International Journal of Marine Science, 2025, Vol.15, No.6, 303-312 http://www.aquapublisher.com/index.php/ijms 306 3.3 Aeration systems, recirculating aquaculture systems (RAS), and facility improvements In actual production, many problems in aquaculture are often not due to any major issues with the fish and shrimp themselves, but rather because the facilities are not up to standard and the environment is difficult to stabilize. Oxygenation equipment is a typical example. Conventional devices such as waterwheel aerators and microporous aeration pipes are not installed to "improve technical levels", but because local hypoxia is very likely to occur in water bodies, especially when water layers differentiate (Jamil and Latip, 2023). Once the dissolved oxygen drops below the critical point, the machine must be turned on immediately; otherwise, the stress response of fish and shrimp will come very quickly, and in severe cases, they may even die. In fields with higher density, sometimes a pure oxygen system is also needed to support the oxygen consumption. The idea of the circulating water system (RAS) is completely different. It is more like confining the water body in a controllable space. The system continuously purifies water through mechanical filtration, biological filters, ultraviolet disinfection and other processes, and then recycles it back into the pool for reuse. In this way, the frequency of water replacement can be reduced, and it is more difficult for external pathogens to enter. Many highvalue varieties achieve stable year-round breeding precisely through this approach. As for the renovation of traditional facilities, they often seem insignificant, but the effect is very practical. For instance, laying anti-seepage membranes or installing bottom drains in ponds can help reduce the accumulation of harmful sediment. Indoor constant-temperature workshops and automatic feeding systems can reduce the interference caused by weather and human operation (Liao et al., 2025); After upgrading the structure of the offshore cages, both the water exchange rate and the ability to resist wind and waves will be better. Through these adjustments, the environment is more likely to remain within an acceptable range for animals, and thus they are less likely to develop diseases due to environmental stress. 4 Disease Early Warning and Diagnostic Techniques 4.1 Application of PCR, LAMP, and metagenomic sequencing in pathogen identification In the early diagnosis of aquatic diseases, molecular detection has almost become a routine method, but the specific application varies depending on the scenario. For example, PCR is highly sensitive and targeted. The screening of many shrimp viruses is basically accomplished by it. For instance, detecting whether shrimp seedlings carry white spot syndrome virus (WSSV) is a common application (Ghosh et al., 2021). In some farms where equipment conditions are not so ideal, LAMP is actually more convenient. It does not require complex instruments. As long as the amplification is carried out at a constant temperature, the color change can be observed, and on-site personnel can also quickly judge the results. The situation of metagenomic sequencing is somewhat special. It does not focus on a specific pathogen but analyzes the DNA of all microorganisms in the sample together. This approach is particularly valuable when encountering diseases of unknown origin that cannot be detected by conventional tests (Wang et al., 2023). Although the cost is higher than the previous two types, it can provide key clues in sudden and unknown diseases. Combining the rapid detection of PCR and LAMP with the comprehensive analysis of metagenomics can basically establish a relatively complete framework for disease early warning and diagnosis, enabling prevention and control to be initiated earlier. 4.2 Intelligent diagnostic approaches based on imaging and behavioral monitoring In recent years, many livestock farms have begun to rely on intelligent devices such as imaging and behavior monitoring to assist in assessing health conditions. Some people set up underwater cameras in fish ponds, while others install visual sensors in net cages. Combined with machine learning algorithms, they conduct round-the-clock observations of the fish population's conditions. When fish exhibit abnormal behaviors - such as swimming slowly, eating less, changes in body color, or even swimming alone (Grieb et al., 2020) - the system often captures these subtle changes earlier than humans. High-resolution images can also capture small lesions on the body surface. Through pattern recognition technology for preliminary judgment, it also avoids the easy omission of problems during manual pond patrols. In shrimp farming, another approach has also been attempted: using underwater acoustic sensors to listen to the feeding and activity sounds of shrimp flocks. Once the sound is abnormally quiet, it may indicate stress or disease (Du et al., 2025). These intelligent tools are equivalent to providing farms with a "non-tiring assistant", which can detect early signs and reduce the risk of large-scale outbreaks.
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