Key points of artificial breeding technology of snails in Huai'an, Jiangsu Province
_Fei Xiangdong
Sinotaia quadrata, belonging to the mollusc phylum, gastropods, mid-gastropods, snail family, ring snail genus, commonly known as snails, its delicious taste, rich in nutrition, with high edible and medicinal value. In recent years, JiangBa Town, Hongze District, Huai'an City, Jiangsu Province, has worked hard to create the "Jiangba Snail" brand, and held the Snail Festival for 5 consecutive years. "JiangBa snail" is the top product of the snail, has obtained the Ministry of Agriculture and Rural Affairs organic snail certification certificate, its body is thin, fat and tender, full of tendons, known as "civilian abalone" reputation. In 2020, Jiangba Town adopted the business model of "company + base + farmer", established the Jiangba Xiaodonghu snail breeding demonstration base with "Jiangba snail" as the core product, implemented a variety of breeding modes such as ponds and rice fields, and achieved significant economic and social benefits.
1 Water source conditions
The base cites the water source of Hongjin Irrigation District of Hongze Lake, the water quality is fresh, the amount of water is sufficient, and there is no pollution source around. The water quality of aquaculture water meets the requirements of the Fishery Water Quality Standard (GB 11607-1989).
2 Pond conditions
Snails have strong adaptability to the growth environment, like the warm winter and cool summer growth environment and soft substrate, there are not too many requirements for pond conditions, can be shallow ponds and drainage ditches, can also be rice field depressions, generally have mud and water to survive. The water environment and substrate of ponds and paddy fields in the Xiaodonghu Snail Breeding Demonstration Base meet the requirements of the Environmental And Technical Conditions for Green Food Production Areas (NY/T 391-2000).
2.1 Pond transformation
The existing shallow pond depression in Xiaodong Lake is used for transformation, and the pond soil is clay loam soil, and the pond area is 0.1~4 hm 2. Small ponds are not more than 20 m wide, and large ponds choose to build simple trestles for keepers to walk around and feed every 20 m in the pond, or to excavate rowing ring ditches with a width of 2 m and a depth of 0.8 m every 20 m in the pond to facilitate the feeding of bait. A number of small snail ponds can be transformed side by side, the embankment slope ratio is 1:2.5~1:3, the pond depth is 0.8~1.2 m, the bottom retains 10~15 cm silt, the pond is set at the opposite corner of the inlet and drainage, and the anti-escape net is installed.
2.2 Transformation of rice paddies
Using some low-lying paddy fields in Xiaodonghu Lake for transformation, the mud at the bottom of the paddy field is soft, the circular ditch excavated in the field is 50 cm wide and deep, or the "well" "eye" and "field" glyph ditch, the water depth of the paddy field is 15 to 25 cm, the height of the field is 40 cm, and the anti-escape net is installed in the inlet and drainage outlets.
3 Clear pond fertilizer water
The remodeled pond or rice field needs to be fully cleared and disinfected with quicklime or bleach powder, of which quicklime is the best. When there is no water, use 75 kg of quicklime per 667 m2, and sprinkle the pond or rice field after water is dissolved; when there is water, use 150 kg of quicklime per 667 m2 and 1 m water depth, and sprinkle it after water to achieve the effect of clearing the wilderness, killing germs, increasing pH and increasing calcium. After 7 days of clearing the pond, apply fermented and decomposed livestock and poultry manure as the base fertilizer for fertilizer water, apply 200 to 400 kg per 667 m2, if the bottom mud fertilizer, the amount of use can be reduced, the bottom mud is thin, the amount can be increased.
4 seedlings are stocked
4.1 Farming patterns
At present, the xiaodong lake snail breeding demonstration base mainly has pond nesting, rice field nesting and other modes. The main varieties are grass carp, crucian carp, bream and other herbivorous fish species or silver carp, bighead carp, loach and so on. Aquatic plants such as white, lotus or water hyacinth can be rarely planted in the pond to shade the snails from the heat, facilitate their climbing and roosting, and provide bait.
4.2 kinds of snails are delivered
The selection criteria for snails are robust, disease-free, no parasites, short and swollen tips, smooth and ribbed shell surfaces, nearly oval shell mouths, yellow-brown patches, and the snail head can quickly retract back into the shell when frightened, and the size of the snails is about 150/kg. Breed snails should be stocked before stocking a small amount of snails or fry to test the water, the main pond stocking time is best completed in the early stage of snail breeding, the stocking amount of seed snails per 667 m2 is 20 to 30 kg, the number of juvenile snails per 1 m2 stocking is 1 000, the stocking of silver carp and bighead carp fingerlings per 667 m2 is 150, the ratio of silver carp and bighead carp is 2:1, or with grass carp, crucian carp and bream, and the number of fry stocked per 667 m2 is 0.3 million to 0.5 million. Rice field nesting can be directly stocked with young snails after the seedlings return to green, and the stocking density is half of the stocking density of the main pond.
4.3 Breeding of snails
Snails and crucian carp ovulation methods are more similar, that is, ovulation in batches, snails begin to breed in April every year, May to September is the peak season for growth, the number of litters is related to the age of snails and environmental conditions, generally each fetus can produce 3 to 7 snails. Juvenile snails generally begin to forage after 2 to 3 weeks of birth, plankton can not fully meet the growth needs of snails, at this time should be artificially assisted feeding, the use of soy milk, compound feed or vegetable cake detritus for feeding, feeding principles a small number of times, and try to keep the pool water micro-flowing.
5 Daily management
5.1 Feed feeding
Snail feed sources are relatively wide, in the main pond snail in addition to eating natural food, can be properly fed soybean meal or artificial compound feed, bait requirements fresh and nutritious, in line with the "pollution-free food fishing compound feed safety limit" (NY 5072-2002) provisions. Feeding time and method: when the water temperature is 20 ~ 28 °C, the snail feeding is strong, can be fed twice a day (once in the morning and once in the evening), each feeding amount is 1% to 3% of the body mass; when the water temperature < 15 °C or > 30 °C, it is less or no. Due to the slow movement of the snails and the lack of foraging, it is advisable to feed them evenly throughout the pond. When using extensive culture, fermented organic fertilizer or biological fertilizer can be applied at regular intervals to meet the growth needs of snails.
If the snail piece is found to be deep in the shell during production, which is caused by hunger, indicating that the bait is insufficient, the protein content of the bait should be increased at this time, and the number of baits should be increased. If it is found that the snail's pieces are irregular and there is a fleshy overflow phenomenon when shrinking, indicating that the snail is deficient in calcium, shell powder and bone meal should be added to its bait to increase calcium.
5.2 Water Quality Management
The water quality of the snail pond should be kept fat and tender, and new water should be filled regularly, the deepest part of the pond water should not exceed 80 cm, the transparency of the water body should be 25 to 30 cm, and the dissolved oxygen should be >4 mg/L. A pH of around 7.5 is the most suitable for snail growth, when the pH of the pond water is low, the application of quicklime is applied to improve, and after a week, emus bacteria are sprinkled to ensure good water quality.
5.3 Disease control
Snail disease is mainly to prevent, generally with quicklime, fungicide or bait for prevention and treatment, prevention and control drugs should comply with the provisions of the "Green Food and Fishery Drugs Use Guidelines" (NY/T 755-2013). Quicklime can effectively prevent snail disease, while increasing the calcium in the water body, promoting the growth of snails. When treating diseases such as snail ciliate, it is necessary to avoid the use of copper sulfate as much as possible, which has a killing effect on snails. Rice farming should avoid the harm caused by pesticides and fertilizers, and use drugs and doses according to regulations so as not to affect the growth of snails. It is necessary to strengthen the patrol of ponds, and the invasion of natural enemies such as snakes, rats, ducks, and birds should be dealt with in a timely manner.
5.4 Wintering management
Before entering the winter, the cultivation should be strengthened to make the snail robust, when the water temperature < 10 °C, the snail will hibernate in the silt, leaving a small hole in the surface of the silt for breathing. After wintering, the water is deepened to more than 60 cm to keep warm, and some chopped straw is sprinkled on the pond to facilitate the snail to overwinter, and the snail does not eat during the winter, do not use bait, but maintain the depth of the pond, change the water regularly, and ensure that the dissolved oxygen in the water is sufficient.
6 catches and harvests
Artificially farmed snails can reach 4 to 8 g edible snail specifications that year, in accordance with the principle of catching large and leaving small, from March to April, the large snails (seed snails) are first caught and listed, and after July, the snails that reach the edible specifications are gradually caught. According to the snail growth situation of about 30 d, the pond round is released, and attention is paid to selecting some female snails to achieve natural replanting.
6.1 Fishing Methods
More effective fishing methods: one is to choose a certain mesh round or square mesh pieces to make a net pocket, surrounded by bamboo pieces, etc., the net pocket is placed close to the pond bottom mud, the middle bait is thrown, the snail is lured into the net, the catch is large and small; the second is to put bamboo branches, grass handles, nets and other climbing objects into the pond according to the habit of the snails, and collect them the next morning; the third is to use the net to actively harvest or pick up the dry pond.
6.2 Transport and Storage
With straw bales, woven bags, tote boxes, etc., the means of transport should be strictly disinfected, no odor. When loading the car, according to the transportation time and the heat preservation of the carriage, a layer of crushed ice is added between each layer to improve the survival rate of transportation, avoid accumulation too high, squeeze the bad snail shell, and keep the snail moist during transportation, and strictly prevent wind, sun and rain. Snails are suitable for storage at a temperature of 4~7 °C.
7 Benefit analysis
In 2020, the area of snail ponds and rice paddy fields in Jiangba Town will be nearly 7 million m2, the increase in the aquaculture area per 667 m2 will increase by about 2 000 yuan, and the output of the main snail pond will reach 3 000 kg per 667 m2, and the industrial production of snails has become an important way for fishermen to get rich. Rational transformation of low-yield fish ponds and rice paddies for snail nesting can promote fishery income and efficiency. From the analysis of several large-area pond mouth culture in the Xiaodonghu snail breeding demonstration base of Jiangba, the large water surface culture of snails can not only play the water purification function of snails, but also make full use of water resources.
Snail breeding ability is relatively strong, when catching snails, choose to retain the appropriate amount of snail parents for breeding, and strengthen the breeding period management and breeding of young snails, you can do a good job of seed retention, the next year can not need to buy seedlings to replant.