CN111066705A

CN111066705A - Improved river crab ecological breeding method

Info

Publication number: CN111066705A
Application number: CN201911290377.4A
Authority: CN
Inventors: 朱同林; 杜富宽; 陈如国; 文执信; 徐钢春; 徐跑
Original assignee: Jiangsu Red Grease Crab Co ltd
Current assignee: Jiangsu Red Grease Crab Co ltd
Priority date: 2019-12-16
Filing date: 2019-12-16
Publication date: 2020-04-28

Abstract

The invention provides an improved river crab ecological breeding method, which comprises the step of water body purification treatment before breeding, wherein the purifying agent takes magnesium hydroxide as a main component, can effectively reduce the content of hydrogen sulfide in breeding water and a river channel, and has good improvement effect on over-low pH value of water quality and eutrophication; the calcium supplement agent of alkaline solution is adopted in the culture process, wherein calcium nitrate can directly supplement calcium in a culture farm, the zeolite powder can remove 95% of ammonia nitrogen in water, purify water quality, relieve the phenomenon of water transfer, and effectively adsorb harmful substances such as ammonia nitrogen, nitrite, algal toxin and the like at the bottom of the pond to play a role in calcium supplement and deodorization; the river crab culture method not only has excellent cultured adult crab quality and delicious taste, but also can realize large-scale culture with high economic benefit, and the culture diseases are reduced by more than 30%; the culture process is environment-friendly, economical and reasonable; avoids water body pollution to the maximum extent and ensures the continuous production of river crab culture.

Description

Improved river crab ecological breeding method

Technical Field

The invention relates to the technical field of agricultural cultivation, in particular to an improved river crab ecological cultivation method which can improve the cultivation quality and yield of river crabs and meet the requirements of environmental protection and sustainable development.

Background

The river crab is also called as Chinese mitten crab, is a famous and precious freshwater product, has delicious taste and rich nutrition, is deeply loved by people and has very high economic value. River crab cultivation is a relatively complex process, and various factors such as the design layout of a cultivation area (pond), the water environment, aquatic plant cultivation, the feed and time for feeding, disease prevention and the like need to be comprehensively considered for ensuring that the cultivated crabs have unique flavor of fragrance, freshness and sweetness and need to be managed in a refined way; in addition, for modern breeding, the requirements of ecological breeding are required to be met, water pollution is reduced, energy is saved, consumption is reduced, and the like, so that the requirements of large-scale breeding are met.

In order to meet the requirement of modern river crab culture, the applicant provides a river crab culture system and a culture method in Chinese patent application No. CN201710405721.4, the patent application carries out a plurality of improvements on the construction of a river crab culture hardware system and the control of the culture process, and achieves better economic benefit and social benefit, but the water body control before and after culture and the like are not involved too much, and the quality and the control of the culture water body are also very important for river crab culture, so on the basis of the prior patent technology, the applicant carries out further improvement and culture tests according to increasingly strict requirements of governments on environmental protection, and provides an improved ecological river crab culture method.

Disclosure of Invention

Aiming at the increasingly strict requirements of ecological breeding of modern river crabs, the invention aims to provide an improved ecological breeding method for river crabs, which can meet the requirements of large-scale production, ecological breeding and fine management of modern river crabs, has excellent quality of finished river crabs, saves energy, reduces consumption and well ensures the water body environment, thereby ensuring the sustainable implementation of river crab breeding.

In order to achieve the purpose of the invention, the improved river crab ecological breeding method comprises the following steps:

crab larva selection: selecting young Chinese mitten crabs in a Yangtze river system as crab seeds, and soaking for 3-5 minutes by using a 3-4% salt solution or soaking for 20-30 minutes by using potassium permanganate with the concentration of 15-20 mg per liter when stocking; the male-female ratio is 3: 1 or so;

water treatment before cultivation: 100 g/m of 1000 square meters of water²The purifying agent is a solid-liquid mixture and comprises 16 to 26 parts by weight of magnesium hydroxide, 5 to 10 parts by weight of sodium hydrogen phosphate and 20 to 50 parts by weight of water; the pH value of the purifying agent is 9.5-10.5;

culturing the crabs: planting hydrilla verticillata and elodea nutans in the crab seedling culture pond, and transplanting water peanuts on the water surface, wherein the coverage surface accounts for 30-50% of the water surface; adding fresh water 15 days before the crab seedlings are put into the pond; stocking the crab seedlings in a temporary stocking area, stocking the temporary stocking area to the breeding area after the aquatic weeds grow out, and stocking 1-1.5 kg of crab seedlings per mu;

aquatic plant cultivation and feed feeding: the hydrilla verticillata and the elodea nutans are cultivated in a dot mode, the spacing between cultivation points is 80-100 cm, and the coverage surface respectively accounts for 20% of the water surface; the total aquatic weed coverage rate in the pond is 60-70%; before Qingming, 200 kg of sterilized fresh spiral shell is put in per 667m²Uniformly throwing the snails in the whole pool in 7-8 months according to the amount of the snails stored in the crab pool and the amount of the snails per 667m²(ii) a In the early stage of cultivation, bean cake, wheat flour, silkworm chrysalis meal, fish meal or minced small fish, crushed snail and clam meat are used as raw materials and mixed into granules for feeding, or open type compound feed is used as main feed for feeding; the middle stage mainly comprises fine and green feeds such as bean cake, corn, wheat, potato, pumpkin, sweet potato, etc.; adding 50% of animal baits in the later period or feeding special compound feed for the river crabs in the later period;

putting a calcium supplement: putting a calcium supplement once in a period of 10-15 days before river crab shelling; the calcium supplement is a solid-liquid mixture, and comprises the following components in parts by weight: 16-26 parts of calcium nitrate, 5-10 parts of zeolite powder and 20-50 parts of water; the pH value of the calcium supplement is 7.3-8.3;

water quality monitoring and oxygenation: controlling the working switch and working time of the oxygen increasing device according to the water quality monitoring data; the quick lime is used for water quality adjustment, the quick lime is used once every 10-15 days, the concentration of each time is 10-15 ppm, calcium dihydrogen phosphate is applied in a matching mode, 1 time per month, and 2 kg/667 m of calcium dihydrogen phosphate is applied every time²The calcium carbonate is used in a crossed way with the quicklime;

biological agent regulation: topdressing water-regulating biological agents such as photosynthetic bacteria, bacillus, lactic acid bacteria, bifidobacterium, actinomycetes, yeast (EM), mineral substances and the like from 4 months; spraying bottom-modified biological preparations such as EM bacteria, high molecular organic polymers, oxygen increasing agents, synergistic agents and the like once every 15 days from the beginning of 6 months;

water level monitoring and adjusting: according to the water level monitoring result, adjusting the water level of the aquaculture pond in time, and keeping the depth of the pond water at 1-1.5 m;

stress prevention and control: spraying the granular feed with biological preparation dissolved water, and adding VC and polyvidone polysaccharide into the feed; in 4-5 months, ciliate is killed once by using ciliate-killing agent such as ciliate-killing agent, carapace-killing agent, ciliate-killing agent or zinc sulfate compound drug; after the yellow plum is finished, carrying out primary water body disinfection and oral administration of the medicinal bait for 3 days continuously; in 9 middle of the month, ciliates are killed once, and water disinfection and internal medicine bait are carried out.

Preferably, the breeding method can also comprise the step of polyculture of river crabs and mandarin fish, polyculture of river crabs and crayfish or polyculture of river crabs and freshwater shrimps.

More preferably, the mass content of the magnesium hydroxide in the purifying agent is 10-70%.

More preferably, the mass content of the magnesium hydroxide in the purifying agent is 30-70%.

More preferably, the mass content of the calcium nitrate in the calcium supplement is 10-70%.

More preferably, the mass content of the calcium nitrate in the calcium supplement is 20-50%.

Preferably, the step of adding the calcium supplement is to add the calcium supplement 1 time within the river crab shelling period.

According to the improved river crab culture method, water body purification treatment is carried out before culture, the purifying agent takes magnesium hydroxide as a main component, the content of hydrogen sulfide in culture water and a river channel can be effectively reduced, and the improved river crab culture method has a good improvement effect on the pH value of water quality which is too low and eutrophication; the adopted calcium supplement agent is an alkaline solution, calcium nitrate can directly supplement calcium in a farm, the zeolite powder can remove 95% of ammonia nitrogen in water, purify water quality and relieve the phenomenon of water transfer, and can effectively adsorb harmful substances such as ammonia nitrogen, nitrite, algal toxin and the like at the bottom of the pool to play a role in calcium supplement and deodorization; the river crab culture method not only has excellent cultured adult crab quality and delicious taste, but also can realize large-scale culture with high economic benefit, and the culture diseases are reduced by more than 30%; the culture process is environment-friendly, economical and reasonable; avoids water body pollution to the maximum extent and ensures the continuous production of river crab culture.

Drawings

The foregoing and other objects, features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings. Wherein:

fig. 1 is a schematic layout structure of a adult crab culture pond of a culture system used in the river crab culture method according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional view of fig. 1.

Detailed Description

The features and advantages of the present invention are described in detail below with reference to the accompanying drawings.

Referring to a layout structure schematic diagram of the river crab culture system shown in FIG. 1, the culture area (pond) is designed as a rectangular pond with an area of 20-30 mu, a pond depth of 1.5-1.8 m, a slope ratio of 1:2.5 or more and a pond ridge width of 2-3 m; in a preferred embodiment, the rectangular pool is long in the east-west direction and short in the north-south direction; planting the aquatic weeds 12 at the bottom of the pool, wherein in a preferred embodiment, the planting area of the aquatic weeds accounts for 2/3 of the area of the water body in the whole pool; when the aquatic weeds grow too densely, grass-free channels 121 with the width of 1.5-2 m can be arranged in the middle of the aquatic weeds every 10-15 m; a water inlet 141 and a water outlet 143 are arranged on the opposite corners of the rectangular pool, the plane of the pool bottom is inclined towards the water outlet, and the specific drop is about 0.5%; the water inlet and the water outlet are arranged diagonally, each pond is provided with a high-irrigation low-drainage system, and the water inlet gate and the water drainage gate are respectively arranged at two ends of the crab pond; arranging a fence net on a net sheet with the aperture of 0.88mm for the water inlet, arranging a water filtering net bag on the net sheet with the aperture of 0.45mm, and arranging a net bag on a net sheet with the aperture of 0.88mm for the water outlet; a temporary river crab fry rearing area 10 is arranged at one corner of the rectangular pool, the area of the temporary river crab fry rearing area 10 accounts for 1/10-1/5 of the water area of the whole pool, and the temporary river crab fry rearing area can be surrounded by polyethylene mesh cloth, when river crab fries are reared, the temporary river crab fry rearing area is firstly cultivated, the rest part of the temporary river crab fry rearing area is used for nursing waterweeds, and after the waterweeds in the nursing area gradually recover and grow rapidly, the mesh cage of the temporary river crab fry rearing area is removed. The aquatic weed species planted mainly comprises hydrilla verticillata, eel grass, elodea nutans and the like, and the hydrilla verticillata and the elodea nutans are the best and the eel grass is the second time. The bitter herbs are mainly sowed, and the seed consumption is 0.1 kg/667 m²(ii) a The hydrilla verticillata and the elodea nutans are mainly subjected to asexual propagation, and a method of cutting stems, segmenting, skewering and inserting is adopted, wherein the using amount is 25-30 kg/667 m². The aquatic weeds are planted before the crabs are put into the pond, the planting time is generally about the clearness, the aquatic weeds grow before the crabs are put into the pond, otherwise, tender buds of the aquatic weeds are ingested by river crabs to influence the growth of the aquatic weeds.

Referring to fig. 1 and 2, a nano-microporous oxygen increasing pipeline 18 is laid in the adult crab culture pond, and is connected with a main ventilation pipe 16 through a reducer union, a roots blower (not shown) is connected with the main ventilation pipe 16, and a PVC plastic pipe with the diameter of 50mm can be used as the main ventilation pipe; the nano microporous oxygen increasing pipelines are installed at intervals of 8m, and are fixed at the positions 10-15 cm away from the bottom of the pool through bamboo piles. So, directly defeated the pond bottom to the oxygen-containing air through the fan, make nanometer micropore oxygenation pipeline from the bottom of the pool up aeration, form the atomizing bubble flow of a "V" type, from the bottom of the pool up to the water gas supply oxygen that looses, make each water layer dissolved oxygen volume improve fast in step, have oxidation and release to some poisonous and harmful gas that the bottom of the pool accumulated simultaneously. Normally, the fan is at night 22: starting the machine at about 00 hours, and stopping the machine after the sun comes out on the next day; in a preferred embodiment, a timer can be arranged on the aerator, and the aerator can automatically aerate according to the set time; in continuous rainy days and high-temperature seasons, the starting time needs to be properly advanced and prolonged, and oxygen needs to be increased in the daytime.

The aeration pipes 19 are arranged on two sides of the aeration main pipe and vertically enter the pond, so that the upper, middle and lower water bodies are oxygenated simultaneously, and the dissolved oxygen is ensured to be more uniform. Generally speaking, 2-3 sets of oxygenation facilities can be installed in parallel in a pond with about 15 mu, and Roots blowers with proper power are reasonably selected and installed according to the area of the pond. In a preferred embodiment, the aeration device adopts shunt control, energy conservation and synergy, and one oxygen increasing facility or all the oxygen increasing facilities can be selected to be started according to the dissolved oxygen condition. In another preferred embodiment, the culture system is provided with an online water quality monitoring system, the dissolved oxygen in the pond is monitored online in real time, and when the dissolved oxygen is lower than a set value, such as 5.5mg/L, a warning is given out, and the aerator is automatically or remotely turned on/off.

The aquaculture system also comprises a matched escape-proof facility, the periphery of the pond is enclosed by a polyethylene net sheet with the aperture of 5.35mm, the bottom of the net is buried in the soil by 10cm, and the height of the net is 1 m. At the inner side of the polyethylene mesh at certain intervals, for example, at the interval of 1 meter, the escape-proof wall is made of materials such as aluminum sheets or plastic films, is 0.5-0.6 m high, is buried in the soil by 10cm and slightly inclines towards the inner side of the pool; the corner of the escape-proof wall is arc-shaped.

The diagonal angle of the aquaculture pond is provided with a water inlet and a water outlet for timely regulating and controlling the water level in the pond, the water level regulation and control adhere to the principle of 'shallow front, medium depth and logistics', the water temperature is low in 4 months, the low water level is kept, the growth of aquatic weeds and the improvement of the water temperature are promoted, and the shelling of river crabs is promoted; the deep water level is kept in the middle period, particularly in hot summer, and the water is added and changed frequently in the later period, so that the water quality is kept fresh and the dissolved oxygen is sufficient. Usually, water is changed for 1 time every 3-4 days, water is changed for 1 time in 7-l 0 days when the water temperature is low, water is changed every day when the weather is hot, particularly, water is changed in time when river crabs are found to be different from the past when going to the bank and climbing nets, and the water change amount of each time generally accounts for about 1/5 of the total pool water amount. The water depth of the early stage is 0.5-0.6 m, the water depth of the middle stage is 1-1.2 m, and the water depth of the later stage is about 0.8 m.

According to the river crab culture system, the river crab culture method based on the river crab culture system comprises the following steps of:

crab larva selection: the young Chinese mitten crabs in the Yangtze river system are selected as crab seeds, and the requirements are that the body color is normal, the color is bright, the specification is uniform, the body is strong, the crawling is quick, the appendages are complete, the knuckles are not damaged, the liver is golden and glossy, the gill threads are white, and no parasites are attached. When stocking, soaking and washing the seeds for 3 to 5 minutes by using a 3 to 4 percent salt solution, or soaking the seeds for 20 to 30 minutes by using potassium permanganate with the concentration of 15 to 20 milligrams per liter; the male-female ratio is 3: 1 or so;

water treatment before cultivation: 100 g/m of 1000 square meters of water²The purifying agent is a solid-liquid mixture and comprises 16 to 26 parts by weight of magnesium hydroxide, 5 to 10 parts by weight of sodium hydrogen phosphate and 20 to 50 parts by weight of water; the pH value of the purifying agent is 9.5-10.5, and the purifying agent can well regulate a farm or a river with a small pH value, so that the water quality in the farm or the river returns to the alkalescent good pH valueThe ecological water treatment system is beneficial to the healthy circulation of water ecology and improves the environment of a river channel and a farm. The magnesium hydroxide accounts for 10-70% of the mass content and is the main component in the purifying agent, the magnesium hydroxide has extremely strong buffering performance and adsorption capacity, can be used for neutralizing various acid substances, and the pH value of the magnesium hydroxide cannot exceed 9 even if the magnesium hydroxide is excessive. In aquaculture farms and riverways, eleven common problems of peculiar smell caused by hydrogen sulfide and other sulfur-containing organic compounds generated by long-term accumulated sludge II are solved, magnesium hydroxide and sulfide can be used for generating magnesium sulfate, and the product magnesium sulfate is dissolved in water without any harm. The method for removing the hydrogen sulfide in the water body by using the magnesium hydroxide is an implementation scheme which has the advantages of easily obtained resources, environmental friendliness, economy, reasonability and simple operation.

Culturing the crabs: planting hydrilla verticillata and elodea nutans in the crab seedling culture pond, and transplanting water peanuts on the water surface, wherein the coverage surface accounts for 30-50% of the water surface; adding fresh water by 10cm 15 days before the crab seedlings are put into the pond; stocking the crab seedlings in a temporary stocking area, stocking the temporary stocking area to the breeding area after aquatic weeds grow out, and stocking 1-1.5 kg of crab seedlings per mu in ten days after 5 months;

aquatic plant cultivation and feed feeding: the main feed is water grass such as duckweed, and the like, and the secondary feed is wheat bran, bean dregs, compound feed and small trash fish; the daily feeding amount of the commercial feed is generally 2-3% of the weight of the juvenile crabs stored in the pond, and the feed is fed along the sides of the pond or shallow water at multiple points; the hydrilla verticillata and the elodea nutans are cultivated in a dot mode instead of strip cultivation, the distance between cultivation points is 80-100 cm, and the coverage area of the hydrilla verticillata and the elodea nutans respectively accounts for 20% of the water surface. When the water surface coverage rate in the elodea pond is reduced to below 20%, planting alternanthera philoxeroides into the pond, and washing and disinfecting the alternanthera philoxeroides with water before the alternanthera philoxeroides are placed into the pond; the coverage rate of the water surface of the peanuts in the pond is not more than 20%, and the coverage rate of the aquatic weeds in the pond is 60-65%. The growth of the waterweeds is rapid from the middle of 4 months to the last of 6 months, and the water surface coverage rate gradually rises from 20 percent to 40 percent; the water surface coverage rate gradually falls from 40% to below 20% from the first 7 th to the last 9 th. The method is characterized in that the growth of the elodea nutans is rapid from the middle ten days of 4 months to the last ten days of 5 months, the dissolved oxygen in water consumed at night is increased, the perishable parts at the upper ends of the elodea nutans need to be cut off in time, and the length of the elodea nutans is maintained at 20-40 cm and does not expose out of the water surface. When removing the excess aquatic weeds, the crab seedlings are prevented from being damaged. Crab pool seven-month waterPeanuts grow vigorously and need to be treated in time, so that the water surface coverage rate of the peanuts is guaranteed to be 40-50%, the water surface coverage rate of hydrilla verticillata and elodea nutans is lower than 20%, and the dissolved oxygen level of the aquaculture water body is improved; before Qingming, 200 kg of sterilized fresh spiral shell is put in per 667m²Uniformly throwing the snail in the whole pool, and feeding the snail once again according to the pool storage quantity of the snail in the crab pool in 7-8 months, wherein the feeding quantity is about 150 kg/667 m²(ii) a And applying biological fertilizer and organic fertilizer at proper time. In the early stage, bean cake, wheat flour, silkworm chrysalis meal, fish meal or minced small fish, crushed snail and clam meat are used as raw materials and mixed into granules for feeding, or open type compound feed is used as main feed for feeding. The middle stage mainly comprises fine and green feeds such as bean cake, corn, wheat, potato, pumpkin, sweet potato, etc. The proportion of animal baits (the animal baits account for about 50 percent) is properly increased in the later period or the special compound feed for the later period of the river crabs is fed. Before the exuviation of the river crabs comes, special compound feed with palatability or animal bait is fed, the proportion of the animal bait accounts for more than 2/3 of the total feeding amount, the exuviation auxin of the shrimps and the crabs is increased, and no single feed is fed, so that the exuviation of the river crabs has sufficient nutrition. Some water plants in the molting area are less, aquatic plants such as alternanthera philoxeroides and the like need to be put in time to provide places for the molting of the river crabs so as to ensure that the molting of the river crabs has good ecological environment.

Putting a calcium supplement: putting a calcium supplement once in a period of 10-15 days before river crab shelling; the calcium supplement is a solid-liquid mixture, and comprises the following components in parts by weight: 16-26 parts of calcium nitrate, 5-10 parts of zeolite powder and 20-50 parts of water; the pH value of the calcium supplement is 7.3-8.3; calcium is an important component of bones, scales, shells and the like of aquaculture species, the shelling time of shellfish aquatic products such as shrimps and crabs is prolonged, the shell hardening speed is reduced, and the shelling death phenomenon occurs under the condition of calcium deficiency, and the situations can be avoided by timely calcium supplement. The calcium nitrate is dissolved in water, but the calcium nitrate is toxic and can not be directly eaten, and the calcium nitrate is converted into purer calcium carbonate which can be eaten and plays a role in calcium supplement; if the calcium nitrate solution is added into the sodium carbonate solution, calcium carbonate precipitation can be obtained, and the calcium carbonate precipitation can be eaten by shrimps and crabs in a farm to supplement calcium. The zeolite powder is prepared by grinding natural zeolite rock, is light green and white in color, can remove 95% of ammonia nitrogen in water, purify water and relieve the phenomenon of water transfer; the zeolite has various basic conditions of being used as a carrier and a diluent of the additive premix, the neutral pH of the zeolite is between 7 and 7.5, the surface of the zeolite is rough and has a porous structure, so that the zeolite has stronger carrying capacity, the material can be uniformly adsorbed on the surface and can be adsorbed in holes and channels, the availability of the material is improved, and the uniformity of mixing is also greatly improved; meanwhile, the release time of the trace components can be properly prolonged, the absorption of animals is facilitated, and the growth promoting effect is obvious. In a preferred embodiment, the calcium supplement can be added for 1 more time during the river crab shelling period.

Water quality monitoring and oxygenation: controlling the working switch and working time of the oxygen increasing device according to the water quality monitoring data; ensuring the oxygen content of the water body; the quicklime is used for water quality adjustment, the quicklime is generally used once every 10-15 days, the concentration of the quicklime used each time is 10-15 ppm, and the method mainly improves the ph value and increases the content of calcium in a water body. The application of the calcium dihydrogen phosphate which is easily dissolved in water is matched, so that the water quality can be adjusted, and the river crabs can be directly absorbed through gill skin and gastrointestinal inner wall, so that the molting speed of the river crabs can be correspondingly increased, and the growth of the river crabs is promoted. Generally 1 time per month, 2 kg/667 m per administration²The calcium carbonate is used in a crossed way with the quicklime;

biological agent regulation: applying water-regulating biological agents such as photosynthetic bacteria, bacillus, lactic acid bacteria, bifidobacteria, actinomycetes, saccharomycetes (EM), mineral substances and the like from 4 months, starting up for oxygenation at noon in sunny days in the middle and later periods of cultivation for 2-3 hours, and starting up for oxygenation at night in rainy days; spraying bottom-modified biological preparations such as EM bacteria, high molecular organic polymers, oxygen increasing agents, synergistic agents and the like once every 15 days from the beginning of 6 months;

water level monitoring and adjusting: according to the water level monitoring result, adjusting the water level of the aquaculture pond in time; ensuring the water depths in different periods according to the period of river crab culture; for the mouth of an old culture pond, 2-2.5 kg of calcium superphosphate is applied per mu and water is splashed into the whole pond due to the fact that the pond bottom is relatively fertile; splashing quicklime every 15-20 days, and each 667m²The dosage is 10 kg; the depth of the pool water is stabilized at 1-1.5 m, and photosynthetic bacteria are splashed regularly;

stress prevention and control: the principle of 'prevention is taken as the main part and prevention and cure are combined' is followed, and ecological regulation and scientific medication are insisted on being combined. And (4) well disinfecting, namely clearing and disinfecting the pond, disinfecting crab bodies, and disinfecting baits and food farms. During the fishing and transportation process, the operation is carried out as carefully as possible, so as to avoid the damage of the crab body. The variety proportion and the breeding specification are reasonably matched, high-quality baits are selected, the bait deterioration pollution is avoided, and the fresh baits which are palatable in each growth stage of the river crabs are ensured. During the river crab shelling period, fresh water is changed frequently, and micro-flowing water is kept to stimulate the shelling of the river crabs. The prevention work is done in advance in the epidemic season of the crabs, during the culture period, a substrate modifier and a microecological preparation are used for improving the substrate and regulating the water quality, a small amount of quick lime is used for multiple times at regular intervals, an aerator is started timely, the application of the microecological preparation is emphasized, the water quality and the substrate are improved, the granular feed is sprayed with the dissolved water of the biological preparation for feeding all the year around, and VC and poly-vitamin polysaccharide are added into the feed at regular intervals to improve the immunity of the river crabs. In 4-5 months, ciliate is killed once by using ciliate-killing agent such as ciliate-killing agent, carapace-killing agent, ciliate-killing agent or zinc sulfate compound drug (used 7 days before molting). After the yellow plum is finished and before the high temperature comes, water body disinfection and internal medicine bait taking are carried out for 3 days continuously. In 9 middle of the month, ciliates are killed once, and water disinfection and internal medicine bait are carried out.

In a preferred embodiment, a mixed culture mode can be adopted, such as:

1. polyculture of river crab and mandarin fish

The water space and natural baits are fully utilized, the problems of food competition, dissolved oxygen competition, water body competition and the like between wild fishes and river crabs are solved, the culture yield of a unit area for river crab culture is increased under the condition that only the mandarin fish seed investment is increased without increasing baits, other production cost and management cost, the conversion of low-quality fishes to high-quality fishes is realized, and the economic comprehensive benefit of river crab culture is improved. Selecting large-sized self-breeding crabs with the specification of 120-140 crabs per kilogram and the stocking density of 600 crabs per 667m². Stocking 5-7 cm mandarin fish seeds 20-50/667 in ten days in the middle of 6 monthsm². The bait fish is fed to the mandarin fish once before the mandarin fish is put into the pond, the tail number of the mandarin fish is generally 4-5 times of that of the mandarin fish, and after 15 days, the mandarin fish is fed normally after the bait fish is left about 20%.

2. River crab and crayfish polyculture

The crayfish is basically similar to the river crab in habit, feeding property and activity space, and meanwhile, the crayfish and the river crab are mixed and cultured in the same pond, so that the culture resources can be utilized to the maximum extent, the culture yield of the river crab culture unit area is increased, and the economic and comprehensive benefits of the river crab culture are improved. Selecting large-sized self-breeding crabs with the specification of 120-140 crabs per kilogram and the stocking density of 600 crabs per 667m². The crayfish is 200-400/kg in specification, and 2500-3000 crayfish are placed per mu. The silver carp is 11 fish/kg per mu, and 10 fish per mu. Putting the crabs into the circular ditches for temporary culture in 3 months later, putting the crabs into a pond after the transplanted aquatic weeds survive, simultaneously breeding chub seeds, and putting crayfish larvae in 4 months later.

3. Polyculture of river crab and freshwater shrimp

The area and the bait of the pond are fully utilized, the river crabs and the freshwater shrimps do not influence each other, a certain promoting effect is achieved, the comprehensive production capacity of the pond can be effectively improved, the investment of seedlings and feeds is properly increased, and better economic benefits can be obtained compared with singly breeding the river crabs or the freshwater shrimps. Selecting large-sized self-breeding crabs with the specification of 120-140 crabs per kilogram and the stocking density of 600 crabs per 667m². Laying the ovigerous shrimps in the middle and last ten days of 5 months, selecting high-quality shrimps with yellow-green egg granules, no damage and 4-6 cm average specification, and stocking 3 kg/667 m²Left and right. Putting parent shrimps into the pond for 2-3 days, and using 1-3 kg/667 m of bio-organic fertilizer²Cultivating water, soaking and grinding soybeans into pulp of 1 kg/667 m after the young shrimps are hatched for 3-5 days²The dregs are uniformly splashed along the side of the pond to promote the shrimps to quickly become into young shrimps.

By adopting the river crab culture system and the culture method, the quality of finished crabs is excellent, large-scale culture can be realized, the economic benefit is high, the core demonstration area is 1 ten thousand mu according to the culture mode, the average yield per mu is 80-100 kg, the specification of male crabs is more than 200 g, the specification of female crabs is more than 150 g and reaches 60%, the profit per mu of river crabs is more than 5000 yuan, the effect per mu is increased by 800 yuan, the culture diseases are reduced by more than 30%, the culture benefit is improved by more than 20%, the zero emission of tail water in the culture process is realized, the average occupancy rate of system resources is reduced by more than 30%, and 25 ten thousand mu is driven by radiation.

The present invention is not limited to the embodiments described above, and those skilled in the art may make modifications or changes within the scope of the disclosure without departing from the spirit of the present invention, so that the scope of the present invention is defined by the appended claims.

Claims

1. An improved river crab ecological breeding method comprises the following steps:

water level monitoring and adjusting: according to the water level monitoring result, adjusting the water level of the aquaculture pond in time; the depth of the pool water is stabilized at 1-1.5 m;

2. The improved ecological cultivation method of river crabs as claimed in claim 1, further comprising the step of polyculture of river crabs and mandarin fish, polyculture of river crabs and crayfish, or polyculture of river crabs and freshwater shrimps.

3. An improved ecological culture method of river crabs as claimed in claim 1 or 2, wherein the mass content of magnesium hydroxide in the purificant is 10 to 70 percent.

4. The improved ecological cultivation method of river crabs as claimed in claim 3, wherein the mass content of magnesium hydroxide in the purifying agent is 30% -70%.

5. The improved ecological culture method of river crabs as claimed in claim 1 or 2, wherein the calcium nitrate in the calcium supplement is contained in an amount of 10 to 70% by mass.

6. The improved ecological culture method of river crabs as claimed in claim 5, wherein the calcium nitrate in the calcium supplement agent is present in an amount of 20 to 50% by mass.

7. An improved ecological culture method for river crabs as claimed in claim 1 or 2, wherein the step of adding the calcium supplement further comprises adding the calcium supplement 1 time during the period of shelling of river crabs.