.

The present study was conducted to evaluate the efficacy of a pollution isolation device in improving water quality in facility-based soft-shelled turtle (Pelodiscus sinensis) aquaculture. A total of 72 soft-shelled turtles, each weighing approximately 300 g, were utilized in this experiment. Two groups were established: one with a small turtle culture pond equipped with a pollution isolation device (treatment group) and another without the device (control group). Water quality parameters, including ammonia nitrogen, turbidity, chemical oxygen demand (COD), and nitrite nitrogen, were monitored and statistically analyzed. The results indicated that the ammonia nitrogen concentration in the treatment group was significantly higher than that in the control group, reaching a maximum of 108 mg/L. The average change rates for turbidity and COD in the control and treatment groups were 14.2% and 8.4%, and 39.5% and 15.5%, respectively. Over the culture period, the control group discharged 286.59 g of COD, 68.33 g of total phosphorus, and 12.32 g of total nitrogen, whereas the treatment group discharged 92.21 g of COD, 46.01 g of total phosphorus, and 5.07 g of total nitrogen. The study demonstrated that, despite the higher ammonia nitrogen concentration in the treatment group, the pollution isolation device significantly reduced the average change rates of turbidity and nitrite nitrogen and decreased the discharge of COD, total phosphorus, and total nitrogen during the culture cycle. Moreover, extending the water exchange period to 15 days effectively reduced the volume of water exchanged and the emission of pollutants. These findings suggest that the pollution isolation device is effective in isolating pollutants and significantly improves water quality in soft-shelled turtle aquaculture systems.

The sea cucumber industry is a pivotal sector in China's fishery economy, yet the insufficient mechanization level in aquaculture and fishing has become a critical bottleneck. This study systematically reviews the technological advancements in sea cucumber aquaculture and fishing equipment. It first analyzes the technical features of automatic feeding systems and automatic pool transfer machines in industrialized aquaculture, while comparing the efficiency, advantages, and limitations of various fishing methods and operational mechanisms in marine operations. Subsequently, the study highlights key technological innovations, elucidating how kinematic simulation technology optimizes equipment structures and demonstrating how underwater target recognition enhances fishing precision. Finally, three strategic development pathways are proposed: optimization of critical components in engineering aquaculture equipment, integrated innovation in intelligent fishing technologies, and establishment of equipment evaluation frameworks. The findings provide theoretical foundations and technical references for advancing automation and intelligence in sea cucumber aquaculture and fishing equipment.

With the continuous development and utilization of marine resources, the convergence of modern marine ranching and offshore wind power has become an important development direction for intensive use of sea space and improving the efficiency of marine resource utilization. This paper constructed a tidal-driven three-dimensional dual-nested high-resolution hydrodynamic model of the Bohai Sea based on the FVCOM ocean numerical model, analyzed the hydrodynamic characteristics of the combined structure of the artificial reefs and the wind power foundation, as well as the changes in the hydrodynamic environment around the wind power foundation before and after the artificial reefs placed. By validating for harmonic analysis of M2, tidal current magnitude and direction, the skill assessment parameters are above 0.81, and the model had a high simulation accuracy. The model results showed that the tidal current in the wind power area were characterized by a northeast-southwest reciprocal flow; the artificial reefs can significantly reduce the horizontal flow velocity around the wind power foundation over a wide range, with a general reduction of 8% to 15%, reaching a maximum of 32.1%; there was significant upwelling generated above the artificial reefs, upwelling near the front of the incoming flow from the wind power foundation, and downwelling near the back, so their combined structure can significantly promote vertical mixing of the ocean current. The results of the study can provide a new case reference for the convergence of marine ranching and offshore wind power.

 Fishing sonar utilizes sound waves to detect the distribution and activities of underwater fish schools. It typically employs either omni-directional transmission or directional scanning transmission methods for preliminary detection of the position of fish schools. However, there are several limitations with these traditional methods, including poor signal directivity in omni-directional transmission and uneven beam coverage in directional scanning transmission. To address these challenges, this study proposed an improved method based on rotating sector scanning, which aims to optimize the detection performance and meet the specific requirements of fishery sonar in practical fishing scenarios. This study used acoustic simulation methods to systematically analyze the factors that influence the scanning transmission performance, such as the number of sectors and the boundary angles between sectors. The performance of the proposed method was further validated through pool tests conducted under controlled laboratory conditions. The simulation results showed that the use of a four-sector rotating sector scanning transmission method effectively improves the signal directivity while maintaining a full 360° horizontal scan coverage. Specifically, the main lobe intensity was increased by 8 dB when compared to omni-directional transmission, and the maximum intensity difference within a single sector’s transmission beam was reduced to less than 1.5 dB, with the beamwidth difference kept within 2°. These results demonstrated the advantages of the proposed method in enhancing the detection capabilities of the sonar system. To further evaluate the practical performance of the system, laboratory pool tests were carried out to measure the transmission directivity between two adjacent sectors. The results from these tests showed that the proposed method improves the directivity by approximately 8 dB on average over a 64° range in front of the two sectors compared to the omnidirectional transmission. This finding suggests that the proposed design not only enhances the efficiency and accuracy of fish school detection but also helps to obtain accurate fish information in a wider range.

For factory farming environments characterized by relatively limited computing resources, enhancing identification speed and reducing model size while ensuring high accuracy has emerged as an urgent technical challenge. This necessitates the optimization of both operational efficiency and model scale to accommodate various constraints inherent in practical applications, all while maintaining a high level of accuracy. Traditional object recognition algorithms, such as those within the YOLO family, although demonstrating excellent performance across multiple application scenarios, typically depend on powerful computing platforms capable of supporting their extensive model parameters and complex computational processes. The substantial computational demands present a significant bottleneck for factory farming settings where equipment is often ill-equipped to manage 
large deep learning models; yet real-time monitoring and rapid response are essential for effective management of fish growth and health. To address this issue, existing research into lightweight models offers potential solutions. However, these approaches frequently compromise a certain degree of recognition accuracy in their pursuit of smaller model sizes and reduced computational costs. In the context of the factory farming industry, such declines in accuracy are unacceptable since precise fish monitoring directly impacts both farming effectiveness and economic viability. Consequently, there is a pressing need to explore innovative methods that can significantly reduce model complexity without substantially affecting recognition performance. In light of this necessity, we propose an innovative lightweight fish school identification model named FasterYOLOv9-Slim. This model aims to achieve efficient operation alongside a lightweight design while ensuring high precision through a series of targeted improvements and optimizations.Specifically, the FasterYOLOv9-Slim model is based on the improvement of YOLOv9 and FasterNet, aiming to solve the balance between recognition accuracy and speed through a series of innovative network architecture optimizations. First, on the basis of YOLOv9 model, FasterNet is introduced as a lightweight backbone network to replace the complex backbone structure used in the original model. The core of this change is to take advantage of the more efficient network structure of FasterNet to effectively reduce the large number of parameters and computational requirements brought by the traditional convolutional operation of the YOLOv9 backbone network, which not only significantly improves the detection speed of the model, but also reduces the burden of the model while maintaining a good recognition ability of the target, ensuring the practicality and effectiveness of the model in practical applications. Secondly, in order to further optimize the overall performance of the model, high-dimensional detector head pruning (HDPrune) is used to prune a pair of high-dimensional detector heads in the head network of the YOLOv9 model to reduce the depth of the network to reduce the amount of computation, which not only helps to speed up the operation of the model, but also effectively reduces the accumulation of interfering information in the network to ensure the stability of the model in the face of complex background. The model is stabilized in the face of complex background. Finally, the original feature fusion module RepNCSPELAN4 is improved based on partial convolution (PConv) to obtain a lighter and more efficient version of FasterRepNCSPELAN4, and combined with the advanced downsampling modules ADown and DownSimper, the neck network structure of the model is redesigned to construct a more efficient feature fusion framework. fusion framework. While reducing the computational amount, the network's ability to express features at different scales is enhanced, and the model's efficient coordination between feature extraction, fusion, information transfer, and detection head output is realized.To fully verify the effectiveness of the improvement, ablation and comparison tests are designed. In the ablation test, the effects of three key improvements, FasterNet, high-dimensional detector head pruning (HDPrune), and DFA-Neck, on the model performance are tested, and the results show that FasterNet effectively reduces the number of parameters in the model, proving its significant advantage in reducing the consumption of computational resources, while HDPrune plays an important role in weakening the accumulation of interfering information in the network, and DFA-Neck plays an important role in weakening the accumulation of interfering information in the network. plays an important role in this regard, and DFA-Neck successfully coordinates the functions of FasterNet and HDPrune in the overall network, ensuring the model's high efficiency in the process of feature extraction and information transfer. In the comparison test, the model was compared in detail with the advanced identification models of the same size in the YOLOv7, YOLOv8 and YOLOv10 series models in terms of performance, and the results showed that FasterYOLOv9-Slim achieved 34.14%, 64.02% and 22.22% significant reductions, and demonstrates excellent overall performance in terms of model size, inference speed, and recognition accuracy in comparison with state-of-the-art lightweight networks such as ShuffleNet, MobileNet, and RepViT. The study verifies the effectiveness of the FasterYOLOv9-Slim model in balancing accuracy and speed in the fish identification task under factory farming conditions with limited computational resources, and also provides valuable experience and guidance for the design and optimization of the model in similar application scenarios in the future.

The technology of waterless live transportation of aquatic products has the advantages of low carbon environmental protection, safety and high efficiency. it is more important, it conforms to the current development trend of e-commerce, meets the needs of consumers in various places for fresh aquatic products, and facilitates the implementation of the express delivery service of live aquatic products. In order to prolong the survival time and improve the survival rate of Verasper variegatus, the purpose of long-distance transportation to fully realize the economic value of fresh V. variegatus was achieved in the research process of waterless transportation technology of V. variegatus. In the long-term research on the technology of waterless preservation of aquatic products, the research group found that fasting and cold acclimation of fish before preservation and transportation can effectively prolong the survival time and increase the survival percentage of fish during transportation. At the same time, the preservation effect is affected by aquatic products, development degree, season, growth water area and low temperature tolerance. In this study, cold acclimation, vitamin C addition, anesthetics and biorhythm regulation were used to treat V. variegatus before waterless transportation. The optimal treatment method was screened with the survival time and survival rate as evaluation indexes. The experimental results showed that []in the process of cold acclimation, the survival rate was 83.33%, which was twice as high as that without cold acclimation, when the cooling rate was 1 ℃/h and the water was not transported for 24-36 hours. Based on cold acclimation, supplemented with 300 mg / L vitamin C and 100 mg / L anesthetic MS-222, the 24-hour survival rate increased to 100%. In addition, the survival rate was 50%, which was 200% higher than that of the total dark group, supplemented with 500 Lux light intensity and 48 hours of waterless transport. The experiment shows that cold acclimation, addition of vitamin C, anesthetics and biorhythm regulation can effectively reduce the stress response of V. variegatus during transportation, reduce fish damage, prolong the survival time, and improve the survival rate of transportation, which can meet the requirements of convenient, green and efficient commercial transportation of V. variegatus. Among them, the 500 Lux light intensity treatment method was used to transport the best survival rate of V. variegatus.

With the development of deep learning technologies, object detection has become an important task in computer vision and has been widely applied in various fields. The YOLO (You Only Look Once) series of models, known for their efficient and fast inference capabilities, have become mainstream in the field of object detection and are widely used in various domains. In the aquaculture industry, diagnosing and treating fish diseases is crucial for preventing the spread of diseases and reducing economic losses. To address the problem of bacterial disease detection in freshwater fish, this paper focuses on the application of the YOLOv8 model in object detection and explores the role of data augmentation in improving model performance. Firstly, the basic principles and architecture of YOLOv8 are introduced, and the improvements of this model over previous YOLO versions are analyzed in detail, including the advantages of its network structure and optimization algorithms. Next, this paper proposes a fish disease detection method based on an improved YOLOv8 algorithm. This method incorporates the EMA (Efficient Multi-Scale Attention) attention mechanism into the backbone network, which not only enhances the feature extraction capability but also improves multi-scale feature extraction and cross-space learning architecture. This innovation reduces computational complexity while maintaining high-precision feature representation. Additionally, the GSConv (Grouped Shifted Convolution) operation is adopted in the Neck layer to replace traditional convolution operations, which reduces model complexity and further enhances detection speed without compromising accuracy. Experimental results show that this method achieves a 2.1 percentage point improvement in detection accuracy on our self-built freshwater fish disease dataset compared to the original YOLOv8 model. It also demonstrates significant performance improvement over other existing models. This method can be applied to fish disease detection and prevention scenarios, providing technical support for fish disease detection.

The aim is to explore the best extraction technology of gelatin from black carp skin in order to improve the additional output value of black carp. Black carp is one of the four indispensable fish in traditional freshwater culture in China. It is rich in high-quality trace elements such as protein, phosphorus, selenium, iodine, iron and calcium, which are beneficial to human health. However, at present, in the processing of black carp, except fish products, black carp skin as a by-product has not been fully developed and utilized, and its potential economic value has not been fully tapped, resulting in a great waste of resources. Black carp skin is rich in collagen and is an ideal raw material for extracting gelatin. In this work, the effects of ultrasonic time, enzyme dosage, enzymolysis time and enzymolysis temperature on the extraction yield of gelatin from black carp skin were systematically studied by single factor experiment and Box-Behnken experimental design. Gelatin was extracted from black carp skin by ultrasonic treatment and enzymatic hydrolysis. The influence range and trend of each process were preliminarily determined by single factor experiment. Based on the results of single factor experiment, ultrasonic time, enzyme dosage, enzymolysis time and enzymolysis temperature were selected as key process parameters, and Box-Behnken experimental design was carried out. Through regression analysis, a regression model was established to predict the extraction yield of gelatin, and the optimum extraction conditions were determined. The results showed that the optimum extraction conditions of black carp skin gelatin were ultrasonic time 125 min, enzyme dosage 0.22%, enzymolysis time 154 min and enzymolysis temperature 45℃. Under this condition, three parallel experiments were carried out, and the average extraction yield of gelatin from black carp skin was 18.28%, and the relative error between it and the predicted value was only 0.22%, which indicated that the constructed regression model had high reliability and accuracy. In addition, the extracted gelatin was characterized by FTIR. The results showed that the extracted substances had the basic characteristics of gelatin, such as amide A band, amide I band, amide II band and amide III band, which further confirmed the gelatin properties of the extracted substances. This study provided a technical reference for the development and application of black carp skin resources in gelatin and related products. By optimizing the extraction process, the high-value utilization of black carp skin can be realized, which contributed to the sustainable development of aquatic processing industry. At the same time, it also provides reference and enlightenment for the development and utilization of other fish skin resources.

In order to solve the problem of poor stability and weighing accuracy of the load cell under ship load condition, the effect of ship swaying on the output of four-arm bridge resistive load cell was studied. The mass data of single fish at transverse tilt angle (0°~22.5°) and longitudinal tilt angle (0°~10°) were obtained, and analyzed by multivariate regression analysis on the output mass of the load cell and the tilt angle. A multi-layer BP neural network structure was constructed with the architecture of a 4-layer forward feedback [3-8-1-1] BP neural network, and the BP neural network was used to make predictions and adjust the parameters with a training model so that it could accurately predict the quality of the fish, and the algorithmic compensation method was studied. The results showed that the multiple regression coefficients estimated in the optimal linear equations reached the significant level (P<0.01) for different raw material qualities, indicating that the established linear regression equations had high reliability and good linearity, and the results of regression analysis and finite element analysis were consistent. The BP neural network model was used to construct the compensation method of shipboard instantaneous weighing data, and the actual mass value was predicted by the ship's transverse and longitudinal tilt angle, and the BP model showed good validity, high accuracy and good generalization ability for the change of weighing data under single action of transverse tilt and longitudinal tilt, as well as under the composite action, and the error rate of the BP model was reduced to 0.092% after compensation, which is very close to that of the mass value under the horizontal state, with a low error rate.The results of this research can provide a reference for the weighing of aquatic products under shipboard conditions.

In aquaculture, the accumulation of leftover feed on the water surface not only leads to wastage but also contributes to deteriorating water quality, significantly impacting the well-being and growth of aquatic organisms. Conventional detection methods face challenges in accurately identifying small feed particles due to the intricate nature of aquatic environments. To tackle this issue, this research introduces an enhanced algorithm based on YOLOv8n for detecting residual feed on water surfaces.This algorithm improves the precision of detecting small feed particles by incorporating a specialized detection layer tailored for small targets. By amalgamating shallow and deep feature information, the algorithm enhances the network's ability to perceive targets across various scales, thereby boosting the accuracy of detecting small feed particles. Furthermore, the integration of the C2f_Faster_EMA module reduces model parameters, elevates detection speed, and fortifies the extraction of intricate features. Additionally, the devised ICBAM module bolsters the amalgamation of feature information for small targets, significantly enhancing detection accuracy.Experimental findings illustrate that the enhanced algorithm delivers exceptional performance across multiple evaluation metrics. Comparative to the original YOLOv8n, the @0.5, precision, and recall rates have surged by 10.3%, 7.6%, and 10.2%, respectively. Furthermore, the algorithm achieves a detection speed of 125 frames per second FPS, meeting the demands for real-time detection. These outcomes underscore the algorithm's capacity to swiftly and accurately identify residual feed on water surfaces, providing substantial technical backing for the intelligent administration of aquaculture.The implementation of this algorithm holds promise in efficiently curbing feed wastage, enhancing water quality, and amplifying the profitability of aquaculture operations. This advancement positions the aquaculture sector on a trajectory towards a more sustainable and efficient future.

Targeting the issues of high labor intensity, uneven feed distribution, and low efficiency in aquaculture feeding, a ground - rail - based rail - type precision feeding system was designed. This system integrates mechanical design, automatic control, and upper - computer monitoring with feeding management. Key components like the traveling, silo, feeding, and weighing devices were designed and analyzed to determine structural parameters. An automatic control system using SIEMENS S7-200 SMART PLC was developed, and tests on driving speed, positioning accuracy, feeding speed, feeding accuracy, and feed crushing rate were conducted. Results show the system runs stably, starts/stops automatically, moves at 12.7 m/min, has a positioning accuracy error of 39 - 58 mm, feeds at 3.31 kg/min, with a feeding accuracy error < 0.63% and a feed crushing rate < 1%. The entire feeding process is automated, with real - time monitoring by the upper computer. This system boosts feed utilization and cuts labor and feeding costs. Its integrated design improves management and offers a viable solution for aquaculture automation.

Rainbow trout (Oncorhynchus mykiss) is known for its tender, delicious, and nutritious flesh. To preserve its freshness, choosing an appropriate thawing method is crucial for maintaining fish meat quality. This study aims to identify the optimal thawing method to enhance the quality of thawed rainbow trout. To comprehensively investigate the effects of different thawing methods (hydrostatic thawing, flowing water thawing and microwave thawing) on the quality of rainbow trout, so as to screen out the most suitable thawing methods to improve the quality of thawed rainbow trout. This study employed a series of detection methods to systematically measure thawing curves, water-holding capacity, color changes, texture properties, malondialdehyde content, K value, microscopic structural characteristics, and sensory evaluation. A comprehensive comparative analysis was conducted on the quality differences of rainbow trout under different thawing methods. While hydrostatic thawing and flowing water thawing are simple to operate, they are time-consuming, taking 13.2 min and 10.5 min, respectively. Moreover, the water-holding capacity and texture properties of the fish after thawing were poor, affecting the final quality of the fish. Microwave thawing was the fastest, requiring only 4.2 min, but it had a significant drawback: the fish exhibited higher lipid oxidation, with a K value of 51.87%, significantly higher than that of other thawing methods (P<0.05), indicating a substantial impact on fish freshness. In contrast, ultrasonic thawing not only took less time (5.7 min) but also excelled in maintaining the water-holding capacity and texture properties of the fish. The thawed fish had a bright orange color, intact muscle fibers, clear microscopic structure, and effectively slowed the process of lipid oxidation, demonstrating unique advantages in preserving fish quality. Ultrasonic thawing not only meets consumers' expectations for the appearance quality of food but also aligns with the market's demand for high-quality ingredients, showing good market acceptance and potential commercial value. Therefore, ultrasonic thawing is more suitable for large-scale industrial thawing operations, as it can significantly improve thawing efficiency while better maintaining the freshness and taste of rainbow trout post-thawing. These findings provide a strong theoretical basis and practical guidance for enhancing rainbow trout product quality and processing efficiency, reducing thawing time and energy consumption, meeting the demand for high-quality aquatic products, and promoting related industry development.

This study aims to scientifically assess the disaster risks of ship net-type cages in wave environments, address the challenges in disaster prevention and control under extreme wave conditions, and promote the development of the offshore aquaculture industry. Numerical simulations were conducted using the AQWA hydrodynamic module in ANSYS to simulate the dynamic processes of ship-type net cages under various structural and wave conditions. After obtaining the data, a neural network algorithm was employed to construct the nonlinear relationship between disaster factors and structural damage, while the grey relational analysis method was used to identify the dominant disaster-causing factors. The results show that the structural motion responses and dynamic loads calculated by the numerical model closely match the test results, with an error of no more than 10%. The established neural network model accurately predicts the dynamic disaster situations, with a prediction error of no more than 5% and a root mean square error of no more than 0.52. It was determined that wave height is the dominant factor for mooring line breakage, and the floating frame length and wave height are the dominant factors for floating frame cracking. The research demonstrates that the neural network model can effectively predict the disaster damage for ship-type net cages and provides significant support for mooring line selection and floating frame safety assessment.

Compared with the open space of the aquaculture cage, the space of the aquaculture ship is closed and narrow, which is difficult to accommodate the huge suction pump operation equipment. At present, the centrifugal suction pump has the advantages of compact structure, flexible installation and not out of water during the whole fishing process compared with the vacuum type and jet flow, which is especially suitable for the aquaculture ship. To address the challenge of minimizing fish damage and enhancing the efficiency of fish collection in aquaculture ship, a low-damage fish suction pump with a diameter of 200 mm has been developed. The computational fluid dynamics-discrete element method (CFD-DEM) is used to analyze the flow field characteristics of the impeller and optimize the performance of the suction pump. Flow line distribution is uniform, no fish body extrusion and blockage; at the same time, the pressure distribution in the pump channel is uniform, and it will not cause too much damage to the fish. Fish suction pump test, at the outlet end with a net bag to separate the fish water, the results show that only a small number of shark sucker has slight scratches, suspected to be scratched by a mesh bag during the separation, and no trace of impeller scratches, meet the non-destructive live fish transport requirements. The results show demonstrates that fish suction pumps can be adapted to accommodate various fish species by adjusting the pump's diameter and rotational speed. This customization minimizes fish injury, reduces the physical labor required, and enhances both the efficiency of fish harvesting and the survival rate of the caught fish.

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.

Squid is a significant aquatic product in China, yet its processing industry remains labor-intensive, leading to low efficiency and high labor intensity. This study introduces an image recognition-based soft-body modeling method to generate a 3D model of a suspended and inflated squid mantle from 2D images, providing a foundation for automated squid processing. The method uses OpenCV for image recognition to extract edge contours and geometric features of the squid mantle. MATLAB then refines these contours, deduces inner cavity contour points, and determines the mantle's rotational state. The contours are rotated around the central axis to construct a mesh model. This process accurately captures the shape of the squid mantle during processing, accounting for its deformable and flexible nature. Validation was performed using two datasets: different postures of the same squid body and five squid bodies of varying sizes. Results show that the maximum error in the model’s outer contour length compared to the actual body size is 0.66%, and geometric size errors across three postures are within 1%. This confirms the method's accuracy in generating 3D models from 2D images of squid bodies in various poses. The method ensures precise contour representation and is suitable for automated path planning in tasks like cleaning and cutting. Its non-contact nature makes it ideal for food processing, avoiding radiation issues associated with CT scanning. This study lays a foundation for automated squid processing, supporting tasks such as cleaning, cutting, and grading.

As a new type of fishery cultivation equipment, the deep - sea aquaculture cage can cultivate fish with high economic value in the sea areas far away from the land. In order to explore the possible damage that the instability of the net - hanging poles may cause to the main structure of the platform, this paper takes a certain aquaculture platform in Guangdong as an example. Using finite - element software, displacements in different directions sufficient to cause fracture in the poles are applied to the free ends of the net - hanging poles. These displacements are designed to study the cracking process and ultimate bearing capacity of the typical nodes when they are subjected to forces in different directions. Different - thickness outer plates of the floating boxes are also set up to study the influence of the relative stiffness between the outer plates and the net - hanging poles on the fracture behavior and ultimate bearing capacity of the typical nodes. Through numerical calculations, it is found that when the same load is applied to the typical nodes with different plate thicknesses, the main structures of the 6 - mm and 8 - mm outer plates crack first, while for the 10 mm and 12 mm outer plates, the net - hanging poles fracture before the main structures. The results show that when the relative stiffness increases from 0.5 to 0.67, the weight increases by 8.8%, and the deformation - resistance capacity increases by 44%; when the relative stiffness increases from 0.67 to 0.83, the weight increases by 8.1%, and the deformation - resistance capacity increases by 33%; when the relative stiffness increases from 0.67 to 1, the weight increases by 7.5%, and the deformation - resistance capacity increases by 25%. It can be considered that the increase in the steel material of the typical nodes has little effect on the improvement of the ultimate bearing capacity, and an appropriate reduction in the plate thickness can be considered in the platform design stage. The analysis results show that if the stiffness of the main structure of the aquaculture cage is much greater than that of the poles, the fracture phenomenon is usually limited to the welds and the roots of the net - hanging poles and cannot extend to the main body of the aquaculture cage, resulting in only local plastic deformation of the main structure. On the contrary, when the stiffness of the main body of the aquaculture cage is lower than or close to that of the poles, the main structure of the node fractures first, and the fracture area gradually expands to the pole part. The results also show that the ultimate bearing capacity of the typical nodes of the net - hanging poles increases significantly with the increase in the thickness of the outer plates of the floating boxes. Based on this discovery, this paper proposes the calculation equations for the ultimate bearing capacity of the typical nodes in various directions, providing a theoretical basis for relevant engineering designs. 

To explore the gas - liquid - solid three - phase flow characteristics during the operation of the pneumatic lift sludge suction equipment in the hatchery tank and establish a structural optimization method for the pipeline gas lift sludge suction device, the Fluent computational fluid dynamics tool was used. Based on the Euler multi - phase flow model and the dense discrete phase (DDPM) model, the influence of the structural form of the pneumatic lift pool bottom sludge suction equipment on the sludge suction performance was analyzed. The test results show that: the gas - liquid - solid three - phase flow process within the air - lift pipeline can be divided into the initial stage, pressure relief stage, lifting stage, and stable stage. The diameter, number, and spacing of the openings in the air - lift pipeline, as well as the height from the bottom, directly affect its sludge suction performance. Appropriate adjustment of the opening spacing can enhance the effectiveness of sludge suction. The optimal diameter for the openings in the air - lift pipeline is approximately 4 mm. Increasing the number of openings in the air - lift pipeline by 2.5 times results in a 27.2% decrease in the efficiency of the air - lift system. In contrast, increasing the height of the pipeline from the bottom by 3 times leads to a 31.6% reduction in system efficiency. Therefore, it is advisable to avoid increasing the number of openings and the height from the bottom in the air - lift pipeline.

 In order to explore the suitable light conditions of Apostichopus japonicus in indoor culture, 1680 juvenile sea cucumber (weight 0.185±0.014 g) were placed in three irradiance (1 000 mW/m2, 2 500 mW/m2, 4 000 mW/m2) in the environment of red (R)、full spectrum (W) and dark (D) for 35 days. The results showed that different spectra and irradiance could significantly affect the growth and physiological function of juvenile sea cucumber. The body weight of the red light 4 000 mW/m2 group was significantly higher than that of the full spectrum 4000 mW/m2 group (P<0.05). The body length of the red light 1 000 mW/m2 group was significantly higher than that of the full spectrum 4000 mW/m2 group(P<0.05). The specific body weight growth rate of the red light 1000 mW/m2 group was significantly higher than that of the full spectrum 4000 mW/m2 group (P<0.05). The survival rate of the red light 4000 mW/m2 group was significantly higher than that of the full spectrum 4000 mW/m2 group(P<0.05). For enzyme activity, amylase (AMS) activity was the highest in the red light 4000 mW/m2 group and lipase (LPS) activity in the red light 2500 mW/m2 group. The activities of acid phosphatase (ACP) and alkaline phosphatase (AKP) in the red light 4000 mW/m2 group were significantly higher than those in the red light 1000 mW/m2 group (P<0.05). The catalase (CAT) activity was the highest in the full spectrum 2500 mW/m2 group. The activity of superoxide dismutase (SOD) was the highest in the red light 4000 mW/m2 group, which was significantly higher than that in the full spectrum 1000 mW/m2 group(P<0.05). In summary, it is recommended to use red light to cultivate juvenile ginseng in an indoor culture environment and control the irradiance at 1000-4000 mW/m2. In this study, the effects of three irradiance degrees on the juvenile ginseng were studied, and the results showed that the growth performance of the juvenile ginseng with red light of 1000-4000 mW/m2 was better. In order to accurately and optimally determine the most appropriate irradiance, a fine irradiance gradient was recommended to further evaluate the effect of irradiance on the young radiance.

To explore the effects of different wall conditions on fish swimming ability, crucian carp, a typical fish with carangiform swimming mode, was selected for 1:1 biomimetic modeling. Computational fluid dynamics (CFD) combined with dynamic meshing technology was employed for 2D unsteady simulations of autonomous propulsion under various wall conditions. The study analyzed the impact of kinematic parameters like frequency (f) and amplitude (A) on swimming performance across different wall scenarios. Results showed that at low frequency (f=1.7 Hz) and small amplitude (A=0.04 L), a single - sided wall increased the fish's acceleration during the start - up phase and its cruising speed. When frequency rose from 1.7 Hz to 2.5 Hz at constant amplitude, acceleration under single - and double - sided walls rose by 52.7% and 75.9%, respectively. Similarly, when amplitude increased from 0.06 L to 0.07 L at constant frequency, acceleration under single - and double - sided walls rose by 32.4% and 33.3%, respectively. In low - frequency and small - amplitude conditions, a single - sided wall significantly enhanced propulsion. Within the low - frequency and high - amplitude range, increasing frequency and amplitude can significantly improve swimming speed. This study offers a useful reference for fish behavior research.

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.

Portunus trituberculatus has high nutritional and economic value, and its appearance integrity directly affects its market value. At present, the sorting of Portunus trituberculatus faces challenges due to low levels of automation in traditional methods. Traditional sorting of Portunus trituberculatus is generally done manually, which has the problems of low efficiency and high labor costs, and human observation is easily affected by subjective factors. To solve the sorting problem of Portunus trituberculatus, this paper proposes a defect recognition model for crabs based on an improved ConvNext model , which can accurately identify the feet of Portunus trituberculatus and carry out intelligent recognition and grading. By accurately identifying the feet of Portunus trituberculatus, intelligent recognition and grading are carried out. Using re-parameterized refocusing convolution to replace depthwise separable convolution in the ConvNext model block, the network is able to capture richer and more detailed features. Coordinate attention mechanisms are added before the Block module and after the Downsample module of the ConvNext model to enhance the model's attention to key features and discard irrelevant features. The results show that the improved model has the highest accuracy on the validation set, at 98.90%, which is 3.32% higher than the original ConvNext baseline model network. The proposed algorithm ensures effectiveness. This study contributes to achieving the goal of intelligent and precise grading in the Portunus trituberculatus industry, and is anticipated to replace traditional methods to improve the sorting efficiency of Portunus trituberculatus. This can provide technical support for the further development of an automatic recognition and classification system for defects in Portunus trituberculatus.

This study aimed to evaluate the feasibility of Biofloc technology (BFT) in Carassius auratusvar. Pengze aquaculture and to investigate the effects of total suspended solids (TSS) concentration on the growth of Pengze crucian carp, its intestinal tract, and the microbial community structure in the aquaculture water. The experiment included four TSS concentration groups: BF300, BF500, BF700, and BF900, as well as a water-exchanged control group (CW), and the Pengze crucian carp were cultured for 120 days. The results showed that the total ammonia nitrogen and nitrite nitrogen in the water of the Biofloc treatment groups could be maintained at low levels. The highest weight gain rate, body condition, specific growth rate, and condition factor were observed in the BF500 group, which also had the lowest feed coefficient of 1.42. In addition, there was no significant difference in the content of T-SOD and LSZ among the groups (P > 0.05). Microbiome analysis showed that the richness index of the intestinal microbial community in the Biofloc group decreased with the increase of TSS concentration in Pengze crucian carp; the dominant bacterial phylum in the intestine was Proteobacteria, Bacteroidota, Fusobacteriota, and Actinobacteriota, with Proteobacteria being the main bacterial group. The dominant bacterial phylum in the aquaculture water of the Biofloc group was Proteobacteria, Bacteroidota, Chloroflexi, and Actinobacteriota. In summary, the optimal TSS concentration for Pengze crucian carp was 500 mg/L, and BFT can serve as a new model for the green aquaculture of Pengze crucian carp.

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 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.

To investigate the water quality variations and microbial community structure in the aquaculture zone of a freshwater pond with an embedded container recirculation aquaculture system, this study measured water quality indicators in the zone containing a three - stage biofilter (sedimentation tank, oxidation tank, purification tank, and filter dam) and biofill (filter cotton and brush). High - throughput sequencing was also employed to analyze the microbial community structure in the water column of each biofilter and on the biofill. Results indicate that the water purification system in the aquaculture zone operates stably and effectively, with the treated water quality meeting aquaculture requirements. The removal rates of ammonia nitrogen (NH4+-N), nitrite nitrogen (NO2--N), and total nitrogen (TN) were 52.97%, 63.23%, and 53.51%, respectively. The bacterial community in the aquaculture zone consisted mainly of 33 phyla, including Proteobacteria, Actinobacteria, and Bacteroidota. In the biofilter, the bacterial community structure of the biofilm differed from that of the water column, with a significantly higher relative abundance of Actinobacteria on the biofilm (P < 0.05). The water column samples had higher bacterial community diversity and richness than the biofilm samples. Correlation analysis revealed that NH4+-N, NO2--N, and TN significantly influenced the microbial community structure in the water column group (P < 0.05), while TP, AP, and DO had a more significant impact on the bacterial community structure in the biofilm group. In conclusion, the three - stage biofilter can effectively increase the microbial flora that promotes nitrogen and phosphorus metabolism, contributing to stable water quality. These findings provide theoretical support for the construction and water quality regulation of freshwater pond embedded container recirculation aquaculture systems.

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.

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.

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. 

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.

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.

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.