In addition, there was a season of large-scale fish stocking. In previous years, many fish farmers noticed that 2–7 days after releasing fingerlings, some of them would show signs of "cold" stress. These fish would float on the surface of the pond, with dull skin, excessive mucus, severe paralysis, and even death. The fingerlings were usually transferred directly from the nursery ponds to the adult fish ponds. However, due to the temperature difference between the two environments, this sudden change often caused the fish to suffer from cold shock.
Based on my own stocking experience, I will now introduce two effective methods—physical and medicinal—to prevent fish from suffering from cold stress when being moved. These techniques are also applicable for preventing cold-related issues during summer breeding and autumn fry transfers, with excellent results and no adverse effects on the fish.
**Physical Method:**
To reduce the impact of temperature differences, it is recommended to place a cage in a corner of the adult fish pond before transferring the fingerlings. When the temperature difference between the nursery and adult pond exceeds 3°C, the temperature should be gradually adjusted. Once the fish have acclimated, they can be carefully introduced into the adult pond.
The process involves adding water from the adult pond into the transport tanks or live water boats where the fish are kept. Once the water temperature in these containers matches that of the adult pond, the fish should be left in the container for 10–30 minutes. Then, the fish and water should be slowly poured into the cage. This allows the fish to adjust to the new water conditions. After staying in the cage for 1–1.5 hours, they can be safely released into the adult fish pond.
**Medicinal Method:**
Due to the fact that adult fish ponds are typically deeper and thus colder than nursery ponds, garlic and urea have been used together for a long time to prevent cold stress. This method has proven very effective with no harmful side effects.
For every 500 kg of fingerlings, 1.3 kg of garlic juice is added to the water. After the fish are placed in the transport tank or live water boat, 2.5 kg of urea is wrapped in a cotton cloth and allowed to sink to the bottom of the container. This is done once the water temperature in the tank is close to that of the nursery pond. This combination helps the fish better adapt to the new environment and reduces the risk of cold stress.
These methods not only improve fish survival rates but also ensure healthier growth and better overall performance in the adult fish ponds.
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