Key Technical Points for Raising Rice Field Eels in Spring
As the saying goes: "The whole year's work depends on a good start in spring." Doing a good job of spring management is one of the conditions for successful rice field eel farming. Below, the author discusses the key management points for raising rice field eels in spring based on practical experience:
Preparatory Work
Around Qingming, when the water temperature generally stabilizes above 10°C, preparatory work can begin. First, clean the environment around the breeding pond, then carry out chemical disinfection. The method is to make a saturated lime solution of 50 g/L using quicklime, filter out the clear liquid, add 10 g/L of caustic soda and stir evenly to make a strong alkaline disinfectant, then spray this liquid around the breeding pond for disinfection. Finally, remove the overwintering cover from the surface of the eel pond, and immediately spray the disinfectant on the mud surface and the inner walls of the pond. After completing the above work, check the overwintering condition of the rice field eels and whether the facilities of the eel pond are intact. At the same time, the mud ridges in the pond should also be repaired and planted with aquatic plants such as arrowhead, water chestnut, taro, etc.
Maintaining Water Temperature
Spring temperatures are relatively low, and sometimes a "spring cold" phenomenon occurs. Therefore, heat preservation work must be done well. Initially, the plastic film used for overwintering can be temporarily borrowed for covering; at noon on windless, sunny days, uncover the film to expose the pond for a few hours, and cover it again in the afternoon to preserve heat. If conditions permit, electric lights or other heating facilities can be used. Heating with electric lights can also enhance illumination and promote the growth and reproduction of algae, thereby achieving the purpose of inhibiting the reproduction of harmful bacteria. If there are grape vines around the eel pond, especially on top, branch thinning should be strengthened so as to make use of sunlight as much as possible.
Water Quality Management
The rice field eel is an animal that prefers shallow water and warm conditions, so in early spring the water level should be controlled at about 6 cm to help the water temperature rise. At the same time, water changing work should be done well to keep the water quality fresh, improve the appetite of the rice field eels, and enhance feed conversion. Changing water is an effective way to remove pond waste, increase dissolved oxygen, and keep water quality fresh. However, rice field eels are relatively sensitive to differences in water temperature. Once the temperature difference during water change exceeds 3°C, the rice field eels may catch a cold disease and gradually die. Therefore, when changing water, water of the same temperature should be used as much as possible. A general measure is to build an additional storage pond, and change the water after it has been exposed to the sun. The frequency of water changes should be flexibly controlled according to the stocking density of the rice field eels, feeding conditions, air temperature, etc., and the time is generally best at noon on sunny days. When the air temperature is relatively low, do not change the water. When the air temperature rises to 15°C, change the water once a week, each time replacing 1/4 of the total water volume; when the air temperature rises to about 20°C, change the water once every 5 days, each time replacing 1/30.
Timely Feeding
Feeding in early spring is mainly to restore the physical condition of the rice field eels, encourage them to come out and move about, improve their appetite, and adjust their feeding habits. According to experiments, the order of the rice field eels' olfactory sensitivity to various baits from high to low is: earthworms, clams, snails, mussels, frogs, chicken intestines, duck intestines, pig intestines, etc., and fresh live bait is best. Usually feed live earthworms; for small-scale operations, yellow mealworms can be fed. Generally, after feeding live bait for about 1 week, the rice field eels will come out in full force, and after that they can be gradually trained to feed on other types of bait. For the first feeding, the amount can be about 0.5% of the body weight of the rice field eels. On the second day, observe whether there is leftover bait; if so, reduce it as appropriate, otherwise increase the feeding amount appropriately.
Disease Prevention and Control
Under the conditions of low temperature and little light in spring, rice field eels are prone to saprolegniasis. In addition to strengthening illumination and raising the water temperature, prevention and control measures can also use a mixed solution of 0.5 g/L salt and 0.4 g/L baking soda sprinkled over the whole pond. After the disease occurs, a 0.2 mg/L malachite green or 0.3 mg/L methylene blue solution can be sprinkled over the whole pond once every 3 days, and 3 times can cure it.