1 venue selection
1.1 Sufficient water supply and suitable water quality
As long as the water quality is suitable and the amount of water is abundant, crab farming can generally be used as a water source. If there is a nearby industrial wastewater discharge, attention must be paid to it. The water quality must be analyzed to see if there are any harmful substances to crabs. The key to water quality is the key point of control (ccp). Possible hazards include chemical pollution and biological pollution. The standards for wastewater in the aquaculture industry have been proposed by the WTO. These guidelines can be used as critical thresholds for water quality. According to China's "fishery water quality standards", "pollution of freshwater aquaculture water quality (NY5051--2001)" standard to determine whether the water quality is applicable. While fully collecting local hydrological, meteorological, topographic, and soil-related data, it is necessary to fully combine the seasonal crab production and injection and drainage measures to determine if the water supply is adequate.
1.2 Appropriate terrain and convenient transportation
Should not be one-sided pursuit of flat open and occupy fertile fields, as far as possible the use of factory-free, pollution-free lake banks to build a contiguous crab pollution-free breeding base. This terrain is in line with the principle of the development of pollution-free farming, which can make full use of the topography, achieve self-discharge and irrigation, and receive savings on investment, which can do more with less. The soil quality of the construction site should ensure that the bottom of the crab pool built on it does not leak water, and the excavated earth materials should be suitable for the construction of solid dykes without leakage. The location of the construction site should not be selected from a place far away from the transportation line in order to facilitate the transportation of aquaculture supplies and aquaculture products.
2 Pond construction
2.1 Area
Artificial breeding ponds should also choose a larger surface. Large area, large force, can automatically increase oxygen, is conducive to the convection of the upper and lower water layers, improve the dissolved oxygen conditions of the lower layer of water, and help the harmful gas in the bottom layer to escape in time, generally about 1 hectare of pond is more appropriate .
2.2 Water depth
Raising ponds of crabs requires a certain depth of water and water storage capacity, deep pool water, large water capacity, water temperature is not easy to change, water quality is relatively stable, and is not easily affected by drought, which is beneficial to the growth of crabs. However, the deep water in the pool is not suitable for the growth of crabs and aquatic plants. Practice has proved that it is appropriate to retain 0.5-1.5m water depth all year round. The facilities for irrigation and drainage of crab ponds should be perfected so that the high irrigation and low row, the row and the irrigation can be separated, and each crab pool can be filled with water, and the rows can be drawn, and the crabs can be avoided by drought and flood, and the stable yield and high yield can be achieved.
2.3 Terrain
The terrain is preferably rectangular in the east-west direction, which is conducive to feeding and management and the operation of pulling nets. The sunshine is long and windy.
2.4 Anti-escape
Crabs climb very quickly and have a strong ability to escape. Usually a reed, a branch or a small hole in a crab pond can be the passage for crabs to escape. There are often only a few “crab ladders†at the edge of the wall to facilitate the escape of other crabs. Therefore, it is necessary to have solid and reliable escape prevention equipment around the adult crab pool to prevent crabs from fleeing. Generally, cement anti-light walls, calcium plastic plates, iron sheets, nylon films, glass, oil felts, etc. are used to prevent flight.
3 stocking preparation
3.1 clear pond disinfection
In the crab ponds, pests such as wild fish, water snakes, water rats, aquatic insects, and various pathogens are frequently consumed. They not only consume dissolved oxygen in the water, but also attack crabs and compete for feed. Therefore, clearing ponds should be conducted. The commonly used Qingchi disinfection drugs mainly include quick lime, bleaching powder, and tea bream. Qingchi is generally conducted 10 to 15 days before the stocking of crabs. Clearing methods include dry clearing ponds and water clearing ponds. Such as using quicklime, dry clearing pond, the amount of 975-1125kg per hectare, after the dissolution of Quanchiposa. Lime clearing pool not only kills harmful organisms in the water, but also improves the bottom soil quality and increases the calcium content in the water. This plays an important role in the growth and development of crabs. In addition, weeds should be removed from the pool before clearing the pond, and excessive silt should be dug up to keep the crab pool clean.
3.2 Planting water plants
Aquatic grass is not only a place for crabs to inhabit and avoid the enemy's clam shells, but also has the effect of purifying water quality, and it is also a good feed for crabs to eat. After the disinfection in the clear pond, the pool water is maintained at 20--30cm until the temperature of the water gradually rises. After the drug in the clear pond has disappeared, the plants are planted.
3.2.1 aquatic species
There are submerged organisms such as Hymenocallis, Elodea, and Vallisneria. From the point of view of the quality of aquatic weeds, the best choices are black algae and Elodea, followed by bittergrass; from the point of view of the growing season, it is better to use Elodea, with spring and autumn as the best growing season, it can be planted as early as possible. Growth, so that early crabs can be released and fed and managed as soon as possible.
3.2.2 Planting methods
The black-leaf hyphae and Elodea are mainly vegetatively propagated, and cuttings of stems are cut into sections. The amount of grass used per hectare is 150--250 kg, and the row spacing is 1-1.5 m. The whole pond is planted; the bitter grass is a typical sink. Water plants, the seeds of which are small, soaked for 10 to 15 hours before the insertion of water, wipe out the grass seeds with a rubbing board, and mix the grass seeds with the soil and splash it. It can be sowed and drilled. 0.5 hectares per kilogram of seed are planted.
3.2.3 Planting time
The leaves were black algae and Vallisneria in March. Elodea is after the clear pond or early spring. Before planting aquatic plants, 30-45kg of compound fertilizer is applied as a base fertilizer per hectare, allowing it to grow rapidly.
3.2.4 Coverage
The water grass coverage can reach 30% - 35% to meet the living habits of crabs. For ponds with submerged plants, such as black-leaf algae and bittergrass, water-peeling belts with a width of 2m must be installed 1m away from the pool. The water peanut strips are set and are stocked after the crabs are stocked.
3.3 Release screw
Live snail meat tastes delicious, crabs like food, is an ideal high-quality natural feed. At the same time, snails mainly ingest plankton in the water, which can effectively reduce the plankton content in ponds, and play a role in purifying water quality, which is conducive to the growth of crabs. The price of snails is low and sources are wide, which can significantly reduce the cost of breeding and improve the economic benefits of breeding. From June to July, a large number of breeding snails were started. The snails are not only tender, but also rich in nutrition and high in utilization. The crabs prefer to eat. When putting snails in ponds, care should be taken to disinfect them. Strong chlorine can be used to kill bacteria and protozoa on snails, and snails should be washed when they are released. Generally, 2000--3000 kg of snails are put into each pond for feeding crabs.
4 Seed stocking
4.1 Selection of crab species
It is best to choose the crab species cultivated by the natural seedlings of the Yangtze River or the artificial breeding of crabs in the Yangtze River water system. The crab species should have complete specifications, robust physique, complete appendages, no disease, injury, and crawling activity. Agile, there are no attachments on the body. The same batch of crab species to be purchased should be placed in the same pond or fence.
4.2 Restocking methods
Strictly open the door for good. For the newly hatched juvenile crabs, if they adopt three-level stocking, they can be placed in large pools before and after spring; in secondary stocking, they can be stocked with crabs for more than 20 days, and the clam shells can be transferred to crab pools from crab ponds twice. Specifically: "One District," "Three Reforms," ​​and "Three Fitness." “One districtâ€, ie setting up a crab species holding area, using a net to surround a breeding area, which is 1/10---1/5 of the area of ​​Datang, puts high-quality crab species into them and strengthens cultivation, and waits for water plants in Datang. It grows to account for more than 50% of the entire surface of the pond, snails have been propagated for a certain amount and then released to people in Datang for feeding; “three changesâ€, that is, the winter release is changed to spring release, the small size is changed to the large size, and the outer crab is changed to self-climbing. The "Three Adaptations" are appropriate stocking specifications, appropriate stocking times, and appropriate stocking densities. Stocking specifications are generally controlled at 80-80 kg per kg, and the stocking time should be sooner rather than later, and more than 80% of the stocked crabs need to be self-breeding crabs. Production practices have shown that the survival rate, disease resistance, and maturity of self-fermented crab species are significantly better than those of out-deep crab species. Before stocking, crabs should be soaked with 6mg/L potassium permanganate solution for 10-15 minutes before being placed in the holding area.
4.3 Stocking Density
For ponds with sufficient water resources, abundant feed, and good husbandry and management, the stocking density is generally controlled at about 1/m2.
4.4 Stocking time
It is generally controlled from the end of February to March. The stocking of crabs should be selected when the weather is sunny and warm and the water temperature is high, so as to ensure the survival rate of stocking.
5 Feeding
Feed is the material basis for crab cultivation. On the one hand, the whole growing stage can use artificial grasses and other feed organisms cultivated in ponds. On the other hand, most of the feed needs artificial feeding.
5.1 Feed Sources
Mainly from two aspects: first, the cultivation of basic feed such as water grass and snail, and second, artificial feed. The planting coverage of aquatic plants is generally around 70%. Before and after Ching Ming, snails are fed with about 4500kg per hectare, and once in August, they are replenished once with 1500kg per hectare. For artificial feeding, artificial feeding management is conducted according to scientific feeding principles of “preliminarily refined, middle-greenâ€, “combination of meat and vegetarian dishes, and combination of green tea†and scientific feeding methods of “four settings†and “four viewsâ€. Before and after the animal feed and crab pellet feed. In the medium term, plant-based feeds, aquatic plants and pumpkins are the main products. Insist that you don't feed deteriorating feeds, and timely fish out residues and feeds.
5.2 Scientific Feeding
First of all pay attention to feed quality. It is required to use full-priced feed instead of fresh feed. Compound feed requires comprehensive nutrition, low cost, low feed coefficient, easy use, good food intake, and no pollution to water quality. Secondly, pay attention to the feeding site. Feeding sites should be appropriate, not too much nor too little. Disinfect the feeding sites frequently. The third is to determine a reasonable feeding time and frequency. In the evening, vote for more. In general, a small number of feeding methods are worth promoting. The number of feedings can be appropriately reduced in the outbreak season. Fourth, we must determine a reasonable amount of feed. It is determined according to different specifications, different breeding seasons, different climates, different environmental conditions and farming conditions. Be careful not to eat too much crabs, and do not make them affect the growth due to insufficient food intake. In the outbreak of the disease, we must appropriately reduce the amount of feeding, usually about 80%.
6 Disease Prevention and Control
6.1 Adjusting water quality
The "three adjustments" measures should be taken during the entire cultivation period. Renewing: Injecting new water, 5-7 days of water injection, 10-15 days of water replacement, hot water injection of 6-9 cm per day, 315 days of water-times. Tuning: The pH is adjusted to control the pH between 7.5-8.5. Quicklime is used once every 10-15 days, and the amount is 150kg per m2 per hectare of water body. This not only increases the pH value, but also increases the concentration of calcium ions in the water to supply the crabs for absorption. Reassignment: The application of photosynthetic bacteria to revitalize the body of water, 75-90 kg per hectare, once every half months, mixed with soil or dilute Quanchiposa with water. Through these three adjustments, the specific requirements of dissolved oxygen to maintain at 5mg / L or more, more than 40cm transparency, pH value of 7.5 or more, truly "clean, new, tender, cool" purpose. While regulating the water quality, it is also necessary to regulate the water level in accordance with the three phases of “pre-shallow, medium-deep, and post-stableâ€. From March to May, the water depth is controlled at 0.5--0.6m, during June-August, it is controlled at 1.2--1.5m, and from September to October, it is stable at about 1m. During the high temperature season, the water level should be deepened, so that the water temperature is too high and the river crab is affected. Shell growth.
6.2 Strengthen Disease Prevention
Prevention and control of river crab diseases must follow the principle of “prevention first, prevention and control combinedâ€, adhere to the principle of ecological prevention, supplemented by drug control, and vigorously promote the ecological cultivation techniques of river crabs to achieve the objective of avoiding illness or illness, and avoiding drugs or drugs. . That is, the use of drugs that are highly effective, low in toxicity, have no side effects, or have little side effects are used for assisted prevention and treatment. The main drugs used are lime, chlorine dioxide, strong chlorine, zinc sulfate, Chinese herbal medicine and so on. Dosage standard: quicklime 1O --- 15kg per hectare, water sprinkling; chlorine dioxide 3kg per hectare, sprinkling of sprinkling; zinc sulfate 0.2g/m3, sprinkling of water (all 1m water depth usage). Chinese herbal medicine added 1-1.5kg per 100kg of feed, made into medicine and fed for 5-7 days. Control methods: First, the combination of treatment and pest control (after the first pest treatment), the second is the combination of oral administration and external use, the third is the combination of western medicine and traditional Chinese medicine, the fourth is the cross-use of different drugs, and the fifth is the use of drug prevention in advance. Planting aquatic plants and transplanting snails are two key technologies for improving water bodies and improving sediment quality. The application of photosynthetic bacteria to control harmful bacteria has obvious growth and reproduction effects.
7 day-to-day management
7.1 Daily work
Including "six checks, six diligence", that is, checking whether the crab activities are normal and diligent in patrol ponds, insisting on patrol pools in the morning, middle and evening; checking whether the crab body is deprived of oxygen and doing the sanitation work to improve water quality. Check whether there are predator creatures in the pond, and remove the enemy's harmful creatures. Check if there are soft shell crabs in the crab ponds, and protect the soft shell crabs. You can cast more palatable animal feed to restore the stamina as soon as possible. The ability to defend against predators; to check if crabs are sick, to prevent and treat crabs; to check and prevent the escape facilities of crab ponds, and to maintain them. In addition, in daily work, be sure to keep the crab pool environment quiet and comfortable, do not interfere too much with the crab feeding, oyster shell process, feed, clean the food field to light, in order to improve the survival rate of shell crab. At the same time, we must do a good job in keeping a record of the culture ponds.
7.2 Routine detection
Regularly test the biological characteristics of the cultured crabs, aquaculture hydration indicators, and make records. Content includes: collection, processing and preservation of water samples. General sampling should be able to represent the comprehensiveness of crab pond waters, preferably in the morning; the number of sampling times can be determined according to needs; sampling depth should be based on water depth conditions, a layer is collected at certain intervals, and cryogenic preservation is adopted. The analysis of fishery water quality should mainly consider physicochemical factors that are most closely related to crab culture. The conventional standard analysis method is the main method for the current water quality analysis.
8 Crab fishing
8.1 Fishing time
When the proportion of mature crabs in the gonads accounts for 80% of crabs, fishing is usually done in October.
8.2 Fishing methods
There are mainly three kinds of fishing methods, such as ground cage fishing, water fishing, and silicon fishing. Among them: the cage fishing method is the most practical fishing method. Water fishing method: In the water inlet, a fishing net type fishing gear is opened, and the water outlet is opened so that the water flows, and the crab crawls into the water with the water. Pay attention to two points: one point is that one discharge of water is inexhaustible, and the pool water should be added to the depth of 0.2---0.3m, then the water should be added, and then the water should be discharged again. This is repeated several times; the other point is that after the pool water is discharged, the river crabs are all out. In the evening, climb up the bank to the edge of the escape wall, which can be captured manually.
1.1 Sufficient water supply and suitable water quality
As long as the water quality is suitable and the amount of water is abundant, crab farming can generally be used as a water source. If there is a nearby industrial wastewater discharge, attention must be paid to it. The water quality must be analyzed to see if there are any harmful substances to crabs. The key to water quality is the key point of control (ccp). Possible hazards include chemical pollution and biological pollution. The standards for wastewater in the aquaculture industry have been proposed by the WTO. These guidelines can be used as critical thresholds for water quality. According to China's "fishery water quality standards", "pollution of freshwater aquaculture water quality (NY5051--2001)" standard to determine whether the water quality is applicable. While fully collecting local hydrological, meteorological, topographic, and soil-related data, it is necessary to fully combine the seasonal crab production and injection and drainage measures to determine if the water supply is adequate.
1.2 Appropriate terrain and convenient transportation
Should not be one-sided pursuit of flat open and occupy fertile fields, as far as possible the use of factory-free, pollution-free lake banks to build a contiguous crab pollution-free breeding base. This terrain is in line with the principle of the development of pollution-free farming, which can make full use of the topography, achieve self-discharge and irrigation, and receive savings on investment, which can do more with less. The soil quality of the construction site should ensure that the bottom of the crab pool built on it does not leak water, and the excavated earth materials should be suitable for the construction of solid dykes without leakage. The location of the construction site should not be selected from a place far away from the transportation line in order to facilitate the transportation of aquaculture supplies and aquaculture products.
2 Pond construction
2.1 Area
Artificial breeding ponds should also choose a larger surface. Large area, large force, can automatically increase oxygen, is conducive to the convection of the upper and lower water layers, improve the dissolved oxygen conditions of the lower layer of water, and help the harmful gas in the bottom layer to escape in time, generally about 1 hectare of pond is more appropriate .
2.2 Water depth
Raising ponds of crabs requires a certain depth of water and water storage capacity, deep pool water, large water capacity, water temperature is not easy to change, water quality is relatively stable, and is not easily affected by drought, which is beneficial to the growth of crabs. However, the deep water in the pool is not suitable for the growth of crabs and aquatic plants. Practice has proved that it is appropriate to retain 0.5-1.5m water depth all year round. The facilities for irrigation and drainage of crab ponds should be perfected so that the high irrigation and low row, the row and the irrigation can be separated, and each crab pool can be filled with water, and the rows can be drawn, and the crabs can be avoided by drought and flood, and the stable yield and high yield can be achieved.
2.3 Terrain
The terrain is preferably rectangular in the east-west direction, which is conducive to feeding and management and the operation of pulling nets. The sunshine is long and windy.
2.4 Anti-escape
Crabs climb very quickly and have a strong ability to escape. Usually a reed, a branch or a small hole in a crab pond can be the passage for crabs to escape. There are often only a few “crab ladders†at the edge of the wall to facilitate the escape of other crabs. Therefore, it is necessary to have solid and reliable escape prevention equipment around the adult crab pool to prevent crabs from fleeing. Generally, cement anti-light walls, calcium plastic plates, iron sheets, nylon films, glass, oil felts, etc. are used to prevent flight.
3 stocking preparation
3.1 clear pond disinfection
In the crab ponds, pests such as wild fish, water snakes, water rats, aquatic insects, and various pathogens are frequently consumed. They not only consume dissolved oxygen in the water, but also attack crabs and compete for feed. Therefore, clearing ponds should be conducted. The commonly used Qingchi disinfection drugs mainly include quick lime, bleaching powder, and tea bream. Qingchi is generally conducted 10 to 15 days before the stocking of crabs. Clearing methods include dry clearing ponds and water clearing ponds. Such as using quicklime, dry clearing pond, the amount of 975-1125kg per hectare, after the dissolution of Quanchiposa. Lime clearing pool not only kills harmful organisms in the water, but also improves the bottom soil quality and increases the calcium content in the water. This plays an important role in the growth and development of crabs. In addition, weeds should be removed from the pool before clearing the pond, and excessive silt should be dug up to keep the crab pool clean.
3.2 Planting water plants
Aquatic grass is not only a place for crabs to inhabit and avoid the enemy's clam shells, but also has the effect of purifying water quality, and it is also a good feed for crabs to eat. After the disinfection in the clear pond, the pool water is maintained at 20--30cm until the temperature of the water gradually rises. After the drug in the clear pond has disappeared, the plants are planted.
3.2.1 aquatic species
There are submerged organisms such as Hymenocallis, Elodea, and Vallisneria. From the point of view of the quality of aquatic weeds, the best choices are black algae and Elodea, followed by bittergrass; from the point of view of the growing season, it is better to use Elodea, with spring and autumn as the best growing season, it can be planted as early as possible. Growth, so that early crabs can be released and fed and managed as soon as possible.
3.2.2 Planting methods
The black-leaf hyphae and Elodea are mainly vegetatively propagated, and cuttings of stems are cut into sections. The amount of grass used per hectare is 150--250 kg, and the row spacing is 1-1.5 m. The whole pond is planted; the bitter grass is a typical sink. Water plants, the seeds of which are small, soaked for 10 to 15 hours before the insertion of water, wipe out the grass seeds with a rubbing board, and mix the grass seeds with the soil and splash it. It can be sowed and drilled. 0.5 hectares per kilogram of seed are planted.
3.2.3 Planting time
The leaves were black algae and Vallisneria in March. Elodea is after the clear pond or early spring. Before planting aquatic plants, 30-45kg of compound fertilizer is applied as a base fertilizer per hectare, allowing it to grow rapidly.
3.2.4 Coverage
The water grass coverage can reach 30% - 35% to meet the living habits of crabs. For ponds with submerged plants, such as black-leaf algae and bittergrass, water-peeling belts with a width of 2m must be installed 1m away from the pool. The water peanut strips are set and are stocked after the crabs are stocked.
3.3 Release screw
Live snail meat tastes delicious, crabs like food, is an ideal high-quality natural feed. At the same time, snails mainly ingest plankton in the water, which can effectively reduce the plankton content in ponds, and play a role in purifying water quality, which is conducive to the growth of crabs. The price of snails is low and sources are wide, which can significantly reduce the cost of breeding and improve the economic benefits of breeding. From June to July, a large number of breeding snails were started. The snails are not only tender, but also rich in nutrition and high in utilization. The crabs prefer to eat. When putting snails in ponds, care should be taken to disinfect them. Strong chlorine can be used to kill bacteria and protozoa on snails, and snails should be washed when they are released. Generally, 2000--3000 kg of snails are put into each pond for feeding crabs.
4 Seed stocking
4.1 Selection of crab species
It is best to choose the crab species cultivated by the natural seedlings of the Yangtze River or the artificial breeding of crabs in the Yangtze River water system. The crab species should have complete specifications, robust physique, complete appendages, no disease, injury, and crawling activity. Agile, there are no attachments on the body. The same batch of crab species to be purchased should be placed in the same pond or fence.
4.2 Restocking methods
Strictly open the door for good. For the newly hatched juvenile crabs, if they adopt three-level stocking, they can be placed in large pools before and after spring; in secondary stocking, they can be stocked with crabs for more than 20 days, and the clam shells can be transferred to crab pools from crab ponds twice. Specifically: "One District," "Three Reforms," ​​and "Three Fitness." “One districtâ€, ie setting up a crab species holding area, using a net to surround a breeding area, which is 1/10---1/5 of the area of ​​Datang, puts high-quality crab species into them and strengthens cultivation, and waits for water plants in Datang. It grows to account for more than 50% of the entire surface of the pond, snails have been propagated for a certain amount and then released to people in Datang for feeding; “three changesâ€, that is, the winter release is changed to spring release, the small size is changed to the large size, and the outer crab is changed to self-climbing. The "Three Adaptations" are appropriate stocking specifications, appropriate stocking times, and appropriate stocking densities. Stocking specifications are generally controlled at 80-80 kg per kg, and the stocking time should be sooner rather than later, and more than 80% of the stocked crabs need to be self-breeding crabs. Production practices have shown that the survival rate, disease resistance, and maturity of self-fermented crab species are significantly better than those of out-deep crab species. Before stocking, crabs should be soaked with 6mg/L potassium permanganate solution for 10-15 minutes before being placed in the holding area.
4.3 Stocking Density
For ponds with sufficient water resources, abundant feed, and good husbandry and management, the stocking density is generally controlled at about 1/m2.
4.4 Stocking time
It is generally controlled from the end of February to March. The stocking of crabs should be selected when the weather is sunny and warm and the water temperature is high, so as to ensure the survival rate of stocking.
5 Feeding
Feed is the material basis for crab cultivation. On the one hand, the whole growing stage can use artificial grasses and other feed organisms cultivated in ponds. On the other hand, most of the feed needs artificial feeding.
5.1 Feed Sources
Mainly from two aspects: first, the cultivation of basic feed such as water grass and snail, and second, artificial feed. The planting coverage of aquatic plants is generally around 70%. Before and after Ching Ming, snails are fed with about 4500kg per hectare, and once in August, they are replenished once with 1500kg per hectare. For artificial feeding, artificial feeding management is conducted according to scientific feeding principles of “preliminarily refined, middle-greenâ€, “combination of meat and vegetarian dishes, and combination of green tea†and scientific feeding methods of “four settings†and “four viewsâ€. Before and after the animal feed and crab pellet feed. In the medium term, plant-based feeds, aquatic plants and pumpkins are the main products. Insist that you don't feed deteriorating feeds, and timely fish out residues and feeds.
5.2 Scientific Feeding
First of all pay attention to feed quality. It is required to use full-priced feed instead of fresh feed. Compound feed requires comprehensive nutrition, low cost, low feed coefficient, easy use, good food intake, and no pollution to water quality. Secondly, pay attention to the feeding site. Feeding sites should be appropriate, not too much nor too little. Disinfect the feeding sites frequently. The third is to determine a reasonable feeding time and frequency. In the evening, vote for more. In general, a small number of feeding methods are worth promoting. The number of feedings can be appropriately reduced in the outbreak season. Fourth, we must determine a reasonable amount of feed. It is determined according to different specifications, different breeding seasons, different climates, different environmental conditions and farming conditions. Be careful not to eat too much crabs, and do not make them affect the growth due to insufficient food intake. In the outbreak of the disease, we must appropriately reduce the amount of feeding, usually about 80%.
6 Disease Prevention and Control
6.1 Adjusting water quality
The "three adjustments" measures should be taken during the entire cultivation period. Renewing: Injecting new water, 5-7 days of water injection, 10-15 days of water replacement, hot water injection of 6-9 cm per day, 315 days of water-times. Tuning: The pH is adjusted to control the pH between 7.5-8.5. Quicklime is used once every 10-15 days, and the amount is 150kg per m2 per hectare of water body. This not only increases the pH value, but also increases the concentration of calcium ions in the water to supply the crabs for absorption. Reassignment: The application of photosynthetic bacteria to revitalize the body of water, 75-90 kg per hectare, once every half months, mixed with soil or dilute Quanchiposa with water. Through these three adjustments, the specific requirements of dissolved oxygen to maintain at 5mg / L or more, more than 40cm transparency, pH value of 7.5 or more, truly "clean, new, tender, cool" purpose. While regulating the water quality, it is also necessary to regulate the water level in accordance with the three phases of “pre-shallow, medium-deep, and post-stableâ€. From March to May, the water depth is controlled at 0.5--0.6m, during June-August, it is controlled at 1.2--1.5m, and from September to October, it is stable at about 1m. During the high temperature season, the water level should be deepened, so that the water temperature is too high and the river crab is affected. Shell growth.
6.2 Strengthen Disease Prevention
Prevention and control of river crab diseases must follow the principle of “prevention first, prevention and control combinedâ€, adhere to the principle of ecological prevention, supplemented by drug control, and vigorously promote the ecological cultivation techniques of river crabs to achieve the objective of avoiding illness or illness, and avoiding drugs or drugs. . That is, the use of drugs that are highly effective, low in toxicity, have no side effects, or have little side effects are used for assisted prevention and treatment. The main drugs used are lime, chlorine dioxide, strong chlorine, zinc sulfate, Chinese herbal medicine and so on. Dosage standard: quicklime 1O --- 15kg per hectare, water sprinkling; chlorine dioxide 3kg per hectare, sprinkling of sprinkling; zinc sulfate 0.2g/m3, sprinkling of water (all 1m water depth usage). Chinese herbal medicine added 1-1.5kg per 100kg of feed, made into medicine and fed for 5-7 days. Control methods: First, the combination of treatment and pest control (after the first pest treatment), the second is the combination of oral administration and external use, the third is the combination of western medicine and traditional Chinese medicine, the fourth is the cross-use of different drugs, and the fifth is the use of drug prevention in advance. Planting aquatic plants and transplanting snails are two key technologies for improving water bodies and improving sediment quality. The application of photosynthetic bacteria to control harmful bacteria has obvious growth and reproduction effects.
7 day-to-day management
7.1 Daily work
Including "six checks, six diligence", that is, checking whether the crab activities are normal and diligent in patrol ponds, insisting on patrol pools in the morning, middle and evening; checking whether the crab body is deprived of oxygen and doing the sanitation work to improve water quality. Check whether there are predator creatures in the pond, and remove the enemy's harmful creatures. Check if there are soft shell crabs in the crab ponds, and protect the soft shell crabs. You can cast more palatable animal feed to restore the stamina as soon as possible. The ability to defend against predators; to check if crabs are sick, to prevent and treat crabs; to check and prevent the escape facilities of crab ponds, and to maintain them. In addition, in daily work, be sure to keep the crab pool environment quiet and comfortable, do not interfere too much with the crab feeding, oyster shell process, feed, clean the food field to light, in order to improve the survival rate of shell crab. At the same time, we must do a good job in keeping a record of the culture ponds.
7.2 Routine detection
Regularly test the biological characteristics of the cultured crabs, aquaculture hydration indicators, and make records. Content includes: collection, processing and preservation of water samples. General sampling should be able to represent the comprehensiveness of crab pond waters, preferably in the morning; the number of sampling times can be determined according to needs; sampling depth should be based on water depth conditions, a layer is collected at certain intervals, and cryogenic preservation is adopted. The analysis of fishery water quality should mainly consider physicochemical factors that are most closely related to crab culture. The conventional standard analysis method is the main method for the current water quality analysis.
8 Crab fishing
8.1 Fishing time
When the proportion of mature crabs in the gonads accounts for 80% of crabs, fishing is usually done in October.
8.2 Fishing methods
There are mainly three kinds of fishing methods, such as ground cage fishing, water fishing, and silicon fishing. Among them: the cage fishing method is the most practical fishing method. Water fishing method: In the water inlet, a fishing net type fishing gear is opened, and the water outlet is opened so that the water flows, and the crab crawls into the water with the water. Pay attention to two points: one point is that one discharge of water is inexhaustible, and the pool water should be added to the depth of 0.2---0.3m, then the water should be added, and then the water should be discharged again. This is repeated several times; the other point is that after the pool water is discharged, the river crabs are all out. In the evening, climb up the bank to the edge of the escape wall, which can be captured manually.
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