As a critical tool for modern fishery resource monitoring and assessment, imaging sonar has demonstrated significant potential in fishery resource surveys, fish behavior analysis, and habitat protection. Despite challenges such as environmental complexity, resolution limitations, and large-scale data processing, this technology continues to advance. This paper systematically reviews the progress of imaging sonar technology in fisheries, thoroughly analyzes existing challenges, and envisions future developments. It focuses on multiple application scenarios, including complex and sensitive habitat monitoring, target detection in low-visibility environments, fish behavior analysis, and species population estimation. The paper also comprehensively examines the domestic and international research status of imaging sonar applications in fisheries. Based on this review, it explores future directions for imaging sonar development from several dimensions, such as enhancing resolution, developing automated data processing methods, achieving miniaturization and lightweight design, and promoting integrated design. These advancements aim to facilitate the widespread application of imaging sonar in fisheries and support scientific management and decision-making for fishery resources.

Oysters hold the top position in terms of production among shellfish farming species, demonstrating significant economic value. However, current farming facilities face challenges such as low levels of standardization and mechanization, as well as fragility to wind and waves. These issues severely limit the sustainable development of the oyster farming industry. In this research, an elevating oyster farming platform was meticulously designed. Subsequently, the physical model test method was employed to comprehensively investigate the hydrodynamic characteristics of the platform under various wave parameters, drafts, and mooring configurations. The research indicates that the motion responses and mooring line forces of the farming platform are positively correlated with wave height and period. In contrast, the growth rates of the motion responses and mooring line forces are negatively correlated with the period. Under identical working conditions, the amplitude of heave and pitch motion changes more dramatically. Under extreme sea conditions, when the farming platform transitions from the floating state to the submerged state, the surge, heave, pitch, and mooring line forces are reduced by 27.32%, 45.89%, 42.32%, and 18.47%, respectively. This transition significantly enhances the platform's capacity of withstanding wind and waves. Notably, the attenuation effects on the heave and pitch motions are the most pronounced. The motion responses and mooring line forces of the slack mooring farming platform are relatively lower than those under the tension mooring condition. Moreover, their increase exhibits an approximately linear relationship. This research not only provides a theoretical support for the development of oyster farming platforms but also offers a critical reference value for the design and research of other shellfish farming platforms.

To accurately predict the air gap performance of offshore frame-type aquaculture platform, a frame-type aquaculture platform was selected as the research object. Based on linear wave diffraction/radiation theory, Morrison equation theory, and rigid body kinematics principles, frequency-domain method was employed to analyze air gap performance. The effects of viscous loads on structural slender members and nettings, disturbed wave surface elevation, position mooring system stiffness on air gap performance were analyzed. Key findings from comparative analysis include: viscous loads on structural slender members and nettings substantially improve platform motions and optimize air gap performance, with a decrease range of about 0.3-1.0 m; Disturbed wave surface elevation significantly affects the air gap performance of frame-type platforms, with an increase range of about 0.2-0.7 m and a decrease range of about 0.3-1.6 m; Position mooring system stiffness constrains platform motion and affects the air gap results, with a decrease range of about 0.1-0.4 m. The results emphasize that the effects of viscous loads on structural slender members and nettings, disturbed wave surface elevation, position mooring system stiffness should be considered reasonably in frame-type aquaculture platform air gap analysis.

To address the defects of traditional vertical flow sedimentators, such as low particle interception efficiency under high hydraulic loads and vulnerability to turbulent interference, this study designed a vortex-type vertical flow sedimentation filter. By integrating the principles of vertical flow sedimentation and cyclone separation, and combining CFD-DPM coupled simulation with experimental verification, the study systematically explored its enhanced removal mechanism for suspended particulates in recirculating aquaculture systems (RAS). Numerical simulations showed that the vortex structure optimizes the flow field distribution through the synergistic effect of centrifugal force and gravity, effectively suppressing particle escape. In comparative tests, under a hydraulic load of 15 m³/(m²·h), the vortex-type filter achieved interception rates of 72.92%±7.40% and 59.24%±5.15% for influent total suspended solids (TSS) concentrations of 25 mg/L and 50 mg/L, respectively, representing improvements of 28.6% and 36.0% compared to traditional devices (P<0.05). However, there was no significant difference in the variation of effluent TSS concentration with increasing flow rate between the two devices (P>0.05). The study demonstrates that the vortex design shortens the hydraulic retention time through a cyclone-enhanced mechanism, significantly improving the stability of particle interception under high-load conditions and addressing the performance degradation of traditional devices caused by increased flow velocity. This achievement provides a solution combining high efficiency and engineering applicability for optimizing solid-liquid separation equipment in RAS.   

In order to solve the problems of large amount of water drainage, deterioration of water quality in the late stage of eel culture, and high investment and operation cost of equipment and facilities, this study optimized a water-saving and emission-reducing aquaculture process for eel and applied it in practical scenarios. An orthogonal experimental design was employed to develop an in-situ water treatment technology using "bacterial granules-composite bacterial liquid agents" based on three selected functional strains with nitrogen and phosphorus removal capabilities. The optimized industrialized water-saving and emission-reducing aquaculture process was then demonstrated through controlled experiments at different stocking densities for fingerling eel over a 120-day culture period. The results showed that in Treatment Group I (500 ind./m³), the harvest size, yield, specific growth rate, and absolute weight gain rate of the fry were significantly higher than those of the control group by 41.4%, 43.9%, 17.3%, and 48.2%, respectively (P<0.05), while the feed conversion ratio was significantly lower by 17.6%(P<0.01). In Treatment Group II (750 ind./m³), the harvest size, yield, specific growth rate, and absolute weight gain rate were significantly higher than the control group by 20.5%, 83.0%, 8.9%, and 23.3%, respectively (P<0.05), with the feed conversion ratio significantly lower by 11.0%(P<0.01). Both treatment groups achieved over 75% water savings and emission reductions compared to the control. In Treatment Group I, the average concentrations of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, and total phosphorus in the water were significantly lower than those in the control group by 90.8%, 80.7%, 10.0%, 51.5%, and 38.7%, respectively(P<0.05). In Treatment Group II, these concentrations were significantly lower by 88.0%, 74.2%, 5.6%, 42.6%, and 21.3%, respectively(P<0.05). These findings indicate that this aquaculture process offers advantages such as water conservation, emission reduction, sustained high water quality, and low investment and operational costs, suggesting broad application prospects.

With the increasing reliance of the aquaculture industry on groundwater resources, the water quality issues caused by excessive iron and manganese concentrations in groundwater have become progressively prominent. Elevated levels of iron and manganese adversely affect the respiration, immune function, growth, and development of aquaculture organisms, thereby restricting the widespread application of groundwater in aquaculture practices. In this study, quartz sand and zeolite were chemically modified using potassium permanganate (KMnO₄) and manganese sulfate (MnSO₄) solutions, while physical modification of zeolite was achieved through high-temperature calcination. Comprehensive characterization of the modified materials was conducted. Iron and manganese filtration experiments were performed to investigate the maturation period required for achieving stable iron-manganese removal efficiency in both modified and unmodified quartz sand and zeolite. The results demonstrated that chemical modification induced the formation of spherical particles on quartz sand surfaces and created dense etching grooves on zeolite, whereas physical modification disrupted the layered structure of calcined zeolite. Energy-dispersive X-ray spectroscopy revealed Mn element proportions of 18.32% and 24.82% on chemically modified quartz sand and zeolite surfaces, respectively, primarily existing as MnO₂. Maximum specific surface areas (7.26 m²/g and 28.57 m²/g) and pore volumes (0.0052 cm³/g and 0.112 cm³/g) were attained for chemically modified quartz sand and 300℃-calcined zeolite. The 400℃-calcined zeolite exhibited peak specific surface area (20.18 m²/g) and pore volume (0.0857 cm³/g). Chemically modified zeolite demonstrated the shortest maturation period for iron and manganese removal, requiring only 10 and 8 days respectively, significantly shorter than unmodified materials. This research provides theoretical foundations and technical references for developing iron-manganese removal technologies in groundwater applications for aquaculture.

n order to survive in nature, organisms must adapt to the important environmental changes of the photoperiod, namely the day night light cycle. This study aims to investigate the response of juvenile Sebastes schlegelii to different photoperiods, five different photoperiod conditions (24 L: 0 D, 16 L: 8 D, 12 L: 12 D, 8 L: 16 D, 0 L: 24 D) were set up to observe the changes in behavior, growth, and physiology of Sebastes schlegelii under different conditions. It was found that under the 8 L:16 D photoperiod condition, the distance between individuals of the Sebastes schlegelii was relatively stable, and the group arrangement was more orderly, while under the 24 L: 0 D and 0 L: 24 D photoperiod conditions, the cohesion and coordination of the Sebastes schlegelii decreased; At the end of the experiment, the body length and weight under 8 L:16 D photoperiod conditions were significantly higher than those under other photoperiod conditions (P<0.05), and the feeding situation was good; Under 24 L:0 D photoperiod conditions, the cortisol concentration and glucose content in the plasma of Sebastes schlegelii were higher than under other experimental groups. Under 16 L: 8 D photoperiod conditions, the activities of aspartate aminotransferase and alanine aminotransferase in the plasma of Sebastes schlegelii showed an increasing trend. The results showed that under the 8 L: 16 D photoperiod conditions, the cohesion and coordination of the fish population were enhanced, making the Sebastes schlegelii more inclined to move in clusters, and also beneficial for its growth and feeding. However, under the 24 L: 0 D and 0 L: 24 D photoperiod conditions, the behavior of the Sebastes schlegelii population was poor, and the 24 L: 0 D and 16 L: 8 D photoperiod conditions were not conducive to the physiological metabolism of the Sebastes schlegelii. In summary, the results of this study aim to provide a reference for optimizing the light environment for the cultivation of Sebastes schlegelii.

 To address the issues of low intelligence, high energy consumption, high feed breakage rate, and low feeding efficiency in pneumatic feeding systems for In-pond Raceway System(IPRS), this study optimizes a single-pipe multi-channel pneumatic feeding control system using a Computational Fluid Dynamics-Engineering Discrete Element Method(CFD-EDEM) coupling simulation approach. First, the IPRS and the single-pipe multi-channel pneumatic feeding system were analyzed to identify performance optimization requirements. Second, experiments were conducted to measure the physical parameters of commonly used expanded feed, and a discrete element model of the feed was developed. Subsequently, a physical model of the feeding pipeline and a computational fluid dynamics model were constructed to simulate the motion characteristics and distribution patterns of feed particles under varying airflow velocities, enabling the selection of an optimal intelligent control strategy for airflow-feeding coordination. Results indicated that airflow velocity significantly influenced feeding efficiency and pipeline blockage risks. Under experimental conditions, an optimal airflow velocity range of 30-40 m/s was identified. By implementing frequency conversion control of the fan (36-48 Hz), airflow-feeding coordination was optimized, and pressure feedback was used to achieve residual material purging and anti-blockage control in pipelines. Compared to traditional systems, the optimized system achieved 18.6% energy savings, 39.44% reduction in feed breakage rate, and 43.48% improvement in feeding uniformity, thereby enhancing overall feeding efficiency. The CFD-EDEM method effectively simulated the operational conditions of the feeding system and provided optimization strategies. The proposed intelligent control strategy proposed in this study provides a theoretical reference for precise long-distance multi-point feeding, effectively enhancing the system’s intelligence level and operational stability, while offering valuable insights for the research and development of intensive aquaculture equipment.

 Genetically Improved Farmed Tilapia (GIFT tilapia, Oreochromis niloticus), a selectively bred strain of Oreochromis niloticus is a globally important aquaculture species known for its rapid growth and stress resistance. As a tropical fish species, GIFT tilapia is extremely sensitive to low temperatures. The overwintering period has become a major challenge for its aquaculture in most regions of China. To improve overwintering survival rates and ensure sustainable aquaculture, closed aquaculture systems have gained increasing attention. Closed aquaculture systems mainly include recirculating aquaculture systems (RAS) and biofloc technology (BFT). They offer significant advantages in water conservation, temperature control, and environmental sustainability. However, the microbial community dynamics and ecological interactions in RAS and BFT systems under overwintering conditions remain unclear. This study investigated the structural evolution of microbial communities in water and fish tissues under RAS and BFT systems during overwintering. High-throughput 16S rDNA sequencing was employed to characterize these communities. In this study, two treatment groups were established: RAS groups and BFT groups. Each group included three replicates. Both groups were stocked with juvenile GIFT tilapia. They were maintained under identical stocking densities and environmental management. At the beginning and end of the culture period, samples were collected from the water, biofilter media (RAS groups), biofloc particles (BFT groups), as well as from the intestinal and gill tissues of the fish. These samples were used for microbial DNA extraction and subsequent diversity analysis. In addition, key water quality parameters, including ammonia nitrogen, nitrite, and nitrate were monitored to evaluate environmental changes during the culture process. Alpha diversity analysis revealed that the Chao1 and Simpson indices of RAS water, biofilter media, and BFT water samples increased during the overwintering period. In contrast, the microbial diversity in the intestinal and gill tissues of the fish showed a decreasing trend. At the early stage of culture, Proteobacteria (75%) dominated the microbial community in the RAS groups, with Paracoccus (34%) being the predominant genus. Meanwhile, the BFT groups was mainly composed of Firmicutes (86%) and Bacillus (85%). By the end of the culture period, the proportion of Proteobacteria in the RAS system had decreased to 26%. Chloroflexi (43%) became dominant in the BFT groups, and the relative abundance of Bacillus dropped to 3%. The dominant phyla in the biofilter shifted from Proteobacteria in the early stage to Chloroflexi and Actinobacteria later on. Notably, at the end of the culture period, the microbial composition of the water and GIFT tilapia intestines in the BFT groups showed strong consistency. They shared dominant phyla including Fusobacteria, Proteobacteria, Chloroflexi, and Bacteroidota. In contrast, the microbial correlation between the water and fish intestines in the RAS groups was relatively weak. In summary, different overwintering aquaculture models significantly altered the microbial communities in the rearing water and the intestinal tract of GIFT tilapia. This study provides some theoretical foundation for the development of low-temperature overwintering strategies for GIFT tilapia, and offers practical guidance for the optimization and application of RAS and BFT systems. For overwintering aquaculture, it is recommended to choose the BFT systems as the preferred model for GIFT tilapia.

 Dissolved oxygen, a crucial water quality factor in aquaculture, requires precise control. This study proposes a Modified Smith fuzzy PID controller to tackle the control challenges posed by the time-varying, nonlinear, and time-delay characteristics of dissolved oxygen control systems. By incorporating a fuzzy PID algorithm into a Modified Smith predictor, this approach aims to mitigate the impact of model mismatch on dissolved oxygen control. Simulations were conducted under both matched and mismatched theoretical and actual model conditions. Results indicate that compared to conventional PID, fuzzy PID, and Smith fuzzy PID controllers, the Modified Smith fuzzy PID controller exhibits significantly lower maximum overshoot (0.78% on average) and achieves target dissolved oxygen concentrations in the shortest time (approximately 371 seconds). Experimental validation in real dissolved oxygen control processes further confirms its superiority. The Modified Smith fuzzy PID controller demonstrates the best control performance, with accuracy and robustness meeting the requirements for precise dissolved oxygen control in recirculating aquaculture systems.

Underwater biological target detection still predominantly relies on manual identification methods, facing challenges related to low levels of intelligence. Existing target detection algorithms, such as the YOLO series, suffer from issues such as large parameter counts, high computational requirements, and poor detection accuracy. This paper proposes an improved algorithm based on the RT-DETR model. The DynaShareNet backbone network is introduced, which shares stem information architecture to enhance feature fusion efficiency and reduce computational burden; the Dilated Transformer Attention Block (DTAB) is introduced to combine global and local feature interactions to enhance robustness in complex underwater environments; the MaSA-RetBlock module is adopted to address target blurring and low-contrast recognition issues; and the EMASlideVarifocalLoss is introduced to enhance the ability to handle difficult-to-classify targets. Experimental results on the URPC2020 dataset demonstrate that the improved algorithm significantly enhances detection accuracy, with mAP50 and mAP50:95 improving by 3.3% and 3.5%, respectively, while significantly reducing model complexity, with parameter counts and computational costs decreasing by 41.7% and 47.7%, respectively. The detection accuracy and parameter count/computational complexity outperform YOLO series algorithms, and the algorithm demonstrates excellent generalization performance on the RUOD dataset. The study indicates that the improved algorithm effectively enhances the performance and efficiency of underwater target detection, offering promising application prospects.

To study the heave motion of multi-fishing vessels anchored side-by-side with bow and stern anchors, and to analyze the relationship between their maximum downward heave and wave height.  A physical model test was employed to study the heave motion of single, double, triple, and quadruple fishing vessels anchored together. The research focused on analyzing the impacts of wave period, wave incidence direction, the number of anchored vessels, and vessel position on the heave motion under both pure wave action and combined wind and wave action. The results show that, for single-vessel anchoring, the maximum downward heave is approximately 0.5 to 0.8 times the wave height for wave directions of 90° and 45°, and approximately 0.25 to 0.65 times the wave height for a wave direction of 0°. When two vessels are anchored together under the action of pure 90° waves, the maximum downward heave is approximately 0.3 to 1.1 times the wave height. For three or four vessels anchored, it is approximately 0.5 to 1.2 times the wave height. Under combined wind and wave action, the maximum downward heave of a single vessel is about 0.4 to 0.6 times the wave height, 0.6 to 0.8 times for two vessels, and 0.8 to 1.2 times for three or four vessels. The research findings provide a reference for ensuring the safe and stable anchoring of fishing vessels within harbors.

 Squid industry is an important part of my country's marine economy, but the squid processing industry is limited by manual labor, which seriously restricts the upgrading of the industry. In order to realize the automation of the separation process of squid carcass, viscera, fins and heads, this study designed a carrier with a "fin-clamping and neck-hanging" fixed mode for squid according to the structural characteristics of squid, and designed a squid automatic feeding module, squid yellowing, yellowing, finning and head removal structure by analyzing the characteristics of manual labor. The automatic feeding module realizes squid posture recognition based on the Faster-RCNN neural network model, realizes squid grabbing point solution based on the fast DT algorithm, and uses collaborative arms to complete the automatic feeding of squid; the yellowing, yellowing, finning and head removal structure fusion control program realizes human-like operation. The test results in the squid processing plant show that the fully automatic removal equipment for squid by-products can realize the automatic feeding, visceral removal, finning and head removal of squids in the specification range of 100-400g, with a processing efficiency of 45 pieces/minute, and a single device can save 3 people. Research has shown that the fully automatic squid by-product removal equipment can simulate humans to complete the work of removing squid viscera, fins and heads, achieving the same operating effect, reducing labor intensity while improving work efficiency. Its promotion and application can improve the intelligence level of the squid processing industry.