Khanh Hoa protects farmed aquatic products amid hot season

Protecting aquaculture from heat stress

The Sub-Department of Animal Health and Production of Khanh Hoa province has urged aquaculture farmers to implement comprehensive disease-prevention measures to cope with extreme heat.

According to the Khanh Hoa Provincial Hydro-Meteorological Station, there is an 80 - 90% chance that from April to August, the El Niño -Southern Oscillation (ENSO) is likely to shift to a neutral phase. By July and August, it is expected to transition toward El Niño conditions with a 60-70% probability.

Average temperatures are forecast to be 0.5 - 1.0°C higher than the multi-year average in the same period. Heatwaves are expected to begin in April in the mountainous areas of the province's west and south. They will then expand in scope and intensity, potentially becoming more severe than in the same time in 2025. These complex weather patterns increase the risk of disease outbreaks, posing challenges for aquaculture, especially in brackish-water shrimp farming and offshore cage culture.

“Surveillance results show complex developments of dangerous pathogens in the province. For brackish water shrimp, although white spot disease (WSD) and acute hepatopancreatic necrosis disease (AHPND) have not broken out into large-scale epidemics, the pathogens remain present in the environment and often cause mortality during the 45 - 60 day farming stage. Notably, cases of Enterocytozoon hepatopenaei (EHP) infection have appeared at a relatively high rate, accounting for nearly 40% of positive samples monitored from March to August 2025,” says Tran Thanh Thuy, Deputy Head of the Sub-Department of Animal Health and Production.

In the case of cage-cultured species, lobsters continue to suffer losses from milky disease, red body disease, and black gill disease caused by fungi. Meanwhile, monitoring results for marine fish over the past two years show relatively high infection rates of Streptococcus spp. and Vibrio spp., exceeding allowable limits and tending to increase toward the end of the farming cycle, leading to ulceration and scattered mortality.

Synchronous implementation of disease prevention solutions

To minimize the risk of disease outbreaks, the Sub-Department has instructed farmers to follow the principle of “prevention is key,” enhancing proactive pathogen monitoring and biosecurity. For pond-based farming systems, pre-stocking treatment and pathogen elimination are mandatory.

Farmers should thoroughly treat pond bottoms and water sources to eliminate pathogens and prevent their introduction via the water supply. During farming, it is necessary to monitor water color and regularly check environmental parameters such as temperature, pH, and dissolved oxygen daily, as well as toxic indicators such as H₂S and NH₃ weekly for timely adjustments.

Deputy Head Tran Thanh Thuy also emphasizes the importance of feed management. Farmers need to adjust feeding rates, reducing rations by 30-50% during periods of extreme heat or localized heavy rain. Excess feed must be avoided to prevent pollution, and feeding should be prioritized in the early morning or late afternoon. To improve resistance, farmers are advised to supplement feed with vitamins, minerals, and probiotics to enhance the resilience of aquatic species.

Cooling measures such as maintaining deeper water levels, using specialized tarpaulins, or shading nets to block direct sunlight and radiation should also be applied. When abnormal signs are detected, farmers must promptly report to authorities for guidance and avoid improper antibiotic use. Farmers should also closely monitor water color to prevent algal blooms and update environmental monitoring data to take timely action, such as early harvest or cage relocation if necessary.

As for cage culture, the Deputy Head recommends selecting healthy, traceable, and quarantined fingerlings. Fresh feed must be of high quality and properly preserved. Farmers should maintain an appropriate cage depth to reduce surface heat effects and plan harvests for market size before the storm season. Regular cleaning of cage nets is mandatory to prevent injuries to aquatic species, ensure water flow, avoid stagnation, and limit pathogen accumulation.

Hot weather causes livestock to lose their immunity very quickly. If the farm buildings are not cooled down in time, diseases can arise and spread rapidly in a short period. In aquaculture, particularly for ornamental fish and freshwater aquatic species, prolonged hot weather is also causing fluctuations in pond water quality, leading to a rapid decrease in dissolved oxygen and making disease outbreaks more likely.