Efficient, simple and convenient breeding method for producing two batches of river crabs in one year

Abstract

The invention relates to the technical field of aquaculture, in particular to an efficient and simple breeding technical method capable of producing a batch of all-male tender crabs (river crabs with three shells removed) and a batch of large-size one-year-old juvenile crabs in a river crab breeding pond within one year period, which comprises the following steps: 1, pond selection and transformation, 2, tender crab breeding, and 3, one-year-old juvenile crab breeding. By means of the method, double cultivation in one year and two crabs in one pond are achieved, the single-crop cultivation period is shortened, the cultivation risk is reduced, the pressure of the adult crab market is relieved, the economic benefits of river crab cultivation are greatly improved, and benign development of the industry is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of aquaculture, and in particular to an efficient and convenient breeding technology method capable of producing one batch of all-male juvenile crabs (river crabs that have shed three shells) and one batch of large-sized one-year-old juvenile crabs in a river crab breeding pond within one year. Background Art

[0002] Jiangsu is a major province for river crab farming. In 2022, the total river crab farming area in the province exceeded 4 million mu, and the farming output reached 374,000 tons, accounting for 45.9% of the national total output. At present, most river crab farming is the cultivation of one-year-old crab seeds (deduction crabs) or the cultivation of two-year-old adult crabs. Both models have problems such as high cost (feed, labor), long cycle (one year of farming time), high risk (high temperature weather) and low efficiency (river crabs are concentrated on the market, affecting sales prices). Therefore, how to innovate farming models and technologies and explore new economic growth points is an urgent problem that the river crab industry needs to solve.

[0003] The breeding technology of producing two crops of river crabs within a year refers to the efficient breeding technology that can produce one crop of all-male boy crabs (river crabs that have shed three shells) and one crop of large-sized one-year-old juvenile crabs within a year. This technology can not only meet consumers' demand for early tasting, but also extend the sales cycle of river crabs, reduce breeding risks and improve breeding efficiency. "Boy crabs" refer to the Chinese mitten crabs that can be put on the market in June every year. At this time, the gonads of river crabs are not mature, but the hepatopancreas is clearly visible, and the body weight is 70-160g. It has the characteristics of crispy outer shell, soft inner shell, plump meat and delicious taste. Large-sized one-year-old juvenile crabs generally refer to one-year-old juvenile crabs that have not yet reached sexual maturity and have been cultivated from megalopause to male crabs with individual specifications greater than 15g / piece and female crabs with individual specifications greater than 12g / piece after one year.

[0004] This technology is to release all-male one-year-old juvenile crabs from late December of each year to late February of the following year, and to catch and sell a batch of baby crabs (the first batch) from early June to late July; immediately after the first batch, the pond is cleaned, grass is planted, and "bean crabs" are released, and from late December to late February of the following year, one-year-old buckle crabs (the second batch) are caught and sold. This breeding technology achieves "double breeding in one year, two crabs in one pond", shortens the single-crop breeding cycle, reduces breeding risks, alleviates pressure on the adult crab market, greatly improves the economic benefits of river crab breeding, and is conducive to the healthy development of the industry. Summary of the invention

[0005] The present invention aims at the problems in the background technology, studies the selection and planting of aquatic plants, selection and placement of crab seedlings, selection and precise feeding of bait, water regulation and pre-market nutrition fortification technology in the first batch of boy crab breeding, so as to ensure that the first batch of boy crabs are put on the market early and with high quality; studies the selection and planting of aquatic plants, selection and placement of bean crabs, selection and precise feeding of bait and water regulation technology in the second batch of crab breeding, so as to ensure the production of large-sized one-year-old juvenile crabs.

[0006] In order to achieve the above-mentioned object, the present invention is implemented by the following technical scheme: a method for efficiently breeding two crops of river crabs within a year, the method comprising the following steps:

[0007] 1. Pond selection and renovation

[0008] The pond should be located near the water source and convenient for water inlet and outlet. The pond area should be (5-10)×667㎡, long from east to west and short from north to south, with a length ratio of 2:1-4:1 and a depth of 1.0-1.3m. It should be a flat-bottomed pond or a ring-ditch pond with independent water inlet and outlet, and double-layer slope protection with anti-seepage membrane and mesh. 0.3kw microporous aerator should be installed for every 667㎡, and 2 1.5kw waterwheel-type aerators should be added to each pond at the diagonal position of the pond.

[0009] 2. Crab breeding

[0010] (1) Aquatic plant planting and management

[0011] This technology adopts a simple one-grass-point planting method. From early December to early February each year, only one aquatic grass, Elodea, is used for point planting with a row spacing of 4-5 meters. The diameter of each planting point is preferably 30-50cm. After planting, rooting drugs are sprayed in time. The growth of aquatic grass is relatively slow in the early stage, and it will grow rapidly after mid-March. From May to July, check regularly and control the diameter of each point of aquatic grass to no more than 1.5 meters.

[0012] (2) Selection and placement of crab seedlings

[0013] About 15-20 days after the Elodea is planted, when more than 80% of the Elodea have grown white root hairs, crab seedlings are released. The crab seedlings are selected to be larger than 15g / male crab, and are released in a density of 18-36kg / 667㎡ on a sunny morning.

[0014] (3) Bait selection and precise feeding

[0015] In the early stage, feed with 42%-46% feed protein was used for feeding. About 10 days after the second shell was removed, ice fresh fish + fermented corn were mixed and then fed. The feeding method adopted the point feeding method, that is, when moving along each row of water plants, feed the bait in the middle of every two clusters of water plants, and set up 6-10 bait inspection platforms according to the size of the pond, and regularly check the bait intake to ensure accurate feeding.

[0016] (4) Water regulation

[0017] ① Water level control

[0018] Generally, the water level should be maintained at 30-40cm within 1 month after planting aquatic plants, to ensure that the aquatic plants can carry out good photosynthesis and quickly take root and grow; after the crab seedlings are released, the water level should be maintained at 50-60cm before the end of February to ensure the safe wintering of river crabs and that the aquatic plants can carry out photosynthesis; the precipitation in early March will be down to 40-50cm, so that the water temperature can rise quickly and promote the rapid growth of aquatic plants; from early April to the end of June, the water level will be slowly raised to 70-90cm, so that the aquatic plants have enough growth space, thereby providing a good growth environment for river crabs; from early June to late July, the water level will be lowered to 50-60cm according to market demand to facilitate the catching of baby crabs.

[0019] ②Water quality control

[0020] The whole process is regulated by Special 8 (a composite bacteria). No water adjustment or disinfection drugs are used before mid-March. After mid-March, the pond is disinfected with iodine preparations for the first time. After 2 days of testing, if there is no disinfectant residue, Special 8 composite bacteria is sprayed throughout the pond according to the instructions. After that, half of the Special 8 dosage is sprayed every 15-20 days to regulate the water quality.

[0021] (5) Nutritional fortification before marketing

[0022] In order to ensure high-quality crabs are put on the market, we started feeding them with a mixture of fresh ice fish and fermented corn in a ratio of 2:1-3:1 in early May for nutritional enrichment. About 10 days after the third shell is shed, the water level is lowered to 50-60cm to promote nutrient accumulation.

[0023] (6) Fishing and marketing

[0024] From early June to late July, a batch of crabs are caught and sold according to market conditions. 2-3 days before fishing, the water plants are cleared to force the crabs to accumulate nutrients and facilitate trapping; the water level is lowered to 50-60cm during fishing to facilitate trapping; feeding is stopped on the day of fishing to increase the crabs' activity in finding food and the probability of trapping; oxygenation is stopped at night and the aerator is turned on at 4:00-5:00 in the morning to force the crabs to move around and find oxygen-rich areas and prevent hypoxia in the early morning.

[0025] 3. One-year-old crab farming

[0026] (1) Selection and planting of aquatic plants

[0027] This technology adopts a simple planting method of planting one kind of aquatic plants in a rectangular enclosure. After the crabs are caught, disinfected, cleaned and filled with water, a 6-10m x 2-3m rectangular enclosure is set up in the pond along the east-west direction, with a vertical spacing of 1-2m and a horizontal spacing of 2-3m (seeFigure 1 The rectangular enclosure is fixed with wooden sticks or steel pipes inserted into the bottom mud. Then a rectangular PVC pipe floating enclosure slightly larger than the fixed rod is placed outside the fixed rod. A mesh with a mesh size of 6-8 cm is set up inside the enclosure (see Figure 2 ). Only one type of waterweed, water peanut, was selected and placed on the mesh inside the rectangular enclosure.

[0028] (2) Selection and distribution of bean crabs

[0029] At night, ground traps are placed in the crab breeding pond until the next morning to catch crabs. Bean crabs with an average size of about 1g per crab (0.8g / crab to 1.2g / crab is appropriate) are selected and released at a rate of 30-40kg / 667㎡. The release is completed before the sun comes out. Anti-stress drugs are sprayed throughout the pond 1 hour before release and micropore oxygenation is turned on.

[0030] (3) Bait selection and precise feeding

[0031] In the first month, fresh ice fish + 42%-46% feed protein compound feed were mixed and fed. After one month, only 42%-46% feed protein compound feed was fed. In early December, fresh ice fish were fed. The feeding method adopted the point feeding method, that is, feeding the bait in the middle of every two enclosures along the longitudinal direction, and 6-10 bait inspection platforms were set up according to the size of the pond, and the bait intake was checked regularly to ensure accurate feeding.

[0032] (4) Water regulation technology

[0033] ① Water level control

[0034] Generally, the water level should be maintained at 60-100cm during the high temperature period after the water peanuts are placed on the net to ensure that the young crabs can safely survive the high summer temperatures; after late September, as the temperature drops, the water level can be appropriately lowered to 50-100cm; the water level should be lowered to below 50cm one week before fishing to facilitate fishing in ground traps.

[0035] ②Water quality control

[0036] The whole process is regulated by Te 8 (a composite bacteria), without any water adjustment or disinfection drugs. After the crab pond is cleaned, the pond is disinfected with quicklime for the first time. After 2 days of testing, if there is no disinfectant residue, Te 8 composite bacteria is sprayed throughout the pond according to the instructions. After that, half of the Te 8 dosage is sprayed every 15-20 days to regulate the water quality.

[0037] (5) Fishing and marketing

[0038] From late December to late February of the following year, the second batch of one-year-old crabs are caught and sold according to market conditions. When fishing, the water level is lowered to 40-50cm to facilitate entry into the cages. In the later stage, when the number of crabs entering the cages is too small, the pond is dried up for fishing.

[0039] The breeding technology of the present invention realizes "double breeding in one year, two crabs in one pond", shortens the single-crop breeding cycle, reduces breeding risks, alleviates the pressure on the adult crab market, greatly improves the economic benefits of river crab breeding, and is conducive to the healthy development of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described below with reference to the accompanying drawings:

[0041] Figure 1 Schematic diagram of the rectangular grid layout of water plants in the pond;

[0042] Figure 2 This is a top view of the rectangular grid of water plants in the pond; DETAILED DESCRIPTION

[0043] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0044] Any feature disclosed in this specification (including any additional claims and abstract), unless otherwise stated, may be replaced by other equivalent or alternative features having similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0045] Example:

[0046] A method for efficiently breeding two crops of river crabs within a year, the method comprising the following steps:

[0047] 1. Pond selection and renovation

[0048] The pond should be located near the water source and convenient for water inlet and outlet. The pond area should be (5-10)×667㎡, long from east to west and short from north to south, with a length ratio of 2:1-4:1 and a depth of 1.0-1.3m. It should be a flat-bottomed pond or a ring-ditch pond with independent water inlet and outlet, and double-layer slope protection with anti-seepage membrane and mesh. 0.3kw microporous aerator should be installed for every 667㎡, and 2 1.5kw waterwheel-type aerators should be added to each pond at the diagonal position of the pond.

[0049] 2. Crab breeding

[0050] (1) Aquatic plant planting and management

[0051] This technology adopts a simple one-grass-point planting method. From early December to early February each year, only one aquatic grass, Elodea, is used for point planting with a row spacing of 4-5 meters. The diameter of each planting point is preferably 30-50cm. After planting, rooting drugs are sprayed in time. The growth of aquatic grass is relatively slow in the early stage, and it will grow rapidly after mid-March. From May to July, check regularly and control the diameter of each point of aquatic grass to no more than 1.5 meters.

[0052] (2) Selection and placement of crab seedlings

[0053] About 15-20 days after the Elodea is planted, when more than 80% of the Elodea have grown white root hairs, crab seedlings are released. The crab seedlings are selected to be larger than 15g / male crab, and are released in a density of 18-36kg / 667㎡ on a sunny morning.

[0054] (3) Bait selection and precise feeding

[0055] In the early stage, feed with 42%-46% feed protein was used for feeding. About 10 days after the second shell was removed, ice fresh fish + fermented corn were mixed and then fed. The feeding method adopted the point feeding method, that is, when moving along each row of water plants, feed the bait in the middle of every two clusters of water plants, and set up 6-10 bait inspection platforms according to the size of the pond, and regularly check the bait intake to ensure accurate feeding.

[0056] (4) Water regulation

[0057] ① Water level control

[0058] Generally, the water level should be maintained at 30-40cm within 1 month after planting aquatic plants, to ensure that the aquatic plants can carry out good photosynthesis and quickly take root and grow; after the crab seedlings are released, the water level should be maintained at 50-60cm before the end of February to ensure the safe wintering of river crabs and that the aquatic plants can carry out photosynthesis; the precipitation in early March will be down to 40-50cm, so that the water temperature can rise quickly and promote the rapid growth of aquatic plants; from early April to the end of June, the water level will be slowly raised to 70-90cm, so that the aquatic plants have enough growth space, thereby providing a good growth environment for river crabs; from early June to late July, the water level will be lowered to 50-60cm according to market demand to facilitate the catching of baby crabs.

[0059] ②Water quality control

[0060] The whole process is regulated by Special 8 (a composite bacteria). No water adjustment or disinfection drugs are used before mid-March. After mid-March, the pond is disinfected with iodine preparations for the first time. After 2 days of testing, if there is no disinfectant residue, Special 8 composite bacteria is sprayed throughout the pond according to the instructions. After that, half of the Special 8 dosage is sprayed every 15-20 days to regulate the water quality.

[0061] (5) Nutritional fortification before marketing

[0062] In order to ensure high-quality crabs are put on the market, we started feeding them with a mixture of fresh ice fish and fermented corn in a ratio of 2:1-3:1 in early May for nutritional enrichment. About 10 days after the third shell is shed, the water level is lowered to 50-60cm to promote nutrient accumulation.

[0063] (6) Fishing and marketing

[0064] From early June to late July, a batch of crabs are caught and sold according to market conditions. 2-3 days before fishing, the water plants are cleared to force the crabs to accumulate nutrients and facilitate trapping; the water level is lowered to 50-60cm during fishing to facilitate trapping; feeding is stopped on the day of fishing to increase the crabs' activity in finding food and the probability of trapping; oxygenation is stopped at night and the aerator is turned on at 4:00-5:00 in the morning to force the crabs to move around and find oxygen-rich areas and prevent hypoxia in the early morning.

[0065] 3. One-year-old crab farming

[0066] (1) Selection and planting of aquatic plants

[0067] This technology adopts a simple planting method of planting one kind of aquatic plants in a rectangular enclosure. After the crabs are caught, disinfected, cleaned and filled with water, a 6-10m x 2-3m rectangular enclosure is set up in the pond along the east-west direction, with a vertical spacing of 1-2m and a horizontal spacing of 2-3m (see Figure 1 The rectangular enclosure is fixed with wooden sticks or steel pipes inserted into the bottom mud. Then a rectangular PVC pipe floating enclosure slightly larger than the fixed rod is placed outside the fixed rod. A mesh with a mesh size of 6-8 cm is set up inside the enclosure (see Figure 2 ). Only one type of waterweed, water peanut, was selected and placed on the mesh inside the rectangular enclosure.

[0068] (2) Selection and distribution of bean crabs

[0069] At night, ground traps are placed in the crab breeding pond until the next morning to catch crabs. Bean crabs with an average size of about 1g per crab (0.8g / crab to 1.2g / crab is appropriate) are selected and released at a rate of 30-40kg / 667㎡. The release is completed before the sun comes out. Anti-stress drugs are sprayed throughout the pond 1 hour before release and micropore oxygenation is turned on.

[0070] (3) Bait selection and precise feeding

[0071] In the first month, fresh ice fish + 42%-46% feed protein compound feed were mixed and fed. After one month, only 42%-46% feed protein compound feed was fed. In early December, fresh ice fish were fed. The feeding method adopted the point feeding method, that is, feeding the bait in the middle of every two enclosures along the longitudinal direction, and 6-10 bait inspection platforms were set up according to the size of the pond, and the bait intake was checked regularly to ensure accurate feeding.

[0072] (4) Water regulation technology

[0073] ① Water level control

[0074] Generally, the water level should be maintained at 60-100cm during the high temperature period after the water peanuts are placed on the net to ensure that the young crabs can safely survive the high summer temperatures; after late September, as the temperature drops, the water level can be appropriately lowered to 50-100cm; the water level should be lowered to below 50cm one week before fishing to facilitate fishing in ground traps.

[0075] ②Water quality control

[0076] The whole process is regulated by Te 8 (a composite bacteria), without any water adjustment or disinfection drugs. After the crab pond is cleaned, the pond is disinfected with quicklime for the first time. After 2 days of testing, if there is no disinfectant residue, Te 8 composite bacteria is sprayed throughout the pond according to the instructions. After that, half of the Te 8 dosage is sprayed every 15-20 days to regulate the water quality.

[0077] (5) Fishing and marketing

[0078] From late December to late February of the following year, the second batch of one-year-old crabs are caught and sold according to market conditions. When fishing, the water level is lowered to 40-50cm to facilitate entry into the cages. In the later stage, when the number of crabs entering the cages is too small, the pond is dried up for fishing.

[0079] Table 1 below shows data related to the production and benefits of river crabs cultured using the present invention.

[0080] Table 1. River crab production and benefits

[0081]

[0082]

[0083] The basic teachings of the present invention have been described, and many extensions and variations will be apparent to those having ordinary skill in the art. Since the invention disclosed in the specification may be implemented in other specific forms without departing from the spirit or general characteristics of the invention, and some of these specific forms have been pointed out, the embodiments disclosed in the specification should be regarded as illustrative rather than limiting. The scope of the present invention is defined by the appended claims, rather than by the above description, and all changes in the equivalent meaning and scope that fall within the claims are still included within their scope.

Claims

1. A method for efficiently breeding river crabs to produce two crops per year. It is characterized in that The method comprises the following steps:

1. Pond selection and renovation The pond should be located near the water source and convenient for water inlet and outlet. The pond area should be (5-10)×667㎡, long from east to west and short from north to south, with a length ratio of 2:1-4:1 and a depth of 1.0-1.3m. It should be a flat-bottomed pond or a ring-ditch pond with independent water inlet and outlet, and double-layer slope protection with anti-seepage membrane and mesh. 0.3kw microporous aerator should be installed for every 667㎡, and 2 1.5kw waterwheel-type aerators should be added to each pond at the diagonal position of the pond.

2. Crab breeding (1) Aquatic plant planting and management Use a simple one-grass-point planting method; from early December to early February each year, only one aquatic grass, Elodea, is used for point planting with a row spacing of 4-5 meters. The diameter of each planting point should be 30-50cm. After planting, spray the rooting-promoting drugs in time; the growth of aquatic grass is relatively slow in the early stage, and it will grow rapidly after mid-March. Check regularly from May to July and control the diameter of each aquatic grass point to no more than 1.5 meters; (2) Selection and placement of crab seedlings About 15-20 days after the Elodea is planted, when more than 80% of the Elodea have grown white root hairs, crab seedlings are released; the crab seedlings are selected to be larger than 15g / male crab, and are released in the morning on sunny days at a density of 18-36kg / 667㎡; (3) Bait selection and precise feeding In the early stage, feed with 42%-46% protein was used for feeding. About 10 days after the second shell was shed, ice-fresh fish + fermented corn were mixed and then fed. The feeding method adopted the point feeding method, that is, when moving along each row of water plants, feed the bait in the middle of every two clusters of water plants, and set up 6-10 bait inspection platforms according to the size of the pond, and regularly check the bait intake to ensure accurate feeding. (4) Water regulation ① Water level control Generally, the water level should be maintained at 30-40cm within one month after the planting of aquatic plants, to ensure that the aquatic plants can photosynthesize well and take root quickly; after the crab seedlings are released, the water level should be maintained at 50-60cm before the end of February to ensure that the river crabs can safely overwinter and that the aquatic plants can photosynthesize; the precipitation in early March will be 40-50cm, so that the water temperature can rise quickly and promote the rapid growth of aquatic plants; from early April to the end of June, the water level will be slowly raised to 70-90cm, so that the aquatic plants have enough growth space, thereby providing a good growth environment for river crabs; from early June to late July, the water level will be lowered to 50-60cm according to market demand to facilitate the fishing of baby crabs; ②Water quality control The whole process is regulated by Special 8 (a composite bacteria); no water adjustment and disinfection drugs are used before mid-March; after mid-March, the whole pond is disinfected with iodine preparations for the first time. After 2 days of testing, if there is no disinfectant residue, the Special 8 composite bacteria is sprayed throughout the pond according to the instructions. After that, half of the Special 8 usage is sprayed every 15-20 days for water quality control; (5) Nutritional fortification before marketing In order to ensure high-quality crabs are put on the market, we started to feed them with fresh fish and fermented corn in a ratio of 2:1-3:1 in early May for nutritional enhancement. About 10 days after the third shell is shed, the water level is lowered to 50-60cm to promote nutrient accumulation; (6) Fishing and marketing From early June to late July, a batch of crabs are caught and sold according to market conditions. 2-3 days before fishing, the aquatic plants are removed to force the crabs to accumulate nutrients and facilitate trapping. When fishing, the water level is lowered to 50-60cm to facilitate trapping. Feeding is stopped on the day of fishing to increase the crabs' activity in finding food and the probability of trapping. Oxygenation is stopped at night and the aerator is turned on at 4:00-5:00 in the morning to force the crabs to move around in oxygen-rich areas and prevent hypoxia in the early morning.

3. One-year-old crab farming (1) Selection and planting of aquatic plants A simple planting method of planting one kind of aquatic grass in a rectangular enclosure is adopted; after the crabs are caught, disinfected, cleaned and filled with water, a 6-10m×2-3m rectangular enclosure is set up in the pond along the east-west direction, with a longitudinal enclosure spacing of 1-2m and a lateral spacing of 2-3m; wooden sticks or steel pipes are inserted into the bottom mud to fix the rectangular enclosure, and then a rectangular PVC pipe floating enclosure slightly larger than the fixed rod is placed outside the fixed rod, and a mesh with a mesh size of 6-8cm is set up in the enclosure; only one kind of aquatic grass, water peanut, is selected and placed on the mesh in the rectangular enclosure; (2) Selection and distribution of bean crabs At night, place ground traps in the crab breeding pond and catch them at dawn the next day. Select crabs with an average size of about 1g / piece (0.8g / piece to 1.2g / piece is appropriate). Stock them at a rate of 30-40kg / 667㎡. Stocking is completed before the sun comes out. Spray anti-stress drugs throughout the pond 1 hour before stocking, and open microporous aeration. (3) Bait selection and precise feeding In the first month, fresh-frozen fish + 42%-46% feed protein compound feed were mixed and fed. After one month, only 42%-46% feed protein compound feed was fed. In early December, fresh-frozen fish were fed. The feeding method adopted was point feeding, that is, the bait was fed in the empty space between every two enclosures along the longitudinal direction, and 6-10 bait inspection platforms were set up according to the size of the pond. The bait intake was checked regularly to ensure accurate feeding. (4) Water regulation technology ① Water level control Generally, the water level should be kept at 60-100cm during the high temperature period after the crabs are placed on the net to ensure that the crabs can safely survive the high temperature in summer. After late September, as the temperature drops, the water level can be appropriately lowered to 50-100cm. The water level should be lowered to below 50cm one week before fishing to facilitate trap fishing. ②Water quality control The whole process is regulated by Special 8 (a composite bacteria), without any water adjustment or disinfection drugs. After the crab pond is cleaned, the pond is disinfected with quicklime for the first time. After 2 days, if there is no disinfectant residue, the Special 8 composite bacteria is sprayed in the whole pond according to the instructions. After that, half of the Special 8 dosage is sprayed every 15-20 days to regulate the water quality. (5) Fishing and marketing From late December to late February of the following year, the second batch of one-year-old crabs are caught and sold according to market conditions. When fishing, the water level is lowered to 40-50cm to facilitate entry into the cages. In the later stage, if the number of crabs entering the cages is too small, the pond is dried up for fishing.

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