Rice Field Eel Farming Methods and Cost-Profit Analysis

The rice field eel, also known as changyu or shanyu, belongs to the family Synbranchidae and is distributed throughout China except on the Qinghai-Tibet Plateau. At present, artificial farming of rice field eels has the characteristics of being a mature and simple method, occupying little land, having wide feed sources, few diseases, a short cycle, quick results and high economic returns, and is one of the good projects for farmers to get rich today. So how are rice field eels farmed? Are the costs and profits high?

I. How are rice field eels farmed?

1. Building the pond

Build the farming pond in a sunny place with a certain water source and relatively solid soil. There are three types of farming ponds: mud-bottom ponds, cement ponds, and mud-structure ponds with bricks laid around the sides. For larger farming operations, cement ponds are best. The area can be 10—15 sq m, with a depth of 0.8—1 m. Set small caves in the pond walls, and spread 30 cm of pond mud on the bottom to facilitate the eels burrowing to rest. Store water to a depth of 10—15 cm. Set up water inlet and outlet openings at the water surface, using fine polyethylene mesh to prevent escape. Plant arrowhead on half the pond surface area, or cultivate duckweed and water hyacinth aquatic plants, to provide shade and concealed habitat for the eels and to prevent heatstroke. The walls of the rice field eel farming pond should be at least 30 cm above the water surface, so as to prevent the rice field eels from escaping when the rain washes over.

2. Stocking

April—August each year is the spawning season for rice field eels, with May—June being the peak period. During the spawning period, go to places where the eels live to look for eggs, use gauze to scoop up fertilized eggs or seedlings, then place the eggs in small ponds or clay jars to hatch and rear the fry. Feed the seedlings egg yolk, minced meat, bran cake powder and so on. When they grow to a tail weight of 20 grams in the same year or the next year, they can be put into the large pond to be farmed to market size. In addition, juvenile fish can also be purchased on the market and put into the pond, which makes the turnover faster. The best time to stock rice field eels is in early spring; when raised until October, the large eels can exceed 150 grams, and the small ones are around 100 grams. The best specification for stocking rice field eels is 30—40 eels per kg, and mixing large and small eels must be avoided to prevent them from killing or swallowing each other. Each square meter can hold 1—2.5 kg. Rice field eels have a strong ability to mate and reproduce on their own, so generally after the first stocking there is no need to put in more fry, but protection and management must be strengthened.

3. Feeding

Rice field eels like to eat live food and are also very greedy. In artificial rearing of rice field eels, earthworms, mussel meat and so on are all good feed; lights can also be used to attract and kill flying insects into the pond, or pig blood can be used to attract flies to lay eggs and produce maggots as feed. Earthworms are best; every 7—8 earthworms can increase eel meat by 1 gram. Rice field eels are strict in their choice of food; after being fed one kind of feed for a long time, it is very difficult to change their feeding habits in a short period. Therefore, when changing the feed variety, do not feed for the first 2—3 days, so that hunger makes them non-selective and they eat the new feed. Rice field eels are accustomed to hiding by day and coming out at night, so when first stocking, the feeding time should be at 4—5 p.m. each day, or before dark in the evening, and then the feeding time should be moved earlier day by day. After a period of bait training, they can be fed at 9 a.m. or 2 p.m. each day. An alternate-day feeding method can also be used to increase their food intake. The bait can be placed on a feeding platform made of a wooden frame or polyethylene mesh cloth; the feeding location should be fixed, and the feeding amount should be 6—7% of the fish body weight. On the day after feeding, fresh water should be exchanged to keep the water quality in the pond fresh and the dissolved oxygen content high.

4. Management

Rice field eels grow very slowly, and the suitable water temperature is 15—28°C. When the water temperature is below 15°C, it affects the feeding of rice field eels; below 10°C they stop feeding completely and enter a hibernation state. When the water temperature exceeds 28°C, the food intake of rice field eels also decreases, and measures should be taken at this time to lower the water temperature. From after spring to before the beginning of winter is the peak growing season for rice field eels; management should be strengthened, feeding them enough and well, at fixed times and in fixed amounts, so that the eels can grow faster. Leftover bait should be removed promptly. Before the beginning of winter, they must be fed enough feed. After the beginning of winter, the pond water must be drained dry and covered with rice straw, with a thickness that does not cause the rice field eels to suffocate and die, so as to protect the pond chamber and prevent the rice field eels from freezing to death due to low temperature. After spring, water should be added again at the proper time.

5. Diseases

Natural enemy control. During the growth period of rice field eels, especially when the fry have just been stocked and during the breeding season of rice field eels, ducks must never be allowed into the pond to prey on them. In summer, sometimes because the temperature is too high, rice field eels may show symptoms of heatstroke and coma; at this time, change to cool water or provide shade to lower the temperature, then feed fresh mussel meat. The main disease of rice field eels is plum-blossom spot disease; the symptom is the appearance of soybean-sized, yellow round diseased spots on the back of the rice field eels. Treatment method: some toads (laihama) can often be kept in the pond; because the bufotoxin in the toads has preventive and therapeutic effects, it can reduce the incidence of disease. If disease is found to have already occurred, the head of a skinned toad can be tied with a string and dragged back and forth in the pond several times, and the disease can be eliminated within 1—2 days.

II. Analysis of rice field eel farming costs and profits

(1) Input

1. Pond construction cost 200 yuan; purchasing 15-20 kg of wild rice field eels, calculated at 15-20 yuan per kg for medium-sized rice field eels in summer (30-50 grams per eel), requires a cost of about 300-400 yuan.

2. After 5-8 months of rearing, the body weight of rice field eels can increase by 3-5 times. We calculate based on a 3-fold weight gain, so 20 kg of rice field eels can gain 60 kg. Calculated at a feed cost of 8 yuan per 1 kg of rice field eel weight gain (in fact, using large amounts of maggots and earthworms costs far less than this), the feed cost required is 480 yuan.

3. Medicines and other expenses total 100 yuan. The above 4 items cost about 1080-1180 yuan in total.

(2) Profit

A 10 sq m farming pond yields 80 kg of large-specification rice field eels (over 100 grams per eel). Calculated at the medium price for large-specification rice field eels purchased on the market in winter and spring (40 yuan per kg), the income is 3200 yuan, and the input-output ratio is about 1:2.8. To put it more specifically, a 10 sq m farming pond can create a profit of more than 2000 yuan (200 yuan per sq m) during several months of farming. For an ordinary farming household, taking the construction of 50 farming ponds as an example, the income can reach more than 100,000 yuan.