After the start of autumn, the weather gradually cools down. Although the heat is still lingering, there's a period known as the "autumn tiger." However, the overall trend is that the daily temperature difference becomes more noticeable—hot during the day and cooler at night. Autumn is a critical time for aquaculture management. A single mistake can lead to significant losses or even undo all previous efforts. To ensure a successful harvest, the following key techniques and management practices are recommended:
**Water Quality Management:** As farmed species grow, pond density increases, leading to accumulation of leftover feed, excrement, and decaying aquatic plants. These materials consume oxygen and release harmful gases like hydrogen sulfide, while also increasing ammonia levels and lowering pH. This can result in fish floating head and even mass die-offs. Therefore, it's essential to perform regular water changes in small amounts, drawing from the upper and middle layers to promote plankton diversity and prevent blue-green algae blooms. Applying beneficial microorganisms such as Bacillus, photosynthetic bacteria, nitrifying bacteria, and EM liquid can help control nitrite, ammonia, and hydrogen sulfide levels. For crab ponds, gradually increase water exchange frequency, avoiding sudden high water levels that may cause floating and death. Every 10 days, apply lime (5 kg per mu) to maintain a pH between 7.8 and 8.5, with a transparency of 30–40 cm. This helps harden crab shells and supports healthy growth.
**Feeding Practices:** Improve the quality of feed for conventional fish, ensuring daily feeding is 5–6% of their body weight, with 60% animal-based feed. For shrimp, feed should be 7–8% of their body weight. Crabs require a higher proportion of animal feed (65%), with daily feeding at 10% of their total weight. From early October onward, as water temperatures drop, feeding rates should decrease gradually to 3–5% of the total weight of fish, shrimp, and crabs. During early and mid-autumn, river crabs actively feed on plants and snails, so it's crucial to ensure sufficient food sources. If plant coverage is low, supplement with additional vegetation and snails. In soft-shell turtle farming, focus on maintaining good water quality to enhance feeding activity. Use water purifiers to quickly reduce ammonia and nitrite levels, then add biological agents like photosynthetic bacteria after two days to boost beneficial microbes. Adding up to 20% fresh or chilled fish slurry to feed can improve protein and fat intake, boosting growth and fullness. Additionally, include preventive treatments like andrographis paniculata or garlic in feed for a few days to avoid enteritis.
**Disease Prevention and Control:** Historically, fish diseases tend to peak after the start of autumn. Proactive measures, such as "prevention before disease and early treatment when disease occurs," are vital for effective control. Regular disinfection using chlorine dioxide every 20 days, combined with adding detoxifiers, calcium, and oxytetracycline to feed monthly, can help manage health issues. In poor water conditions, use the "kill first, then sterilize" method: net fimbriae for shrimp and crabs, use trichlorfon for fish, and apply mixtures to the entire pond. After 3–5 days, apply quicklime (5–10 kg per acre) and rice water Quanchiposa. In late autumn, when cold air arrives, tropical species like white shrimp and Macrobrachium rosenbergii need protection against sudden temperature drops, so prepare for cold weather and implement heating measures.
**Pond Monitoring:** Regularly patrol the ponds in the morning and evening to observe fish, shrimp, and crab activities, check feeding patterns, and monitor water color, transparency, and pH. Remove rotting plants and leftover feed promptly, and clean feeding areas thoroughly. For species like river crabs and soft-shell turtles that are prone to escaping, inspect escape-proof facilities and inlet/outlet barriers. Strengthen nighttime security checks to prevent theft.
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