How to raise the water temperature of the pond when farming yellow eels in winter

1. Building the eel pond: Choose a sunny open area, field plot, or old ditch to build the pond. To make water changes easier, it is best to build the pond where a water source is guaranteed. Cement ponds, brick ponds, rubble ponds and rammed-earth ponds are all acceptable; seal the joints with cement slurry or rammed earth, and make sure the pond bottom and all four sides do not leak and the eels cannot easily escape. The size of the eel pond depends on the scale of farming; it can be large or small, from a few square meters to several dozen square meters. Generally the pond is 20-30 sq m, with a depth of about 1 m, and the shape depends on the site. The water depth is generally kept at around 10-15 cm in spring, summer and autumn, and in winter the pond is drained leaving only rainwater. To make water changes and draining easier, open one water outlet or install an inlet/outlet pipe at both the bottom and the top of the eel pond. Also install fish screens. After the pond bottom is built so it does not leak, spread 3-5 cun of mud over it; mud made by composting river mud and green grass can be used to line the pond bottom (in some places the bottom is lined to a thickness of 60 cm). Place piles of rubble in the center or at the four corners of the pond to help the yellow eels keep warm or cool off, matching their sedentary habits. The pond water temperature is most suitable at 10-25°C. Plant trees, grow melons, or plant bamboo to build a shade frame around the pond, or plant several arrowheads, to reduce summer sunlight; aquatic plants such as water hyacinth can also be grown in the pond for the yellow eels to escape the summer heat.

2. Selecting and stocking seed: Choose good stock; yellow ones are best, blue-green ones second. It is best to contact eel farmers and buy seed eels of uniform size, strong body, and free of disease and injury; you can also buy them at the market or catch them in the wild. Seed eels of about 15-25 per jin are best. Stock them in the third and fourth months after Awakening of Insects (March 5-6). Generally stock 2?? 5-3 jin per sq m; if rearing conditions are good, about 5-10 jin can be stocked. When stocking, put one or two toads in each pond to co-cultivate, which can help prevent common yellow eel diseases, and put some loofah fiber or straw bundles into the pond so the small eels can hide. Seed eels can also be obtained from April to October by catching young eels by hand from rice fields or shallow muddy burrows (or by trapping), but when catching by hand wear gauze gloves and hold the front half of the eel between the middle and index fingers, so the young eels are not injured; young eels caught with an iron hook will have internal injuries and cannot be farmed. 3. Feeding bait: For pond-farmed yellow eels, because their range of activity is limited, bait must be supplied for intensive rearing. The yellow eels being fed eat supplied river mussel meat, snail meat, small miscellaneous fish and shrimp, livestock and poultry offal, and rice stem borers, silkworm pupae, food factory scraps, and rapeseed cake, and they especially like artificially bred earthworms and fly larvae. You can also use lamps to lure moths in, or use pig blood to attract flies to breed larvae as feed. The yellow eel is a carnivorous fish and very voracious; when bait is seriously insufficient, yellow eels may cannibalize each other or the big eat the small and the strong eat the weak. Because yellow eels do not come out to move during the day, it is best to feed at 8-10 p.m. each day. Animal bait should be the main food, with plant bait (such as bran, rice, and sour and sweet foods like melons and fruit) as a supplement. Generally feed once a day; the feeding amount is 3-5% of the yellow eel's body weight in the early stage, and as the yellow eel's body weight increases the feeding amount increases accordingly. It is best to scatter the bait evenly over the whole pond. When bait is insufficient, you can also supplement with some duckweed and mulberry leaves. Seize the golden growing season for yellow eels from after spring to before winter, and feed at the right time. To avoid the yellow eels stopping feeding, feed a mixed diet; the principle of feeding is new eels, nutrition, variety, and complete consumption. Human and livestock manure must be rotted and fermented before being sprinkled for feeding. It is strictly forbidden to use spoiled, moldy, rotten-smelling or deteriorated foods such as distiller's grains, tofu residue, and potato residue. If feeding is done at fixed times and places, it is convenient for the eels to eat and for manual catching. On the morning after feeding, clear away leftover bait or add new pond water to keep more oxygen in the pond. Of course, the amount of bait must also be moderate; too much will worsen the water quality, and too little will mean insufficient food. 4. Careful management: In management, carry out the “three checks and three preventions”. First, check the water condition, keep the water fresh and clear, and keep the pond clean and hygienic. Observe frequently; if the water smells slightly foul or is abnormal, change the water immediately. Where the water source is poor, change the water once every 5-8 days; change it frequently with the seasons, and when the weather is hot and the water temperature is too high, also build a shade frame for cover or appropriately deepen the water level. In winter, change the water as little as possible. Some loaches can be co-cultured in the pond, 1-2 jin per sq m, to improve water quality and prevent yellow eels from tangling around each other. Second, check the bait condition; pay attention to observing shortage of bait, single bait, and mixed bait. When there is thunder and rain and a shortage of bait, yellow eels may be startled and escape outward, not eat, and not enter their burrows; when bait is short, yellow eels may chase the small and eat each other. When switching to new bait, go from little to more. Third, check for disease; as long as prevention is done in advance and observation is careful, eel diseases can be controlled. The “three preventions” are: first, prevent escape; build the pond firmly to prevent floods from bursting the pond or the eels from climbing over the pond, and drain water during thunderstorms to prevent escape. Second, prevent harm; geese and ducks must not enter the pond. Third, prevent poisoning; it is strictly forbidden for cigarette butts, chemical fertilizers, pesticides or polluted water to enter the pond. Chemical fertilizers and pesticides in particular are violently lethal to fish. Once poisoning is found, thoroughly drain the pond water, and use fresh water to flush and replace the toxic water and filth in the pond. Then mash garlic and mix it with water, putting 5 g per sq m into the pond, to avoid mass death of yellow eels. 5. Disease prevention and treatment: Common yellow eel diseases include fever disease, cold disease, skin toxin disease and capillary worm disease. Fever disease is caused by excessive density of yellow eels. The prevention and treatment method is to co-culture a small number of loaches in the pond (1 loach for every 200 yellow eels is suitable). When yellow eels become ill, change the water immediately, or add a 7-in-10,000 copper sulfate solution to the pond, sprinkling about one large liang per sq m. Yellow eel cold is caused by the new water being too low in temperature. Before changing water with very low-temperature spring water, well water, mountain mine water or reservoir water, let the water temperature rise before putting it into the pond. In late autumn and early winter, when the water temperature drops below 12°C, yellow eels begin to enter the mud to spend the winter at a depth of about 30 cm. At this time, drain the pond water, keep only the mud moist, and cover the mud with a layer of straw about 5 cun thick to prevent freezing and avoid ice forming. The appearance of plum-blossom spots the size of soybeans or broad beans on the back of yellow eels is a common disease of yellow eels. The preventive method is to regularly put some toads in the eel pond, because the secretions on the toads' bodies have the effect of preventing this disease. If the yellow eels already have this disease, immediately take 1-2 skinned toads, tie them with string, and drag them a few times through the pond, and the disease can be cured. Skin toxin disease is caused by mold infection of wounds resulting from yellow eels biting each other or being attacked by harmful organisms. Diseased eels grow “white hair” on the body, lose appetite, become thin and weak, and die. Before the yellow eels are put into the pond, quicklime should be used to clear the pond and disinfect it. If diseased eels are found, a mixture of 4-in-10,000 salt and baking soda can be sprinkled over the whole pond.