A method for grading culture of procambarus clarkii

Abstract

The application provides a grading culture method of procambarus clarkii, and relates to the technical field of procambarus clarkii culture.The method comprises the following steps: setting a screen near one side of a ridge in a paddy field, enclosing the screen and the ridge to form a closed temporary breeding area for seedlings; piling oyster shell broken pieces with biofilm on the bottom of the first screen in the temporary breeding area to form a biofilm area; before the seedlings are put in, putting bacillus subtilis in the temporary breeding area, and then putting the procambarus clarkii seedlings in the temporary breeding area when the water quality is stable; after 20-25 days of culture, removing the screen to make the seedlings be scattered in the paddy field until the product shrimp is harvested.The method matches the development rhythm of the shrimp body through grading culture, realizes the transition of concentrated observation and autonomous diffusion of the seedlings, and avoids the stress of transfer; the oyster shell biofilm continuously degrades the residual bait and organic waste, inhibits harmful bacteria, and stabilizes the water quality.The method can significantly improve the feed utilization rate, make the product shrimp uniform in size, high in survival rate, and improve the quality of shrimp meat.

Description

Technical Field

[0001] This invention relates to the field of red swamp crayfish farming technology, and particularly to a graded farming method for red swamp crayfish. Background Technology

[0002] Rice-crayfish integrated farming is an ecological farming model in my country that combines freshwater aquaculture with rice cultivation. It achieves the comprehensive benefits of "dual use of water and double harvest from one field" by cultivating rice and raising red swamp crayfish in the same paddy field. In red swamp crayfish farming, the rearing method during the larval stage directly determines the yield and quality of the adult crayfish. Larvae have weak activity levels, lack resilience, and are highly dependent on the rearing environment. To address the challenges of larval management, some farmers use independent enclosed net cages or temporary holding cages for centralized rearing of larvae. Once the larvae reach a certain size, they are released into the paddy field as a whole, and subsequent feeding is done by broadcasting feed throughout the pond. However, these enclosed net cages or temporary holding cages are closed structures. After the shrimp larvae grow to a certain size in the net cages, they need to be manually caught, transported, and released into the paddy fields. This process is cumbersome, labor-intensive, and the mechanical collisions, lack of oxygen out of the water, and sudden temperature changes during the catching and transport process can cause serious stress damage to the shrimp larvae, which can easily lead to problems such as detachment of appendages, shell damage, or even death. Summary of the Invention

[0003] Therefore, the purpose of this invention is to propose a graded farming method for red swamp crayfish, which can achieve a technical solution for graded cultivation and smooth transition of crayfish larvae. The technical solution of this invention is implemented as follows: 1. A method for graded culture of Procambarus clarkii, characterized by comprising the following steps: S1: Set up a partition net on one side of the paddy field near the embankment to enclose the field and form a closed seedling temporary rearing area; pile up oyster shell fragments with biofilm attached along the bottom of the primary partition net in the temporary rearing area to form a biofilm area. S2: Before releasing the larvae, Bacillus subtilis agent is added to the temporary holding area every 3-4 days. After the water quality has stabilized for 10-15 days, larvae of Procambarus clarkii are released into the temporary holding area. S3: After 20-25 days of rearing, remove the netting to allow the shrimp larvae to roam freely in the paddy field until the adult shrimp are harvested.

[0004] A further embodiment is that the preparation method of the oyster shell fragments with biofilm includes: crushing and disinfecting oyster shells, using them as a carrier, adding them to LB medium, then inoculating them with Bacillus subtilis cultured to the logarithmic phase, and after a mature biofilm forms on the surface of the carrier, adding culture water and continuing to culture for 20-30 h, then adding culture water again and continuing to culture for 20-30 h to obtain oyster shell fragments with biofilm.

[0005] A further proposed approach is that, based on the volume of the culture medium, the inoculation amount of the Bacillus subtilis solution is 2% v / v - 3% v / v; The amount of culture water added is 30% v / v - 40% v / v, based on the volume of the culture medium. The viable count of the Bacillus subtilis liquid is ≥2×10⁻⁶. 8 CFU / mL.

[0006] This invention constructs a biofilm purification zone by piling up oyster shell fragments coated with Bacillus subtilis biofilm along the bottom of the primary mesh in the shrimp larvae rearing area. The oyster shell fragments have a loose, porous structure and a large specific surface area, providing an ideal carrier for microbial attachment and proliferation. After being cultured to form a mature Bacillus subtilis biofilm, the biofilm can degrade uneaten feed and shrimp larvae metabolic waste in the rearing area, reducing the accumulation of organic waste. Furthermore, Bacillus subtilis can competitively inhibit the reproduction of pathogens, reducing the incidence of diseases in shrimp larvae.

[0007] This invention involves pre-culturing oyster shell fragments with attached biofilms and placing them at the bottom of a primary mesh in the holding area. This stabilizes the biofilm while also helping the biofilm adhere to the mesh, making the mesh a new carrier. This increases the biofilm's surface area for water purification, significantly reduces the environmental oxidative stress experienced by the shrimp, and further enhances the oxidative stress resistance of the red swamp crayfish, thus helping to maintain the freshness and quality of the shrimp meat.

[0008] In addition, the introduction of a certain amount of Bacillus subtilis agent into the temporary holding area can effectively regulate water quality and improve the bottom sediment environment by using a certain area of ​​oyster shell fragments as a colonization carrier, thus playing a role in stabilizing water quality.

[0009] A further option is that, in step S1, the biofilm area is a stacked area of ​​oyster shell fragments piled up along the bottom of the primary mesh, with a width of 8-12 cm and a height of 2-3 cm.

[0010] A further step is that, in step S1, the juvenile red swamp crayfish have a body length of 0.8–1.2 cm and a stocking density of 800–1200 crayfish / m². 3 ; In step S1, the dosage of Bacillus subtilis agent is 2-3 g / m³. 3 ...

[0011] A further option is that, in step S1, a secondary partition net is set outside the partition net, and the secondary partition net and the paddy field ridge enclose a sub-adult rearing area including a temporary rearing area; after 20-25 days of rearing, the partition net is removed, allowing the shrimp larvae to continue to be reared in the sub-adult rearing area until they reach a body length of 5-6 cm.

[0012] A further approach is to remove the secondary mesh when the shrimp larvae reach a length of 5-6 cm, allowing them to be raised freely in the paddy fields. Once they reach a length of 10-12 cm, they can be harvested to obtain adult shrimp.

[0013] This invention features a two-tiered netting system that, together with the paddy field ridges, encloses a progressively expanding aquaculture area. The first-tier netting forms a temporary rearing area for shrimp larvae, facilitating concentrated observation and precise feeding of the larvae. Compared to the entire paddy field, this temporary rearing area is smaller, making water quality easier to manage. Oyster shell fragments with attached biofilms, obtained through pre-cultivation, are placed at the bottom of the first-tier netting within the temporary rearing area, further ensuring environmental stability. This allows the shrimp larvae to receive even feeding and sufficient nutrition, providing a favorable growth and metabolic environment for adult shrimp and enhancing the antioxidant capacity of the adult shrimp's hepatopancreas.

[0014] After the primary netting is removed, the shrimp larvae enter a larger sub-adult rearing area enclosed by secondary netting, which includes the original temporary rearing area. The rearing space expands synchronously with the increase in shrimp size. Once the shrimp larvae reach a body length of 5-6 cm and their activity level and resistance significantly increase, the secondary netting is removed, allowing the shrimp to be released into the entire paddy field for free-range rearing. This progressive expansion of the rearing space, matched to the developmental rhythm of shrimp larvae, sub-adults, and adults, effectively improves feed utilization, ensures uniform feeding, promotes uniform growth, guarantees convenient management during the larval stage, and fully meets the activity space requirements of adult shrimp.

[0015] A further approach is to feed the shrimp at 4% to 6% of their total body weight during the sub-adult rearing stage, while maintaining dissolved oxygen levels ≥ 5.5 mg / L.

[0016] A further proposed solution is to feed the shrimp at 6% to 8% of their total body weight during the temporary holding area, while maintaining dissolved oxygen levels at ≥6 mg / L. When free-range, the amount of feed should be 3% to 4% of the total body weight of the shrimp, and the dissolved oxygen level should be maintained at ≥5 mg / L.

[0017] A further approach is to feed them 2-3 times a day.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a graded culture method for Procambarus clarkii, which uses pre-cultured oyster shell fragments with attached biofilms combined with a closed seedling rearing area formed by a primary net. This net-enclosed-biofilm culture method matches the developmental rhythm of shrimp larvae, sub-adults to adults, effectively improving feed utilization, uniform feeding, uniform growth, and increasing the proportion of shrimp reaching the standard size (weight ≥30 g / tail). It also enhances the oxidative stress capacity of Procambarus clarkii, further improving the survival rate and meat quality of adult shrimp. By confining the shrimp larvae within a certain area through net enclosure, it is easier to observe their feeding and growth. Furthermore, compared to the entire paddy field, the smaller size of the rearing area makes water quality easier to manage. Graded culture better ensures environmental stability, resulting in uniform feeding and sufficient nutrition for the shrimp larvae, providing a good growth and metabolic environment for adult shrimp. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0021] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0022] The feed used in this invention is Tongwei Feed from Tongwei Co., Ltd.; Bacillus subtilis was purchased from Weifang Ruichen Biotechnology Co., Ltd.

[0023] Cultivating biofilms: Oyster shells were crushed and sterilized. The crushed oyster shells were used as a carrier and added to LB medium. Bacillus subtilis culture (viable count ≥ 2 × 10⁻⁶) was inoculated at a 2% v / v inoculum and cultured to the logarithmic growth phase. 8 (CFU / mL) After a mature biofilm forms on the carrier surface, culture water is added at a ratio of 30% v / v, and culture is continued for 24 h. Then, culture water is added again at a ratio of 30% v / v, and culture is continued for 24 h to obtain oyster shell fragments with attached biofilm.

[0024] LB medium: 10 g peptone, 5 g yeast extract, 10 g NaCl, 1 L distilled water.

[0025] Example 1 The steps for graded farming of Procambarus clarkii are as follows: (1) Setting up a primary separation network and biofilm A primary netting is installed on one side of the paddy field near the embankment, forming a closed seedling temporary rearing area by enclosing the field embankment with the netting.

[0026] Before releasing the seedlings, pile up oyster shell fragments with biofilm attached along the bottom of the primary partition net in the temporary rearing area, forming a biofilm area approximately 10 cm wide and 2-3 cm high. Every 3-4 days, inject Bacillus subtilis agent along the primary partition net in the temporary rearing area at a rate of 2-3 g / m². 3 After the water quality has stabilized for 10 days, the seedlings can be introduced.

[0027] Red swamp crayfish larvae (0.8-1.2 cm in body length) were introduced at a density of 1000 larvae / m². 3 The density was placed in the temporary holding area; Feed the juvenile shrimp with a special formulated feed twice a day, at a rate of 6%-8% of the total weight of the shrimp larvae. Feed the shrimp larvae in a concentrated manner on the feeding platform to avoid spreading. Maintain dissolved oxygen levels ≥6 mg / L.

[0028] (2) Set up a secondary mesh A secondary net is set up outside the primary net to form a secondary sub-adult breeding area that includes a temporary holding area, together with the paddy field ridges.

[0029] After being raised in captivity for 20 days, the shrimp larvae grow to a body length of 2-3 cm. The first-level separating net is then removed, and they enter the sub-adult stage of cultivation.

[0030] Feed the sub-adult special feed along the edge of the paddy field twice a day, at a rate of 4%-6% of the total body weight of the shrimp; Maintain dissolved oxygen levels ≥ 5.5 mg / L.

[0031] (3) Removal of nets and free-range farming Once the shrimp larvae have grown to 5-6 cm in length, remove the secondary mesh and allow them to be raised freely in the paddy field.

[0032] The shrimp were fed along the dikes and ditches, using a special feed for adult shrimp. They were fed twice a day, with the amount being 3%-4% of the total weight of the shrimp in the pond.

[0033] Maintain dissolved oxygen levels ≥5 mg / L.

[0034] When the shrimp larvae grow to 10-12 cm in length, they can be harvested to obtain the finished Procambarus clarkii.

[0035] Example 2 The steps for graded farming of Procambarus clarkii are as follows: (1) Setting up a primary separation network and biofilm A primary netting is installed on one side of the paddy field near the embankment, forming a closed seedling temporary rearing area by enclosing the field embankment with the netting.

[0036] Before releasing the seedlings, pile up oyster shell fragments along the bottom of the primary partition net in the temporary rearing area, forming a biofilm area approximately 10 cm wide and 2-3 cm high. Every 3-4 days, inject Bacillus subtilis agent along the primary partition net in the temporary rearing area at a rate of 2-3 g / m². 3 After the water quality has stabilized for 10 days, the seedlings can be introduced.

[0037] Red swamp crayfish larvae (0.8-1.2 cm in body length) were introduced at a density of 1000 larvae / m². 3 The density was placed in the temporary holding area; Feed the juvenile shrimp with a special formulated feed twice a day, at a rate of 6%-8% of the total weight of the shrimp larvae. Feed the shrimp larvae in a concentrated manner on the feeding platform to avoid spreading. Maintain dissolved oxygen levels ≥6 mg / L.

[0038] (2) Removal of nets and free-range farming After being raised in captivity for 20 days, the shrimp larvae grow to a body length of 2-3 cm. The separating net is then removed, and they enter the sub-adult stage of cultivation.

[0039] During the sub-adult rearing stage, feed the shrimp with special feed for sub-adults along the edge of the paddy field twice a day, at a rate of 4%-6% of their total body weight. Maintain dissolved oxygen levels ≥ 5.5 mg / L.

[0040] Once the shrimp larvae grow to 5-6 cm in length, they enter the adult shrimp farming stage.

[0041] During the adult shrimp farming stage, the shrimp are fed along the dikes and ditches, using special feed for adult shrimp. They are fed twice a day, with the amount being 3%-4% of the total weight of the shrimp in the pond.

[0042] Maintain dissolved oxygen levels ≥5 mg / L.

[0043] When the shrimp larvae grow to 10-12 cm in length, they can be harvested to obtain the finished Procambarus clarkii.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not include a tiered aquaculture system, as detailed below: 1000 tails / m 3 The stocking density is controlled, and independent closed net cages are used to cultivate shrimp larvae in a concentrated manner during the seedling stage. After the shrimp larvae grow to a body length of 2-3 cm, they are transferred to paddy fields for further cultivation.

[0045] During the sub-adult rearing stage, feed the shrimp with special feed for sub-adults along the edge of the paddy field twice a day, at a rate of 4%-6% of their total body weight. Maintain dissolved oxygen levels ≥ 5.5 mg / L.

[0046] Once the shrimp larvae grow to 5-6 cm in length, they enter the adult shrimp farming stage.

[0047] During the adult shrimp farming stage, the shrimp are fed along the dikes and ditches, using special feed for adult shrimp. They are fed twice a day, with the amount being 3%-4% of the total weight of the shrimp in the pond.

[0048] Maintain dissolved oxygen levels ≥5 mg / L.

[0049] When the shrimp larvae grow to 10-12 cm in length, they can be harvested to obtain the finished Procambarus clarkii.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that no biofilm is used, as detailed below: (1) Set up a primary mesh A primary netting is installed on one side of the paddy field near the embankment, forming a closed seedling temporary rearing area by enclosing the field embankment with the netting.

[0051] Red swamp crayfish larvae (0.8-1.2 cm in body length) were introduced at a density of 1000 larvae / m². 3 The density was placed in the temporary holding area; Feed the juvenile shrimp with a special formulated feed twice a day, at a rate of 6%-8% of the total weight of the shrimp larvae. Feed the shrimp larvae in a concentrated manner on the feeding platform to avoid spreading. Maintain dissolved oxygen levels ≥6 mg / L.

[0052] (2) Set up a secondary mesh A secondary net is set up outside the primary net to form a secondary sub-adult breeding area that includes a temporary holding area, together with the paddy field ridges.

[0053] After being raised in captivity for 20 days, the shrimp larvae grow to a body length of 2-3 cm. The first-level separating net is then removed, and they enter the sub-adult stage of cultivation.

[0054] Feed the sub-adult special feed along the edge of the paddy field twice a day, at a rate of 4%-6% of the total body weight of the shrimp; Maintain dissolved oxygen levels ≥ 5.5 mg / L.

[0055] (3) Removal of nets and free-range farming Once the shrimp larvae have grown to 5-6 cm in length, remove the secondary mesh and allow them to be raised freely in the paddy field.

[0056] The shrimp were fed along the dikes and ditches, using a special feed for adult shrimp. They were fed twice a day, with the amount being 3%-4% of the total weight of the shrimp in the pond.

[0057] Maintain dissolved oxygen levels ≥5 mg / L.

[0058] When the shrimp larvae grow to 10-12 cm in length, they can be harvested to obtain the finished Procambarus clarkii.

[0059] Comparative Example 3 The difference between this comparative example and Example 1 is that Bacillus subtilis agent was directly added to the aquaculture water, as detailed below: (1) Set up a primary mesh A primary netting is installed on one side of the paddy field near the embankment, forming a closed seedling temporary rearing area by enclosing the field embankment with the netting.

[0060] Before releasing the seedlings, apply Bacillus subtilis agent along the primary partition netting in the temporary rearing area every 3-4 days, at a rate of 2-3 g / m². 3 After the water quality has stabilized for 10 days, the seedlings can be introduced.

[0061] Red swamp crayfish larvae (0.8-1.2 cm in body length) were introduced at a density of 1000 larvae / m². 3 The density was placed in the temporary holding area; Feed the juvenile shrimp with a special formulated feed twice a day, at a rate of 6%-8% of the total weight of the shrimp larvae. Feed the shrimp larvae in a concentrated manner on the feeding platform to avoid spreading. Maintain dissolved oxygen levels ≥6 mg / L.

[0062] (2) Set up a secondary mesh A secondary net is set up outside the primary net to form a secondary sub-adult breeding area that includes a temporary holding area, together with the paddy field ridges.

[0063] After being raised in captivity for 20 days, the shrimp larvae grow to a body length of 2-3 cm. The first-level separating net is then removed, and they enter the sub-adult stage of cultivation.

[0064] Feed the sub-adult special feed along the edge of the paddy field twice a day, at a rate of 4%-6% of the total body weight of the shrimp; Maintain dissolved oxygen levels ≥ 5.5 mg / L.

[0065] (3) Removal of nets and free-range farming Once the shrimp larvae have grown to 5-6 cm in length, remove the secondary mesh and allow them to be raised freely in the paddy field.

[0066] The shrimp were fed along the dikes and ditches, using a special feed for adult shrimp. They were fed twice a day, with the amount being 3%-4% of the total weight of the shrimp in the pond.

[0067] Maintain dissolved oxygen levels ≥5 mg / L.

[0068] When the shrimp larvae grow to 10-12 cm in length, they can be harvested to obtain the finished Procambarus clarkii.

[0069] Test case (1) Crawfish were cultured in rice-crayfish paddy fields for 65 days, and indicators were measured after the culture was completed.

[0070] Table 1. Breeding effects of each group

[0071] Note: Survival rate = (final number of shrimp tails / initial number of shrimp tails) × 100; Weight difference coefficient (%) = (standard deviation / mean) × 100; Feed conversion ratio = total amount of feed fed / weight gain.

[0072] As shown in Table 1, Example 1 performed well in all indicators. In terms of survival rate, Example 1 had a survival rate of 90.5%. By skipping the secondary cultivation stage and directly transferring the shrimp to open water, the sub-adult shrimp experienced greater environmental stress, resulting in a higher mortality rate. In terms of the percentage of shrimp weighing ≥30g, Example 1 had a survival rate of 89.0%, which was 20.5% higher than Comparative Example 1. In terms of weight difference coefficient, Example 1 had a weight difference coefficient of only 8.5%, indicating that the size of the adult shrimp was highly uniform, while Comparative Example 1 had a weight difference coefficient as high as 18.6%, indicating that the size of the adult shrimp was uneven and the marketable rate was low. In terms of feed conversion ratio, Example 1 had a lower feed conversion ratio, which effectively improved feed utilization efficiency.

[0073] (2) 100 adult shrimp were randomly selected from each paddy field for antioxidant index determination. The total antioxidant capacity was determined using a reagent kit from Nanjing Jiancheng Biotechnology Research Institute.

[0074] Table 2. Effects of each group on the antioxidant capacity of Procambarus clarkii

[0075] Note: The test sites are the liver and pancreas.

[0076] Table 2 shows that different farming methods have different antioxidant capacities for Procambarus clarkii. Among them, Example 1 has the highest total antioxidant capacity, followed by Comparative Example 3, and then Comparative Example 2. This indicates that the oxidative stress capacity of Procambarus clarkii can be improved by combining pre-cultured oyster shell fragments with biofilm with a closed seedling rearing area formed by a primary mesh.

[0077] This invention utilizes pre-cultured oyster shell fragments with attached biofilm, placed at the bottom of a primary separator in the temporary holding area. This purifies the aquaculture water, reduces the accumulation of organic waste, and lowers the environmental oxidative stress experienced by the shrimp. While stabilizing the biofilm, placing the biofilm-attached oyster shell fragments in the primary separator also helps the biofilm adhere to the separator, making the separator a new carrier. Compared to the entire paddy field, the temporary holding area is smaller, water quality is easier to manage, and graded aquaculture better ensures environmental stability. This allows shrimp larvae to receive even feeding and sufficient nutrition, providing a good growth and metabolic environment for adult shrimp. It also enhances the antioxidant capacity of the adult shrimp's hepatopancreas, reduces lipid peroxidation damage, improves disease and stress resistance, and helps maintain the freshness and quality of the shrimp meat.

[0078] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for graded culture of Procambarus clarkii, characterized in that, Includes the following steps: S1: Set up a partition net on one side of the paddy field near the embankment to enclose the field and form a closed seedling temporary rearing area; pile up oyster shell fragments with biofilm attached along the bottom of the primary partition net in the temporary rearing area to form a biofilm area. S2: Before releasing the larvae, Bacillus subtilis agent is added to the temporary holding area every 3-4 days. After the water quality has stabilized for 10-15 days, larvae of Procambarus clarkii are released into the temporary holding area. S3: After 20-25 days of rearing, remove the netting to allow the shrimp larvae to roam freely in the paddy field until the adult shrimp are harvested.

2. The graded aquaculture method according to claim 1, characterized in that, The method for preparing the oyster shell fragments with biofilm includes: crushing and disinfecting oyster shells, using them as a carrier, adding them to LB medium, then inoculating them with Bacillus subtilis cultured to the logarithmic phase, and after a mature biofilm forms on the surface of the carrier, adding culture water and continuing to culture for 20-30 h, then adding culture water again and continuing to culture for 20-30 h to obtain oyster shell fragments with biofilm.

3. The graded aquaculture method according to claim 2, characterized in that, The inoculation amount of the Bacillus subtilis solution is 2% v / v - 3% v / v, based on the volume of the culture medium. The amount of culture water added is 30% v / v - 40% v / v, based on the volume of the culture medium. The viable count of the Bacillus subtilis liquid is ≥2×10⁻⁶. 8 CFU / mL.

4. The graded aquaculture method according to claim 1, characterized in that, In step S1, the biofilm area is a stacked area of ​​oyster shell fragments piled up along the bottom of the primary mesh, with a width of 8-12 cm and a height of 2-3 cm.

5. The graded aquaculture method according to claim 1, characterized in that, In step S1, the juvenile red swamp crayfish have a body length of 0.8-1.2 cm and are stocked at a density of 800-1200 crayfish / m². 3 ; In step S1, the dosage of Bacillus subtilis agent is 2-3 g / m³. 3 .

6. The graded aquaculture method according to claim 1, characterized in that, Step S1 also includes setting a secondary partition net around the perimeter of the main partition net, which together with the paddy field ridges forms a sub-adult rearing area including a temporary rearing area; after 20-25 days of rearing, the partition net is removed, allowing the shrimp larvae to continue to be reared in the sub-adult rearing area until they reach a body length of 5-6 cm.

7. The graded aquaculture method according to claim 6, characterized in that, Once the shrimp larvae reach a length of 5-6 cm, remove the secondary mesh and allow them to roam freely in the paddy field. Harvest them when they reach a length of 10-12 cm to obtain adult shrimp.

8. The graded aquaculture method according to claim 6, characterized in that, During the sub-adult rearing stage, the feed amount should be 4% to 6% of the total body weight of the shrimp, and the dissolved oxygen level should be maintained at ≥5.5 mg / L.

9. The graded aquaculture method according to claim 1, characterized in that, When raising shrimp in the temporary holding area, the amount of feed should be 6% to 8% of the total body weight of the shrimp, and the dissolved oxygen level should be maintained at ≥6 mg / L. When free-range, the amount of feed should be 3% to 4% of the total body weight of the shrimp, and the dissolved oxygen level should be maintained at ≥5 mg / L.

10. The graded aquaculture method according to claim 8 or 9, characterized in that, Feed 2-3 times a day.

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