Ecological breeding method for river crab by using pond with floating snails for initial breeding

Abstract

The present application belongs to the technical field of aquaculture, and discloses a kind of river crab ecological breeding matching method of floating snail original pond propagation cultivation, river crab is caught crab before stocking pond cleaning;Lay "eye" type imitation lawn cloth;Partition type grass planting, net cover type grass growing;Build suspended type floating net framework, floating snail seed snail release;Water quality regulation and flow control;Carry out bait cultivation and disease prevention.The present application realizes high-efficiency propagation cultivation of floating snail original pond on the basis of river crab ecological breeding, through measures such as releasing floating snail seed snail, innovating water grass planting process, developing floating snail propagation cultivation facilities, etc., combines grass planting and snail cultivation organically, reduces bait cost while improving water quality, improves river crab yield and quality, thereby providing a new idea for realizing high-quality river crab breeding.

Description

TECHNICAL FIELD

[0001] The application provides a river crab ecological breeding matching method of floating snail primary pool propagation and cultivation, and belongs to the technical field of river crab breeding. The method comprises the following steps: 1) preparation before grass planting: laying a “eye” type artificial lawn cloth; 2) separated grass planting, net cover type grass planting; 3) building a suspended floating net frame, and adjusting water to cultivate snails. The method provided by the application innovates the water and grass planting process, introduces a new snail variety, organically combines grass planting and snail cultivation, effectively reduces the river crab breeding cost, improves the river crab yield and quality, and improves the economic benefit of river crab ecological breeding. BACKGROUND

[0002] In the process of river crab ecological breeding, grass planting and snail releasing are necessary processes. One of the most important works in the process of river crab breeding every year is water and grass planting and management. Good grass-water-river crab. Secondly, the snails, which are used to purify water quality, are used as ecological live bait for river crabs, which can supplement the nutrition of river crabs and promote the development of river crabs.

[0003] Planting water grass in a crab pond can provide fresh green feed for river crabs and increase dissolved oxygen through photosynthesis, and can also create an ideal habitat for river crabs during the molting period to avoid enemies. Water grass is planted 7-10 days after pond disinfection, and three kinds of water grass, i.e. elodea nuttallii, azolla filiculoides and vallisneria, are planted together. In recent years, with global warming, long-term low temperature in spring and persistent high temperature in summer have become the norm. Extreme weather makes the planting and management of water grass a difficult problem in river crab breeding. If not properly managed, two common problems will occur. The first problem is that the water grass in the crab pond has poor vitality, and the water grass will die in summer, which will cause the river crabs to lack grass during the molting period of the 4th and 5th shells, seriously affecting the survival of the river crabs, reducing the survival rate, and resulting in low yield and loss of the breeders. The second problem is that the water grass grows too vigorously in the crab pond, and the pH of the water body is too high. Due to the existence of the difference between photosynthesis during the day and respiration at night, the crab pond will be short of oxygen, the overgrown water grass will occupy the esophagus of the river crabs and prevent them from feeding on the food or fresh ice fish at the bottom of the pond, which will attract the gathering of enemy birds such as herons and aggravate the damage to the river crabs. It is time-consuming and labor-intensive to cut and collect the grass, and the labor cost increases. Due to the overgrowth, the lower part of the water grass is not exposed to light, which hinders the growth of the water grass, causes the roots to rot and the grass to rot, and damages the water quality. The increase of harmful substances such as ammonia nitrogen and nitrite nitrogen in the pond is not conducive to the river crabs, which will eventually lead to the damage of the river crabs.

[0004] The snail is put in the crab pond, which purifies water quality and maintains fresh water quality on one hand, and the snail is rich in nutrition and has high utilization rate, which is an ideal high-quality fresh animal bait that river crab likes most, can promote the rapid growth of river crab and improve the market specification of adult crab. The snail is usually put in the crab pond before and after Qingming Festival, and the amount of the snail is 200-250 kg per mu. The snail is also known as field snail and its scientific name is Amullus squarrosus. The traditional snail put in the crab pond is usually caught in freshwater river, and the drag net is used to scrape the bottom of water, filter and wash the captured objects, which brings great adverse effects on the survival and breeding environment of the bottom organisms. The drag net fishing seriously destroys the ecological bottom habitat. In the long run, it is urgent to find a substitute to fully meet the needs of river crab growth. The floating snail, also known as floating snail, has high nutritional value and does not need to be fed. It mainly feeds on water grass clippings, pond leftover bait, river crab feces and plankton, effectively purifying the water quality of the pond. It can breed and lay eggs above 10℃, and has fast breeding and growth, which can continuously meet the feeding amount of river crab. At the same time, compared with the hard shell snail, the floating snail has tender meat and thin shell, and has better palatability, which reduces the difficulty of river crab feeding. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a river crab ecological breeding matching method of floating snail original pond breeding and cultivation.

[0006] The present application is implemented as follows: a river crab ecological breeding matching method of floating snail original pond breeding and cultivation, which comprises the following steps: cleaning the pond before the river crab is put in; laying "eye" type imitation lawn cloth; separating type grass planting and net cover type grass cultivation; building a suspended type floating net frame; floating snail planting; water quality adjustment and water flow regulation; bait cultivation and disease prevention.

[0007] Further, the "eye" type imitation lawn cloth has a width of 2 meters and a thickness of 2 cm, and is distributed at a predetermined interval of 1 meter to promote the hiding and growth of river crab.

[0008] Further, the method comprises the steps of: separating type grass planting and net cover type grass cultivation; setting a barrier net in the pond to divide the pond into an A area and a B area, and planting different types of water grass in the two areas respectively; the barrier net is made of nylon or PE material and has good ultraviolet resistance and corrosion resistance.

[0009] Further, the A area mainly plants elodea, and the B area mainly plants hygroryza arborescens; the planting time and growth conditions of the two types of water grass should be considered scientifically according to their respective growth needs; the water quality and temperature are adjusted according to the growth temperature, light demand and nutrient salt content of elodea and hygroryza arborescens.

[0010] Further, a suspended net frame is built in the pond; the frame is made of rust-proof steel or PVC material, including the top, both sides, and using foam floats or empty mineral water bottles as buoyancy support to ensure the stability of the frame.

[0011] Further, the top of the suspended net frame is made of fishing net material with wear-resistant and bird-proof properties, and the mesh size is 3-5 cm; the frame is used to block the white egret water birds, while also allowing the river crab bait to pass smoothly; the edge of the net cover is provided with adjustable pull ropes or fixing devices to facilitate opening or closing.

[0012] Further, during the peak period of water grass growth from June to August, the water grass is crushed into 1-3 cm long powder and thrown into the suspended net frame for the snail to feed; the powder is crushed by mechanical or manual method and evenly distributed on the suspended net frame by a specific distribution device.

[0013] In combination with the above technical solutions and the technical problems solved, the technical solutions to be protected by the present application have the following advantages and positive effects:

[0014] Firstly, the present application focuses on the combination of snail cultivation and water grass cultivation in river crab ecological breeding, which can significantly reduce the cost of river crab bait, improve the water quality of river crab breeding, maintain the stability of the good ecological environment of river crab, improve the quality and size of river crab, and improve the comprehensive benefits of river crab ecological breeding.

[0015] Secondly, the pond layout method for river crab breeding provided by the present application has the following significant technical progress:

[0016] 1. Optimized ecological environment: By laying "eye" type imitation lawn cloth at the bottom of the pond, the natural ecological environment of river crab is simulated, providing good hiding and growing space for river crab, which helps to improve the survival rate and growth rate of river crab.

[0017] 2. Scientific grass planting strategy: The method of separate grass planting and net cover type grass growing is adopted, and the water grass is planted scientifically according to the growth demand, which effectively utilizes the pond space and provides rich food source and good ecological environment for river crab.

[0018] 3. Effective bird protection: The suspended net frame can effectively prevent the predation of white egret and other water birds on river crab, improve the survival rate of river crab, and also allow the river crab bait to pass smoothly, reducing the breeding cost.

[0019] 4. Standardized bait management: During the peak growth period of water grass, the water grass is crushed into 1-3 cm long powder and put into the floating net frame for the snail to feed. A novel and standardized bait management method is adopted to improve the utilization rate of bait and help keep the pond water clean.

[0020] This pond arrangement method for river crab breeding combines the ecological habits of river crabs and breeding techniques, achieving an ecological, scientific, efficient and economic breeding method, which brings significant technological progress to the river crab breeding industry.

[0021] The advantage of this pond arrangement method is that it provides a good environment for the growth of river crabs. The laying of imitation lawn cloth helps the hiding and growth of river crabs, while the separated grass planting and net cover type grass growing provide growth space for different types of water grass, meeting the needs of river crabs at different stages. In addition, the adjustment of water quality and temperature can further improve the growth conditions of river crabs. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the flow chart of the ecological breeding method of river crabs provided by the embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0024] The ecological breeding method of river crabs provided by the present application includes laying "eye" type imitation lawn cloth on the bottom of the pond. The imitation lawn cloth has the characteristics of water permeability, corrosion resistance and tensile resistance, and is fixed by 1mm steel wire rope and "U" type ground nails. The "eye" type imitation lawn cloth has a width of 2 meters and a thickness of 2 cm, and is distributed at a predetermined interval of 1 meter to promote the hiding and growth of river crabs.

[0025] It includes the means of separated grass planting and net cover type grass growing, setting a barrier net in the pond to divide the pond into A and B areas, and planting different types of water grass in the two areas respectively; the barrier net material is made of nylon or PE material, which has good ultraviolet resistance and corrosion resistance.

[0026] Among them, A area mainly plants elodea, and B area mainly plants hygroryza arborescens; the planting time and growth conditions of these two types of water grass should be considered scientifically according to their respective growth needs; considering the growth temperature, light demand and nutrient salt content of elodea and hygroryza arborescens, the corresponding water quality and temperature are adjusted.

[0027] A suspended net frame is built in the pond; the frame is made of rust-proof steel or PVC material, including the top, both sides, and uses foam floats or empty mineral water bottles as buoyancy support to ensure the stability of the frame.

[0028] The top of the suspended net frame is made of fishing net material, which has wear-resistant and bird-proof properties, and the mesh size is 3-5 cm; the frame is used to block the white egret, and also allows the river crab bait to pass smoothly; the edge of the net cover is provided with adjustable pull ropes or fixing devices to facilitate opening or closing.

[0029] During the peak period of water grass growth from June to August, the water grass is crushed into 1-3 cm long powder, and is put into the suspended net frame for the snail to feed; the powder is crushed by mechanical or manual method, and is uniformly distributed on the suspended net frame by a specific distribution device.

[0030] As another optimization scheme of the present application, as shown in Figure 1 The ecological breeding method for river crab provided by the snail original pond propagation and cultivation of the present application comprises the following steps:

[0031] S101: clearing the pond before releasing the river crab;

[0032] S102: laying "eye" type imitation lawn cloth;

[0033] S103: separated grass planting, net cover type grass planting;

[0034] S104: building a suspended net frame, and releasing snail seeds;

[0035] S105: water quality adjustment and water flow regulation;

[0036] S106: bait cultivation and disease prevention.

[0037] As an optimization scheme of the present application, it further comprises:

[0038] Before releasing the river crab, the pond is cleared with lime and bleaching powder; Nitellopsis sanguinea is planted in the ring ditch of the ring ditch type pond, and Hydrilla verticillata is planted on the field plate; oval chlorella and enhanced EM bacteria are applied in the morning on sunny days, to build a benign bacteria-algae symbiotic system;

[0039] Snail seed release: for new pond mouths and ponds lacking snails, the snail seed release should be completed before and after the Qingming Festival, and healthy snails with undamaged shells are selected for release, and are released after pond fertilization, and are uniformly released in the whole pond;

[0040] Water quality adjustment and water flow regulation: use lime and biological organic acid to adjust the pH value of the water body, and use water wheel type oxygenation machine to push water and replace water, to keep the water body in a flowing state during the snail breeding period;

[0041] Bait biological cultivation: early use of enhanced EM bacteria fermented soybean meal for water and fertilizer, cultivate bait biological;

[0042] Disease prevention: timely use of vitamins, biological organic acids to prevent and control river crab stress injury in high temperature season.

[0043] The river crab ecological breeding matching method provided by the floating snail original pool propagation cultivation of the embodiment of the application comprises the following steps:

[0044] (1) 7-10 days before the river crab is released, the pond is cleaned with water using composite bleaching powder (15-20 kg) and quicklime (80-100 kg / mu). 100 kg of base fertilizer (fermented organic fertilizer) is applied per mu, and composite water grass of elodea and hygroryza ovals is planted: elodea is planted from January to February, and hygroryza ovals is planted from March to April; 1 day before planting the water grass, the water level is lowered to about 10 cm, the elodea is planted in the flat bottom pond, the distance is 1.5-2.5 m, the amount of grass is 10-15 kg / mu, and the hygroryza ovals is planted in the ring ditch of the ring ditch pond. Ellipsoidal chlorella and enhanced EM bacteria are applied once every 7-10 days in the morning on sunny days, and a benign bacteria-algae symbiotic system is constructed.

[0045] (2) Floating snail seed release: the old river crab breeding pond mouth generally does not need to release floating snail seeds. For new pond mouths and ponds with lack of floating snails, the seed release should be completed before and after the tomb-sweeping festival, healthy snails with no damage to the shell are selected for release, and the release is carried out 5-7 days after the pond is fertilized, the release amount is 2.0-2.5 kg / mu, and the release is uniformly carried out in the whole pond.

[0046] (3) Water quality regulation and flow regulation: the transparency is kept at 30-40 cm, the pH is 7.5-8.5, and the pH of the water body is adjusted using quicklime and biological organic acid. Small ball algae (1L / mu) and enhanced EM bacteria (2L / mu) are used once every 7-10 days from March to May to optimize and construct the bacteria-algae symbiotic system and regulate the water quality; enhanced EM bacteria (2L / mu) and small ball algae (1L / mu) are applied once every 5-7 days in the high temperature season. New water is added in time, when the water quality of the pond is poor, new water should be added in time; the water body is kept in a flowing state through the water car type oxygenator water pushing and water changing measures.

[0047] (4) Bait organism cultivation: In the early stage, use soybean meal fermented by enhanced EM bacteria to cultivate bait organisms. In June-August, grind the waterweeds such as Elodea and Alternanthera into powder and evenly throw them into the pond to increase the content of organic matter available to the ramshorn snails. Apply calcium phosphate once every half month to supplement calcium, which is beneficial to the growth and reproduction of the ramshorn snails. The amount of bait organisms to be thrown in is dynamically adjusted according to the feeding condition of the ramshorn snails, generally once every 3-5 days. When the water temperature exceeds 30°C, stop throwing in to avoid water pollution.

[0048] (5) Disease prevention: Use vitamins and bio-organic acids in time to prevent and control the stress injury of river crabs in high-temperature seasons. Apply lime (50 kg / acre) to disinfect the water once every half month to achieve the purpose of disease prevention.

[0049] Example 1

[0050] 1. First, select a rectangular pond with a size of about 30m x 20m. Lay "eye" type imitation lawn cloth on the bottom of the pond at intervals of 1 meter. The cloth is made of water-permeable, corrosion-resistant and tensile material, with a specification of 2 meters wide and 2 cm thick. Fix the imitation lawn cloth with 1 mm steel wire and "U" type ground nails to ensure that it will not be washed away by the water flow.

[0051] 2. Set a nylon or PE material barrier in the pond to divide the pond into A and B areas. In the A area, mainly plant Elodea, and in the B area, mainly plant Hygroryza. The planting and maintenance of these two kinds of waterweeds should be adjusted according to their respective growth needs to adjust the corresponding water quality and temperature.

[0052] 3. Build a suspended floating net framework made of rust-resistant steel or PVC material in the pond, which includes the top, both sides, and uses foam floats or empty mineral water bottles as buoyancy support. The top is made of fishing net material with a mesh size of 3-5 cm to block water birds such as egrets while allowing the bait of river crabs to pass through smoothly.

[0053] 4. During the peak growth period of waterweeds from June to August, grind the waterweeds into 1-3 cm long powder and throw them into the suspended floating net framework for the ramshorn snails to feed. Use mechanical or manual methods to grind and evenly distribute them on the suspended floating net framework through a specific distribution device.

[0054] Example 2

[0055] 1. Select a circular pond with a diameter of about 50m. Lay "eye" type imitation lawn cloth on the bottom of the pond at intervals of 1 meter, with a specification of 2 meters wide and 2 cm thick. Fix it with 1 mm steel wire and "U" type ground nails.

[0056] 2. Set a ring-shaped net made of nylon or PE material in the pond to divide the pond into an inner circle A area and an outer circle B area. In the A area, mainly grow Hydrilla verticillata, and in the B area, mainly grow Elodea.

[0057] 3. Build a circular suspended net frame made of PVC material in the pond, which includes a top, two sides, and uses empty mineral water bottles as buoyancy support. The top is made of fishing net material with a mesh size of 3-5 cm to block water birds while allowing river crab bait to pass smoothly.

[0058] 4. At the peak of water grass growth, crush the water grass into powder and throw it into the suspended net frame for the snail to feed. The length of the powder should be about 1-3 cm and evenly distributed on the suspended net frame through a specific distribution device.

[0059] As an optimization scheme of the present application, the method provided by the present application is specifically:

[0060] 1. Preparation before planting grass: laying "eye" type artificial lawn cloth

[0061] After the pond is cleaned and dried, the "eye" type artificial lawn cloth is distributed on the pond bottom, with a width of 2 meters and a thickness of 2 cm. The "eye" type artificial lawn cloth has four horizontal rows with a row spacing of 1 / 5 of the longitudinal length of the pond, and two vertical rows with a distance of 4 meters from the longitudinal slope of the pond. The artificial lawn cloth is threaded with a 1mm steel wire rope, and then "U" type ground nails are inserted into the pond bottom along the artificial lawn cloth, with a horizontal interval of 1 meter and a vertical interval of 1 meter. The edge-inserted ground nails are required to be perpendicular to the steel wire rope and inserted into the ground until the tail tip, fully fixing the artificial lawn cloth.

[0062] The "U"-shaped imitation lawn cloth is laid on the bottom of the pond, which is beneficial to the survival and growth of river crabs. First, the river crabs are separated from the silt at the bottom of the pond, and the river crabs after molting have clean bottom plates, green backs and white bellies, and fewer crabs with black bottom plates and yellow bottom plates, and the appearance and color are significantly improved; second, in the traditional crab pond, the water grass grows vigorously during the high temperature period in summer, and the whole pond is covered with water grass, which requires a lot of work to trim and cut the head. The "U"-shaped imitation lawn cloth is placed, which can inhibit the growth of water grass under the lawn cloth (such as non-production required golden fish algae, which will entangle normal water grass, grow rapidly and occupy the territory and nutrients of high-quality water grass, which is time-consuming and laborious to handle), and the lawn cloth covered area does not need to be specially maintained, the total area of pond water grass can be controlled, and the difference between photosynthesis during the day and respiration at night can be controlled; third, the water grass covering the surface of the traditional crab pond seriously hinders the feeding of river crabs, and part of the bait (such as ice-fresh fish pieces) falling on the water grass will attract a large number of white storks to come to feed and indiscriminately kill river crabs, resulting in low yield of crab ponds. The "U"-shaped imitation lawn cloth is placed, and the area serves as a fixed feeding channel for the whole cultivation, guiding workers to feed and river crabs to feed at fixed points, forming a good conditioned reflex mechanism; fifth, the "U"-shaped imitation lawn cloth placement area can be used as a placement area for river crabs or supporting blue shrimps and Macrobrachium rosenbergii cultivation and fishing, and there is no need to artificially cut grass to open a way to destroy the pond water grass ecological placement area.

[0063] 2. Separated grass planting, net cover type grass growing

[0064] After laying the imitation lawn cloth in the pond, a barrier net is laid at 2 / 5 of the pond, the barrier net has a mesh size of 0.5 cm, a net height of 1 meter, a top anti-escape edge, and a bottom edge embedded in the bottom mud of the imitation lawn cloth edge by 10-15 cm. In this way, the pond is divided into two areas, A and B. According to the scientific consideration of the temperature required for the growth of different varieties of water grass, which results in the speed of growth, Euryale ferox and Hydrilla verticillata are planted respectively. The A area is the Euryale ferox planting area, which accounts for 2 / 5 of the pond area and is planted with Euryale ferox. Euryale ferox is resistant to low temperature but not high temperature, and can grow in winter, so Euryale ferox is planted in January and February, and crab fry can be released in late February and early March, which is the best place for crab fry to avoid natural enemies and also a natural plant protein bait for crab fry; the B area is the Hydrilla verticillata planting area, which accounts for 3 / 5 of the pond area and is planted with Hydrilla verticillata. Hydrilla verticillata requires a certain temperature for germination and growth and is relatively resistant to high temperature, so Hydrilla verticillata is planted in March and April, and the barrier net can be removed when Hydrilla verticillata grows in May and June, allowing the crab fry to move freely in the whole pond.

[0065] When the water temperature is high in summer, the growth of elodea is inhibited, the roots are loose, and the whole body is uplifted by the buoyancy of deepening water level, and often easy to float grass death. Therefore, the network cover can be tried in the early stage of planting. The network cover is made of fishing net material, with a mesh width of 20 cm. After planting water plants, the whole network is laid on the elodea, close to the roots, and each cluster of elodea roots is pressed with a ground nail. Two nails are placed around each cluster. The network cover covers the A area of the pond, fixes the whole elodea, and ensures the root of the water plant in summer. The growth of water plants is good, and the water quality is high. The more stable the water quality is, the better the river crab grows and feeds under the water plants, and at the same time, it can avoid the natural enemies such as water birds, safely molt, and has a high survival rate.

[0066] 3. Preparation before releasing snails: build a suspended floating net frame

[0067] Floating snails, unlike traditional bottom-dwelling snails, are buoyant and prefer to eat plant debris. In order to better promote their survival and growth, a telescopic floating net frame corresponding to the bottom "eye" type imitation lawn cloth is built before releasing snails for their attachment, water surface floating feeding, and observation of their feeding conditions.

[0068] The suspended floating net frame is generally three-sided.

[0069] First, the top is the same width as the "eye" type imitation lawn cloth, made of fishing net material with a mesh width of 3-5 cm. A circle of net surface is connected every half meter with a diameter of 8-10 cm foam float ball or empty mineral water bottle as buoyancy support to drive the main net surface to rise and fall with the water level. The hollow fishing net material not only allows the river crab bait to pass through the imitation lawn cloth food channel directly below, but also serves as a bird net to block the feeding of water birds such as egrets. During the summer high-temperature period, the floating net surface can block part of the sunlight, reducing the underwater temperature, and playing a similar role as a sunshade net.

[0070] Second, the two sides are the same width as the "eye" type imitation lawn cloth and perpendicular to it, with a mesh width of 0.5 cm, belonging to a dense net type fishing net. The upper part of the two sides relies on the buoyancy of the top floating net, and the lower part is suspended with lead sinkers. The height is 0.3 meters, and the four corners are connected with a circular ring, which is fixed by a 1.5-meter-long galvanized steel pipe with a thickness of 3 mm and a diameter of 2 cm inserted into the pond bottom. Due to the existence of the circular ring, the suspended floating net can freely rise and fall with the water level of the crab pond. During the early stage of river crab breeding, the water level is low, about half a meter deep, and the side net blocks part of the water grass growing into the imitation lawn cloth area, which helps the water grass grow in a grid pattern. However, the side net is 0.2 meters away from the bottom of the pond due to the buoyancy, which does not affect the river crab's free access to the water grass area and the river crab's food channel area. During the middle stage of river crab breeding, the water level gradually rises to 1 meter, and the floating net rises due to the buoyancy. The upper part blocks the water grass from invading the river crab's food channel, and the lower part is completely unblocked, leaving the imitation lawn cloth area above it empty. The sunlight can directly reach the roots of the water grass, effectively improving the bottom quality and promoting the growth of the water grass root system.

[0071] Thirdly, from June to August, the peak period of water grass growth, the water grass in the crab pond is trimmed, and the water grass such as elodea and water hyacinth is crushed into powder and thrown into the floating frame for the snail to feed; the amount of throwing is 3-5 times a day; when the water temperature exceeds 30℃, stop throwing, and remove the suspended net before the river crab is caught in October, which does not affect the normal catching of river crab.

[0072] Fourthly, the crab pond brings some benthic snail larvae (square ring snail) with the planting of water grass or water belt, and cooperates with the later thrown floating snail (elliptical radish snail), which provides a high-quality place for the snail to attach, inhabit and reproduce. The suspended net and the corresponding simulated lawn cloth provide a high-quality place for the snail to attach, inhabit and reproduce. From the water surface to the underwater, both kinds of snails are evenly distributed and sufficient in amount. River crab no longer needs to run around to find snails, which reduces the physical consumption of river crab and reduces the probability of river crab contacting the bottom mud during the process of finding snails at the bottom, resulting in yellow or black bottom plate.

[0073] 4Floating snail breeding, ecological snail breeding

[0074] For the new pond of river crab breeding or the pond lacking of floating snail, it is appropriate to choose to throw healthy snail with no damage to the shell before the Qingming Festival in April. The amount of throwing is 2.0-2.5kg / acre, and the whole pond is evenly thrown. As an important complementary species of traditional benthic snail, floating snail breeding through suspended net provides sufficient snails for river crab to feed, reduces the snail of river crab, and effectively protects the water grass. For 10 mu, install 0.75kw water car type oxygenator at the opposite angle of the crab pond, and keep the water in flowing state during the breeding period of floating snail through oxygenation and water pushing.

[0075] Floating snail breeding has certain requirements for water quality, and the transparency should be kept at 30-40cm, and the pH value should be 7.5-8.5, which is beneficial to its breeding. One week before throwing the snail, use the fermented soybean meal of enhanced EM bacteria to sprinkle the pond water at the rate of 3kg of fermented soybean meal per mu of water depth, which provides sufficient feed for the following snail larvae. In the first 3-5 months of river crab breeding, small ball algae 1L / acre and enhanced EM bacteria 2L / acre are used once every 7-10 days; in the middle and late period of river crab breeding, enhanced EM bacteria 2L / acre and small ball algae 1L / acre are applied once every 5-7 days, and calcium fertilizer 0.5kg / acre with calcium dihydrogen phosphate as the main component is applied once every 15 days to supplement calcium, which is beneficial to the growth and reproduction of floating snail.

[0076] Example 1:

[0077] In 2023, the invention carried out preliminary test in Jiangsu Noah Ark Agricultural Technology Co., Ltd. Changzhou Base, which carried out scientific research cooperation with Freshwater Fisheries Research Center of Chinese Academy of Fishery Sciences. During the test, the effect of 2:3 separated planting of Elodea and Hydrilla verticillata was good. In the early stage, the crabs were placed in the Elodea area and fed well. The growth of Elodea was relatively fixed, and there was little summer floating grass. After removing the water grass barrier net in May, Hydrilla verticillata had grown up. In summer, the water quality was maintained stable by using Hydrilla verticillata as the main water grass plate, which ensured the smooth molting and over-summering of river crabs. At present, the river crabs have not been released into the pond, but the overall growth is good. The imitation lawn cloth laid in the crab pond has good weed suppression effect, and the feed can directly reach the bottom of the pond. There is no need to cut grass and clean the area separately for catching juvenile shrimps. During the test, it was found that the floating net was easy to get dirty. The feeding method is different from the past manual boat feeding. The bamboo pole for supporting the boat can damage the arrangement of the imitation lawn cloth at the bottom of the pond, and the floating net can hinder the boat. Therefore, by learning from the experience of using agricultural unmanned aerial vehicles for feeding in crab fry ponds, the main feeding channel is fixed in the imitation lawn cloth area, and the feeding of adult crabs is precise and convenient. The pond is equipped with a floating net, and the bottom-dwelling snails and floating snails can be seen attached to the floating net. The situation of feeding river crabs with fresh fish bait being stolen by white egrets has been improved, including the reduction of night-time patrolling and flying of gray egrets. At the end of August, a yield test was conducted on the river crab test pond to observe the effect of grass and snail breeding on promoting river crab ecological breeding. The results showed that 101 and 102 test ponds with 80-100 kg of Chinese mitten crab "Noah No. 1" per mu, 1800 crabs per mu, and the yield was more than 200 kg per mu, with an average size of more than 150 g per mu.

[0078] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any modification, equivalent replacement and improvement within the technical range disclosed in the present application, which is within the spirit and principles of the present application, should be covered within the protection scope of the present application.

Claims

1. A method for ecological aquaculture of river crabs using floating snails in a pre-pond propagation and cultivation system, characterized in that, It includes pond cleaning before releasing juvenile Chinese mitten crabs; laying "mesh"-shaped artificial turf cloth; dividing the grass planting area and cultivating grass with a net cover; building a suspended floating net framework and releasing floating snails and breeding snails; water quality regulation and water flow control; carrying out bait cultivation and disease prevention; Lay the "mesh"-shaped artificial turf cloth at the bottom of the pond and fix it with 1mm steel wire ropes and "U"-shaped ground nails; the "mesh"-shaped artificial turf cloth has a specification of 2 meters in width and 2 cm in thickness and is distributed at a predetermined interval of 1 meter; By means of dividing the grass planting area and cultivating grass with a net cover, set up a barrier net in the pond to divide the pond into Area A and Area B, and plant different types of aquatic plants in these two areas respectively; the barrier net material is made of nylon or PE; Place the "mesh"-shaped artificial turf cloth, the shading can inhibit the growth of aquatic plants under the artificial turf cloth; place the "mesh"-shaped artificial turf cloth, this area serves as a fixed feeding channel throughout the breeding process, guiding workers to feed at fixed points and the Chinese mitten crabs to feed at fixed points, forming a good conditioned reflex mechanism.

2. The method according to claim 1, characterized in that, Among them, Elodea canadensis is planted in Area A, while Hydrilla verticillata is planted in Area B.

3. The method according to claim 1, characterized in that, It includes building a suspended floating net framework in the pond; the framework is made of rust-proof steel or PVC, including the top and both sides, and uses foam floating balls or empty mineral water bottles as buoyancy supports.

4. The method according to claim 3, characterized in that, The top of the suspended floating net framework is made of fishing net material, which has the characteristics of wear resistance and bird prevention, and the mesh size is set to 3-5 cm; the framework is used to block water birds and at the same time allow the bait of Chinese mitten crabs to pass through smoothly; adjustable draw ropes or fixing devices are set at the edge of the net cover.

5. The method according to claim 1, characterized in that, It includes during the peak growth period of aquatic plants from June to August, crushing the aquatic plants into fragments with a length of 1-3 cm and putting them on the suspended floating net framework for floating snails to forage; the fragments are crushed by mechanical or manual means and evenly scattered on the suspended floating net framework through a distribution device.

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