Method for cultivating mandarin fish by net enclosure in river crab intensive breeding pond

Abstract

The present invention relates to the technical field of aquaculture production, and in particular to a method for culturing mandarin fish in a river crab intensive breeding pond. The method comprises setting a gabion fence net in the river crab intensive breeding pond; the area of ​​the gabion fence net accounts for 5-8% of the area of ​​the river crab intensive breeding pond; mandarin fish is cultured in the gabion fence net; the gabion fence net comprises a gabion net, a fishing net fence and a plastic escape prevention board; the gabion net is located at the bottom of the fishing net fence; the plastic escape prevention board is located at the top of the fishing net fence. The present invention greatly increases the amount of mandarin fish released compared to the mandarin fish culture mode in the river crab pond, reduces the disease incidence rate compared to the single-species intensive breeding mode of mandarin fish in the pond, has a higher cultivation rate, and has more uniform specifications of adult mandarin fish, a higher sales price, and significant economic benefits by culturing mandarin fish in high-density cages (gabion fence nets).

Description

Technical Field

[0001] The invention relates to the technical field of aquaculture production, in particular to a method for cultivating mandarin fish by net enclosure in a river crab intensive breeding pond. Background Art

[0002] River crabs, scientifically known as Chinese mitten crabs (Eriocheir sinensis), are important high-quality aquatic products. With the increase in river crab farming area and the improvement of farming technology, the yield per unit area has continued to increase, but the farming cost has risen and the sales market has become saturated. The industry competition has become increasingly fierce, and the profit margin has become increasingly narrow. Optimizing and improving the existing farming model is an urgent requirement for the industry's continued high-quality development.

[0003] Mandarin fish (Siniperca chuatsi) has tender meat, delicious taste, and few intramuscular bones. It is a precious fish favored by people. With the improvement of residents' living standards, the market demand for mandarin fish has increased year by year, but the current aquaculture industry is difficult to expand, mainly due to the following two reasons: first, the natural biological habits of mandarin fish require feeding on live bait fish, which is costly, technically difficult and labor-intensive to feed; second, the aquaculture water under the high-density intensive breeding model often has low dissolved oxygen, and high concentrations of ammonia nitrogen and nitrite, which makes mandarin fish prone to diseases such as iridovirus disease under environmental stress. The disease is difficult to prevent and treat and has a high mortality rate after an outbreak.

[0004] The abundant aquatic plants and sufficient dissolved oxygen in the river crab breeding pond are also very suitable for breeding mandarin fish. First, mandarin fish can eat wild fish in the pond as live bait, converting wild fish with low economic value into mandarin fish with high economic value; second, the excrement produced by mandarin fish during its growth can be used as biological fertilizer in the river crab pond, for the use of aquatic plants to re-enter the pond ecological chain cycle, which can not only reduce the additional application of fertilizers to the river crab pond, but also avoid the high concentration of ammonia nitrogen and nitrite caused by high-density breeding of mandarin fish. Diseases can also be reduced, and the discharge of breeding tail water can be reduced. At present, it is a relatively mature technology to breed mandarin fish in river crab intensive breeding ponds and is favored by farmers in practice. However, the specifications of mandarin fish raised under low-density breeding are often different after being raised, and the amount of mandarin fish released under the breeding model is limited, generally with a stocking density of 10-15 per mu, so the economic increment is also limited. When there are few wild fish in the river crab breeding pond, the yield and survival rate are lower, and the yield of mandarin fish breeding is not guaranteed. Summary of the invention

[0005] Based on the above content, the present invention provides a method for cultivating mandarin fish in a river crab intensive breeding pond. The present invention realizes high-density breeding of mandarin fish by setting a stone cage fence in the river crab intensive breeding pond, and fully utilizes the high-quality water environment in the river crab breeding pond without affecting the output and specifications of river crab breeding, and harvests large-sized and high-quality mandarin fish, which not only ensures the output and benefits of river crabs, but also greatly improves the total output value and total economic benefits of the pond through the increase in the production of mandarin fish.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for culturing mandarin fish in a river crab intensive breeding pond, comprising the following steps: setting a gabion fence net in the river crab intensive breeding pond; the area of ​​the gabion fence net accounts for 5-8% of the area of ​​the river crab intensive breeding pond; culturing mandarin fish in the gabion fence net;

[0008] The gabion fence comprises a gabion net, a fishing net fence and a plastic anti-escape plate; the gabion net is located at the bottom of the fishing net fence; and the plastic anti-escape plate is located at the top of the fishing net fence.

[0009] In a preferred embodiment of the present invention, the gabion fence is located near the bank of the river crab intensive breeding pond; the gabion fence is buried 15-20 cm from the bottom of the river crab intensive breeding pond; the fishing net fence is 30-50 cm above the highest water level during the breeding process; the plastic escape prevention board is located 20-30 cm from the top of the fishing net fence; and the gabion fence is circular.

[0010] In a preferred embodiment of the present invention, the following steps are included:

[0011] (1) Renovation of breeding ponds: including setting up circular net enclosures in intensive crab breeding ponds;

[0012] (2) Preparation before aquaculture: including pond cleaning, disinfection, pond drying, fertilization and planting of aquatic plants;

[0013] (3) River crab farming: including river crab selection and release;

[0014] (4) Stocking of mandarin fish fry: including the selection and stocking of mandarin fish fry;

[0015] (5) Feeding: including feed selection, feeding time, feeding location and feeding amount;

[0016] (6) Aquatic plant management: including aquatic plant species, aquatic plant cutting and combing;

[0017] (7) Water quality management: including water quality, water level, water temperature and water color;

[0018] (8) River crab fishing: including fishing time and fishing methods;

[0019] (9) Fishing nets for mandarin fish: including fishing time and fishing methods.

[0020] In a preferred embodiment of the present invention, the river crab intensive breeding pond is long from east to west and narrow from north to south, and is rectangular with arc-shaped corners; the pond bank is 2-3m wide, with a slope ratio of 1:2-3, a pond depth of 1.5-1.8m, and an area of ​​10-20 mu; water inlet gates and drainage gates are set at both ends of the river crab intensive breeding pond, and a mesh of 0.6-0.8cm mesh is set outside the water inlet.

[0021] In a preferred embodiment of the present invention, the stocking density of the river crabs is 1000-1500 crabs / mu, and the specification is 80-120 crabs / kg.

[0022] In a preferred embodiment of the present invention, the mandarin fish are selected from healthy, well-tamed mandarin fish fry that eat granular feed, 15-30 fish / jin, and 8,000-10,000 mandarin fish fry are released per mu; the mandarin fish fry are released in early June.

[0023] In a preferred embodiment of the present invention, during the culture process of river crabs, they are fed once a day, at 4-5 pm. During the high temperature period in summer and autumn, they are fed for two consecutive days and then stopped for one day. The feeding amount is 6-10% of the body weight of the river crabs. During the culture process of mandarin fish, they are fed twice a day, at 6-7 am and 5-6 pm, and the feeding amount is 3% of the pond stock of mandarin fish.

[0024] In a preferred embodiment of the present invention, the water depth in the intensive crab breeding pond is controlled at 0.5-0.6m in spring and maintained at 1.2-1.5m in summer and autumn, the dissolved oxygen in the water is not less than 5mg / L, and the pH value of the water is maintained at 7-9.

[0025] In a preferred embodiment of the present invention, the river crab fishing time is from mid-October to mid-to-early November, using a combination of hand-catching and ground trap crab catching; the mandarin fish fishing time is from late November to December, using a dragnet fishing method.

[0026] The second technical solution of the present invention is a method for increasing the density of mandarin fish cultured in a river crab intensive culture pond, which adopts the above-mentioned method of culturing mandarin fish in a net enclosure in a river crab intensive culture pond.

[0027] The present invention discloses the following technical effects:

[0028] (1) Significant economic benefits

[0029] Convenient breeding management: Mandarin fish usually live on the bottom and gather in groups when feeding. When living on the bottom, the water in the pond is prone to turbidity, which affects the photosynthesis of the pond water. After the mandarin fish are raised in nets, the transparency of the water in most areas increases, photosynthesis is enhanced, and it is more conducive to the growth of other aquatic organisms such as river crabs.

[0030] Uniform specifications of adult fish: The invention makes the specifications of adult fish grown by mandarin fish in high-density cage culture more uniform than those grown in sparse pond culture mode, and the selling price is higher.

[0031] High breeding success rate: Mandarin fish cultured in conventional ponds suffers from serious diseases and has a low breeding success rate. Disease is an important factor hindering the development of mandarin fish farming. There is no mutual infection of diseases between river crabs and mandarin fish. The average per-acre breeding density of mandarin fish cultured in fences in river crab breeding ponds is low, less than 1 / 5 of that in conventional intensive breeding ponds. The good ecological environment of river crab ponds can reduce the occurrence of mandarin fish diseases and greatly improve the success rate of mandarin fish farming.

[0032] The sales profit is considerable: Mandarin fish are cultured in fences in river crab ponds, and the average stocking quantity per mu in the whole pond can reach 600-700. The breeding cost is calculated as 22 yuan / jin by feeding high-protein compound feed throughout the whole process. The selling price of adult mandarin fish is 30-60 yuan / jin. The yield per mu of mandarin fish is 650-800 jin, and the profit is more than 8 yuan / jin. Without affecting the profit of crabs, the average income per mu can be increased by more than 5,000 yuan, with significant economic benefits.

[0033] (2) Obvious ecological benefits

[0034] Fewer diseases of mandarin fish: The use of drugs for disease prevention and treatment is reduced accordingly, reducing the pollution of water bodies caused by the use of drugs.

[0035] Aquaculture ecological complementarity: The nitrogen, phosphorus, potassium and other nutrients in the excrement of mandarin fish can be absorbed by aquatic plants and algae and re-enter the pond ecological chain, reducing the application of fertilizers. At the same time, the mandarin fish aquaculture tail water is purified by the pond itself, reducing the discharge of aquaculture tail water.

[0036] (3) Highly replicable and scalable

[0037] Adding nets to crab ponds to culture mandarin fish is a simple transformation with low investment cost, low technical requirements, strong operability, and the ability to adapt to ponds of different sizes, making it easily accepted by fishermen. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 The present invention is a schematic diagram of a gabion fence; in the figure, 1 is a gabion fence, 2 is a fishing net fence, and 3 is a plastic escape prevention board. DETAILED DESCRIPTION

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0044] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0045] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0046] The first aspect of the present invention provides a method for culturing mandarin fish in a river crab intensive culture pond, comprising the following steps: setting a gabion fence net in the river crab intensive culture pond; the area of ​​the gabion fence net accounts for 5-8% of the area of ​​the river crab intensive culture pond; culturing mandarin fish in the gabion fence net;

[0047] If the area of ​​gabion fence accounts for less than 5% of the area of ​​intensive river crab pond, the amount of mandarin fish released is small and the economic benefits are reduced. If it accounts for more than 8%, the fish excrement and remaining feed not eaten by fish produced by mandarin fish farming are too much, which exceeds the self-purification capacity of the river crab pond ecology, damages the pond ecology and ultimately affects the production and economic benefits of river crabs and mandarin fish.

[0048] The gabion fence comprises a gabion net, a fishing net fence and a plastic anti-escape plate; the gabion net is located at the bottom of the fishing net fence; and the plastic anti-escape plate is located at the top of the fishing net fence.

[0049] In a preferred embodiment of the present invention, the gabion fence is located near the bank of the river crab intensive breeding pond (the purpose of setting it near the bank is to facilitate the breeding and management of mandarin fish, because the nearshore is convenient for the release of fry, feeding and other daily manual management; the river crab intensive breeding pond in the present invention is rectangular with four arc-shaped corners, and the gabion fence is located in the southwest corner of the river crab intensive breeding pond); the gabion net is buried 15-20 cm from the bottom of the river crab intensive breeding pond; the fishing net fence is 30-50 cm higher than the highest water level during the breeding process; the plastic escape prevention board is located 20-30 cm from the top of the fishing net fence; the gabion fence is circular.

[0050] In a preferred embodiment of the present invention, the following steps are included:

[0051] (1) Renovation of breeding ponds: including setting up circular net enclosures in intensive crab breeding ponds;

[0052] (2) Preparation before aquaculture: including pond cleaning, disinfection, pond drying, fertilization and planting of aquatic plants;

[0053] (3) River crab farming: including river crab selection and release;

[0054] (4) Stocking of mandarin fish fry: including the selection and stocking of mandarin fish fry;

[0055] (5) Feeding: including feed selection, feeding time, feeding location and feeding amount;

[0056] (6) Aquatic plant management: including aquatic plant species, aquatic plant cutting and combing;

[0057] (7) Water quality management: including water quality, water level, water temperature and water color;

[0058] (8) River crab fishing: including fishing time and fishing methods;

[0059] (9) Fishing nets for mandarin fish: including fishing time and fishing methods.

[0060] In a preferred embodiment of the present invention, in step (1), the river crab intensive breeding pond is preferably long from east to west and narrow from north to south; it is rectangular with arc-shaped corners; the pond bank is 2-3m wide with a slope ratio of 1:2-3, and must be compacted to prevent water leakage and water seepage. The river crab intensive breeding pond is preferably 1.5-1.8m deep and 10-20 mu in area. A high-inlet and low-drainage system is set up, and a water inlet gate and a water outlet gate are set at both ends of the river crab intensive breeding pond. A mesh sheet with a mesh size of 0.6-0.8cm is set outside the water inlet to prevent debris from entering the river crab intensive breeding pond. A 40-mesh dense water filter bag is set at the water inlet to prevent eggs and seedlings of wild fish and other enemies from entering the crab pond with the water flow; a net cage is set at the drain outlet to prevent river crabs from escaping with the water. A 65cm high escape-proof membrane is used to build an escape-proof wall around the pond, and the lower end of the escape-proof membrane is inserted into the soil for no less than 15cm, and the escape-proof membrane is fixed with a bamboo pole. The bamboo pole is inserted on the outside of the escape-proof membrane. Select an appropriate location near the pond bank and set up a circular net enclosure (gabion fence net). The circular area is 5%-8% of the pond area. The bottom of the net enclosure is buried 15cm-20cm deep in the bottom of the pond with a gabion net (gabion net is made of No. 6 fish net into a long bag shape, filled with stones in the middle, and the diameter is more than 8cm). The upper part of the gabion net is sewn with a fishing net (fishing net fence). The mesh side length is about 1cm. The fishing net is supported by pipes 30cm above the highest water level during the breeding process. A 20cm high plastic escape prevention board is set on the outside of the top of the fishing net to prevent river crabs from entering the mandarin fish breeding area; prevent river crabs and mandarin fish from escaping from each other. An oxygenation device is set in the net enclosure, with aeration plates set around and an impeller aerator in the middle.

[0061] In step (2), the above-mentioned preparation for breeding is carried out when the pond is idle in winter. First, the pond water is drained, the pond is sun-dried, disinfected, and the pond is cleaned. Then, fertilization is carried out and the central field is rotary-tilled and exposed to the sun for about one month. After 7-10 days of pond cleaning, new water is injected into the surrounding ditch to control the water level at 30-40 cm.

[0062] In step (3), the stocking of river crabs is carried out in mid-to-late January after the gabion fence is set up. River crabs are released into the breeding pond and the outer area of ​​the gabion fence net, with a density of 1000-1500 crabs / mu and a specification of 80-120 crabs / kg. The water level should not be too deep during stocking, and should be maintained at about 50-60cm, which is conducive to absorbing solar heat to increase the water temperature and promote the early feeding and early growth of river crabs. The water temperature should be maintained at about 10°C during stocking. If the water temperature is too low, the river crabs are susceptible to frostbite. If the water temperature is too high, it is not conducive to the fishing, transportation, and stocking of river crabs, and they are susceptible to diseases and insect pests.

[0063] In step (4), the mandarin fish fry are released in early June. Healthy mandarin fish fry that have been acclimated and fed with granular feed are selected, 15-30 fry / jin, and 8000-10000 fry are released per mu.

[0064] In step (5), the feed is generally mainly granular feed, supplemented by animal bait, so that the crabs are "fine at both ends and green in the middle". During the breeding process, the crabs are generally fed once a day at 4-5 pm. In the high temperature period of summer and autumn, they are fed for two consecutive days and then stopped for one day. The feeding amount is 6-10% of the crab's body weight. It is better to observe the feeding situation using a net-shaped feeding table made of plastic woven bags or dense mesh.

[0065] The feed for mandarin fish should be high-quality and palatable special mandarin fish feed, and it should be fed twice a day, in the morning before 7 o'clock in the morning and in the afternoon from 5 o'clock to dark. Check the feeding situation every day, control the total amount of feeding, and do not feed too much. According to the season, weather, water quality and feeding situation, feed more on sunny days and when the feeding is strong; feed less on cloudy days and when the water temperature is low; do not feed on rainy days.

[0066] In step (6), the aquatic weed management is to start planting aquatic weeds 7-10 days after the pond is cleared in winter. The aquatic weeds are elodea or hydrilla verticillata. The aquatic weed planting area is outside the gabion fence net, and no planting is done inside the fence net. After the aquatic weeds grow normally, river crabs are put in. When patrolling the pond every day, pay attention to the growth of aquatic weeds, fertilize or cut off the aquatic weeds in an aging state to keep the aquatic weeds fresh and tender. Ponds with poor growth of aquatic weeds should be properly fertilized in the aquatic weed area, and areas with insufficient aquatic weeds should be replanted or transplanted in time, so as to strive to make the aquatic weeds in the pond sparse and dense and reasonably laid out. The aquatic weed area is maintained between 50% and 60% of the entire water surface. When the pond is closed due to excessive aquatic weeds, several waterways in the north-south direction should be opened to facilitate the smooth flow of water in the pond, maintain a good ecological environment in the pond, and facilitate feeding and management.

[0067] The water quality management described in step (7) refers to the different requirements of the crab pond for the water level in different seasons. In spring, in order to increase the water temperature and promote the growth of river crabs, the water level can be controlled at 0.5-0.6m. In summer and autumn, the water temperature is higher and the depth of the pond water should be maintained at 1.2-1.5m. The water quality should be kept fresh throughout the whole process, the aerator should be turned on frequently, the dissolved oxygen should be kept sufficient, and the dissolved oxygen in the pond water should be maintained above 5mg / L. The pH value of the pond water should be maintained at 7-9, and the optimum is 7.5-8.5. The water should be changed once a week in spring and once every 3 days in summer. In case of continuous high temperature, the water should be changed every day. In autumn, when the weather is hot, the water should be changed every 2 days, and the amount of water changed should account for 1 / 3 of the entire water area.

[0068] In step (8), the river crab fishing is carried out from mid-October to November. The method is a combination of hand-catching and ground crab trapping. During the fishing period, the water level of the pond is appropriately lowered, and the river crabs are used to go ashore at night to forage for food. Ground traps are arranged around, manpower is organized, and flashlights and crab baskets are prepared to catch the crabs.

[0069] In step (9), the mandarin fish is caught after the crab is caught, in late November to December, by drag net fishing and then catching in a dry pond. At this time, the mandarin fish has basically reached the commercial fish specification of 450g-700g / tail. The mandarin fish can also be moved to other breeding ponds for temporary breeding and sale.

[0070] The second aspect of the present invention provides a method for increasing the density of mandarin fish cultured in a river crab intensive culture pond, using the above-mentioned method for culture mandarin fish in a river crab intensive culture pond using a net.

[0071] Unless otherwise specified, the raw materials used in the embodiments of the present invention can be obtained through commercial sources.

[0072] The granular protein feed used in the embodiment of the present invention was purchased from Changzhou Haida Biological Feed Co., Ltd. The feed parameters were: moisture ≤ 10%, crude protein ≥ 49%, crude fiber ≤ 3%, crude fat ≥ 5%, total phosphorus ≥ 1.2%, lysine ≥ 3%; the corn was cooked before feeding.

[0073] The present invention will be further described below by way of examples.

[0074] Example 1

[0075] (1) Pond conditions: The river crab breeding pond is east-west oriented and covers an area of ​​15 mu. The embankment around the breeding pond is 1.8m higher than the bottom of the surrounding ditch, the top width of the embankment is 2.0m, and the slope ratio of the embankment is 1:2.5.

[0076] (2) Preparation before breeding: In winter, drain the pond water, clean the pond, disinfect and dry the pond first, then apply fertilizer, set up escape prevention walls and plant Elodea (the planting area is outside the gabion fence, and no planting is done inside the fence. River crabs will be put in after the aquatic plants grow normally). 1.2 acres are enclosed in the southwest corner of the pond to set up a gabion fence. The gabion is buried 15 cm from the bottom of the pond. The fishing net fence is 1.8 m high. A plastic escape prevention board is placed 20 cm from the top of the fishing net fence. An impeller aerator is installed in the center of the fence. Four aeration plates are evenly set up near the fishing net (0.5-0.6 m above the bottom of the pond).

[0077] (3) Stocking crabs: After the growth of aquatic plants (Elodea) is stable, continue to inject new water, the water level is 50-60cm, and the water temperature is maintained at around 10℃. In late January, stock crabs at a rate of 1,500 per mu, with a size of 80-120 per kg.

[0078] (4) Release of Mandarin Fish Fry: In early June, purchase Mandarin Fish Fry (30 fish / catties) that have been acclimated to feed on pellet feed. 2 A total of 10,000 fish were placed in the gabion fence.

[0079] (5) Feeding: The crabs are fed with a mixture of granular protein feed and corn (the mass ratio of granular protein feed to corn is 4:1) throughout the whole process of crab farming. Feed once a day at 4-5 pm. During the high temperature period in summer and autumn, feed continuously for two days and then stop for one day. The feeding amount is 10% of the weight of the crabs in the pond in the early stage, 8% in the middle stage, and 6% in the late stage (the early stage refers to the period from the release of seedlings to the end of April, the middle stage refers to May to August, and the late stage refers to September to the end of farming). The weight of the crabs is calculated by random sampling every month.

[0080] Mandarin fish are fed with granular protein feed throughout the breeding process, twice a day, at 6-7 am and 5-6 pm. The feeding amount is 3% of the mandarin fish pond volume.

[0081] (6) Aquatic plant management: When patrolling the pond every day, pay attention to the growth of aquatic plants, apply fertilizer or cut off the aging aquatic plants to keep them fresh and tender. For ponds where aquatic plants are not growing well, appropriate fertilizer should be applied to the aquatic plant area. Areas with insufficient aquatic plants should be replanted or transplanted in a timely manner, and the aquatic plants in the pond should be arranged in a sparse and dense manner with a reasonable layout. The area of ​​aquatic plants should be maintained between 50% and 60% of the entire water surface. When the pond is closed due to excessive aquatic plants, several waterways in the north-south direction should be opened to facilitate the flow of water in the pond, maintain a good ecological environment in the pond, and facilitate feeding and management.

[0082] (7) Water level control: In order to increase the water temperature in spring and promote the growth of river crabs, the water level can be controlled at 0.5-0.6m. In summer and autumn, the water temperature is higher and the depth of the pond water should be maintained at 1.2-1.5m (after the release of mandarin fish fry, the high temperature period in summer is entered. Taking into account the growth of mandarin fish and river crabs, the water level should not be lower than 1.2m). The water quality should be kept fresh throughout the process, and the aerator should be turned on frequently to maintain sufficient dissolved oxygen. The dissolved oxygen in the pond water should be maintained above 5mg / L. The pH value of the pond water should be maintained at 7.5-8.5. Change the water once a week in spring and once every 3 days in summer. In case of continuous high temperature, the water should be changed every day. In autumn, when the weather is hot, change the water every 2 days, and the amount of water changed should account for 1 / 3 of the total water area.

[0083] (8) River crab fishing: River crab fishing starts in early October. During the fishing period, the pond water level can be appropriately lowered to take into account the cultivation of mandarin fish. A combination of hand catching and ground trap fishing can be used.

[0084] (9) Mandarin fish fishing: After crab fishing, in late November to December, mandarin fish have basically reached the commercial fish size of 450g-700g / tail. They are caught by dragnet and then sold in the dry pond.

[0085] In this embodiment, the pond area is 15 mu, the net enclosure area for mandarin fish culture is 1.2 mu, the total input of mandarin fish fry is 10,000, the recapture rate is 86%, and the average weight is 550g / tail. The total catch and sale of mandarin fish is 4730kg, the net profit of sales is 95,000 yuan, and the catch of river crab is 1600kg, the net profit of sales is 52,000 yuan, the output and quality of river crab culture are not affected by the net enclosure culture of mandarin fish, the profit of mandarin fish is a net increase in pure profit, and the economic benefit is significantly increased.

[0086] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for improving the uniformity of adult mandarin fish by culturing mandarin fish in a net enclosure in a river crab intensive culture pond, characterized in that: The following steps are involved: (1) Pond conditions: The river crab breeding pond is east-west oriented, with an area of ​​15 mu. The embankment around the breeding pond is 1.8 m higher than the bottom of the surrounding ditch, the top width of the embankment is 2.0 m, and the slope ratio of the embankment is 1:2.5; (2) Preparation before breeding: In winter, drain the pond water, clean the pond, disinfect and dry the pond first, then apply fertilizer, set up escape prevention walls and plant Elodea. The planting area is outside the gabion fence, and no planting is done inside the fence. After the aquatic plants grow normally, crabs are put in. 1.2 mu of gabion fence is set up in the southwest corner of the pond. The gabion is buried 15 cm from the bottom of the pond. The fishing net fence is 1.8 m high. A plastic escape prevention board is placed 20 cm from the top of the fishing net fence. An impeller aerator is installed in the center of the fence. Four aeration plates are evenly set up near the fishing net and 0.5-0.6 m above the bottom of the pond. (3) Crab stocking: After the growth of the aquatic plant Elodea stabilizes, continue to inject new water, with the water level at 50-60 cm and the water temperature maintained at around 10°C. In late January, 1,500 crabs are stocked per mu, with a size of 80-120 per kg. (4) Release of Mandarin fish fry: In early June, purchase 30 fry / catties of Mandarin fish fry that have been acclimated to feed on pelleted feed and place them at 800 m 2 A total of 10,000 fish were placed in the gabion fence; (5) Feeding: During the whole process of crab farming, the crab is fed with a mixture of granular protein feed and corn, with a specific mass ratio of granular protein feed to corn of 4:1; the crab is fed once a day at 4-5 pm. During the high temperature period in summer and autumn, the crab is fed for two consecutive days and then stopped for one day. The feeding amount is 10% of the body weight of the crab in the pond in the early stage, 8% in the middle stage, and 6% in the late stage; the early stage refers to the period from the release of seedlings to the end of April, the middle stage refers to May to August, and the late stage refers to September to the end of farming; the crab weight is calculated by random sampling every month; during the whole process of mandarin fish farming, the crab is fed with granular protein feed twice a day, at 6-7 am and 5-6 pm; the feeding amount is 3% of the stock of mandarin fish in the pond; (6) Aquatic plant management: When patrolling the pond every day, pay attention to the growth of aquatic plants, apply fertilizer or cut off aging aquatic plants to keep them fresh and tender; in ponds where aquatic plants are not growing well, apply fertilizer appropriately in the aquatic plant area, and timely replant or transplant the areas where aquatic plants are insufficient, and strive to make the aquatic plants in the pond sparse and dense, with a reasonable layout; the area of ​​aquatic plants should be maintained between 50% and 60% of the entire water surface. When the pond is closed due to excessive aquatic plants, several north-south waterways should be opened to facilitate the flow of water in the pond, maintain a good ecological environment in the pond, and facilitate feeding and management; (7) Water level control: In spring, in order to increase the water temperature and promote the growth of river crabs, the water level can be controlled at 0.5-0.6m. In summer and autumn, when the water temperature is higher, the depth of the pond water should be maintained at 1.2-1.5m. After the mandarin fish fry are released, the high temperature period of summer comes. Taking into account the growth of mandarin fish and river crabs, the water level should not be lower than 1.2m. During the whole process, the water quality should be kept fresh, the aerator should be turned on frequently, the dissolved oxygen should be kept sufficient, and the dissolved oxygen in the pond water should be kept above 5mg / L; the pH value of the pond water should be maintained at 7.5-8.5; the water should be changed once a week in spring and once every 3 days in summer. In case of continuous high temperature, the water should be changed every day. In autumn, when the weather is hot, the water should be changed every 2 days, and the amount of water changed should account for 1 / 3 of the total water area; (8) River crab fishing: River crab fishing starts in early October. During the fishing period, the pond water level can be appropriately lowered to take into account the cultivation of mandarin fish. The crabs can be caught by hand and by trapping. (9) Mandarin fish fishing: After crab fishing, in late November to December, mandarin fish have basically reached the commercial fish size of 450g-700g / tail. They are caught by dragnet and then sold in the dry pond.

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