With the development of the crab breeding industry and the growing scale of seedlings in various regions, the industrialization of crabs has also received increasing attention. How to cultivate good seedlings, raise healthy seedlings, increase the yield and survival rate of crab seedlings, and besides being subject to some objective conditions, technical conditions are the most important ones. Now based on my years of experience and experience in river crab breeding work, On the issue of raising the production and quality of factoryized crab breeding, talk about your own opinions.
First, the selection of pro-crab crabs The individual weight of pro-crabs is 75-125 grams, which is the best. It requires a healthy body, a healthy body, a greenish-green body, belly-white, and no parasites or other attachments on the crab body surface. In addition, the collection of pro-crabs should not only be in one place or in one pond, and it is better to choose in multiple places, especially the male and female pro-crab crabs, which should avoid inbreeding to the greatest degree.
Second, the bait before the nursery training In the entire larval rearing process, the quality of food, species and feeding methods, play a decisive role in the survival rate of larvae. In the early stage of nursery, due to the high density of seedlings, natural algae can not meet the needs of the growth and development of the juvenile larvae. This requires that the density of the monocytic algae in the nursery ponds be raised to 150,000-200,000 before harvesting. / ml or more, after regular supplements. This not only satisfies the needs of vegetative foods in the early stage of the larvae, but also promotes the survival rate after the pupa metamorphosis. It also ensures the virtuous circle in the ecological balance of the nursery pond water and plays a role in purifying water quality.
Third, the density of seedlings The density of seedlings is closely related to the survival rate of larvae. If you want to improve the survival rate of seedlings and increase the yield, you must reasonably grasp the density of seedlings. Under normal circumstances, the density of seedlings is generally 250,000 - 400,000/square meter. If the nursery pond is relatively lean (the amount of plankton in the water is too small), or the number of cultivated single-cell algae is not enough, the density of the collected seedlings will be relatively less, generally 150,000-200,000/square meter is better. If the water in the nursery pond (the amount of plankton in the water is large), the various machinery and equipment provided during the nursery will meet the requirements of the technical regulations, and the technical level will be correct. The density of the seedlings can be relatively increased, and the ship will be 450,000. - 550,000 / square meters, so that the larvae to Z4 or the second day of training.
It is worth noting that the time for picking seedlings in the same pond cannot be dragged too long to prevent inconsistency due to picking time, resulting in uneven development of larvae and causing fratricide.
Fourth, the management of larvae After harvesting, the most important task is to observe the larvae's feeding conditions and activities. If less than 50% satiety, we must appropriately increase the unicellular algae and rotifers (if feeding Small brine shrimp, it is best to use hot water or about freezing. Generally Z2 at the end of the rotifer Z2, Artemia feed amount can be maintained 3-5 / ml, egg yolk feed 8 times a day, each feeding amount of 1 mg / liter, since Z, end, Z; Artemia nauplii was the main feeding amount of 4-6/ml and egg yolk 1.5 mg/l. At the end of the term, the amount of Artemia should be increased, increasing to 4-8/ml and observing at any time. If there is not enough feed, feed it at any time to prevent the larvae from self-mutilation and add 1.5 mg/L of egg tarts. . Large-eyed larvae mainly Artemia adults, but also can feed some fish, shrimp, meat and other rules. Feeding volume 12 times a day, 1 mg/L each time. In the early period of Z1, the feeding amount of rotifers or Artemia should be appropriately controlled. If the amount is too large, it will spread in the later stages, compete with the larvae for space, compete for feed, and consume water and lack of baits in the larvae and death due to lack of oxygen. .
V. Changing water and temperature
Zl larvae to add water, the temperature of 18-19 °C is appropriate. The water exchange volume accounts for 1/5 of the whole pool, and the water changing net is 80-100 meshes, and the water temperature is 20-21 degrees Celsius. Z; change the amount of water per day accounts for 1/3 of the total pool water, change the water mesh 60 mesh, water temperature 22-23 °C. Z4, Z5 change the water twice a day, each time the amount of water changes account for 1/2 of the total pool water, mesh 40 mesh, water temperature 24-25 °C. Large-eyed larvae change water 2-3 times a day, each time changing water accounts for 2/3 of the entire pool of water. During the entire management stage, it is necessary to observe the feeding situation of the larvae and the changes in the water quality, flexibly control the amount of feed and the amount of water to be changed, and find that the situation is solved in time.
Sixth, the light intensity of the light on the survival rate of the juvenile larvae have a great relationship, especially when the larvae to Z4, Z5, the larvae of light, crowded more strongly, so that during the day when the sun is strong, try to Blocked with a blind, allowing light to shine more evenly in the nursery pool, so that the larvae are no longer clustered. On cloudy days or in the evening, if the lighting equipment is better, you can find two good angle lamps on both sides of the nursery pond and try to make the lights evenly shine in every corner of the nursery. This will not only prevent z5 and large eye larvae from gathering due to lack of oxygen or self-mutilation and lead to a large number of deaths, but also ensure normal feeding and metamorphosis of larvae.
VII. The time for pooling crabs to go out of pond should be 3-4 days for bigeye larvae. The temperature of the nursery pond water is basically the same as the outside natural water temperature, and the salinity is 4%-6%. about. From the outside, the vitality of crab seedlings is strong. The seedlings are rested neatly, and they can be quickly evacuated in their hands. After draining the water, they can be quickly and evenly distributed in the seedling box. In this way, large-eyed larvae can be completely out of the pool.
VIII. Water for disease control and nursery If the water containing heavy metal ions is too high, the EDTA sodium salt should be properly treated. When changing the water, it is necessary to supplement the water according to the amount of water exchanged so as to reduce the toxicity of heavy metal ions to juveniles. During the entire nursery period, some drugs such as oxytetracycline, nitrofurazone, norfloxacin, and chloramphenicol should be regularly administered to the pool. The dosage is generally 0.5-2 mg/l. Drugs can be used interchangeably, so the effect is better. While doing a good job of prevention work, during the entire period of nursery, the larvae should be frequently examined by microscopy and the disease should be promptly taken effective measures for treatment.
First, the selection of pro-crab crabs The individual weight of pro-crabs is 75-125 grams, which is the best. It requires a healthy body, a healthy body, a greenish-green body, belly-white, and no parasites or other attachments on the crab body surface. In addition, the collection of pro-crabs should not only be in one place or in one pond, and it is better to choose in multiple places, especially the male and female pro-crab crabs, which should avoid inbreeding to the greatest degree.
Second, the bait before the nursery training In the entire larval rearing process, the quality of food, species and feeding methods, play a decisive role in the survival rate of larvae. In the early stage of nursery, due to the high density of seedlings, natural algae can not meet the needs of the growth and development of the juvenile larvae. This requires that the density of the monocytic algae in the nursery ponds be raised to 150,000-200,000 before harvesting. / ml or more, after regular supplements. This not only satisfies the needs of vegetative foods in the early stage of the larvae, but also promotes the survival rate after the pupa metamorphosis. It also ensures the virtuous circle in the ecological balance of the nursery pond water and plays a role in purifying water quality.
Third, the density of seedlings The density of seedlings is closely related to the survival rate of larvae. If you want to improve the survival rate of seedlings and increase the yield, you must reasonably grasp the density of seedlings. Under normal circumstances, the density of seedlings is generally 250,000 - 400,000/square meter. If the nursery pond is relatively lean (the amount of plankton in the water is too small), or the number of cultivated single-cell algae is not enough, the density of the collected seedlings will be relatively less, generally 150,000-200,000/square meter is better. If the water in the nursery pond (the amount of plankton in the water is large), the various machinery and equipment provided during the nursery will meet the requirements of the technical regulations, and the technical level will be correct. The density of the seedlings can be relatively increased, and the ship will be 450,000. - 550,000 / square meters, so that the larvae to Z4 or the second day of training.
It is worth noting that the time for picking seedlings in the same pond cannot be dragged too long to prevent inconsistency due to picking time, resulting in uneven development of larvae and causing fratricide.
Fourth, the management of larvae After harvesting, the most important task is to observe the larvae's feeding conditions and activities. If less than 50% satiety, we must appropriately increase the unicellular algae and rotifers (if feeding Small brine shrimp, it is best to use hot water or about freezing. Generally Z2 at the end of the rotifer Z2, Artemia feed amount can be maintained 3-5 / ml, egg yolk feed 8 times a day, each feeding amount of 1 mg / liter, since Z, end, Z; Artemia nauplii was the main feeding amount of 4-6/ml and egg yolk 1.5 mg/l. At the end of the term, the amount of Artemia should be increased, increasing to 4-8/ml and observing at any time. If there is not enough feed, feed it at any time to prevent the larvae from self-mutilation and add 1.5 mg/L of egg tarts. . Large-eyed larvae mainly Artemia adults, but also can feed some fish, shrimp, meat and other rules. Feeding volume 12 times a day, 1 mg/L each time. In the early period of Z1, the feeding amount of rotifers or Artemia should be appropriately controlled. If the amount is too large, it will spread in the later stages, compete with the larvae for space, compete for feed, and consume water and lack of baits in the larvae and death due to lack of oxygen. .
V. Changing water and temperature
Zl larvae to add water, the temperature of 18-19 °C is appropriate. The water exchange volume accounts for 1/5 of the whole pool, and the water changing net is 80-100 meshes, and the water temperature is 20-21 degrees Celsius. Z; change the amount of water per day accounts for 1/3 of the total pool water, change the water mesh 60 mesh, water temperature 22-23 °C. Z4, Z5 change the water twice a day, each time the amount of water changes account for 1/2 of the total pool water, mesh 40 mesh, water temperature 24-25 °C. Large-eyed larvae change water 2-3 times a day, each time changing water accounts for 2/3 of the entire pool of water. During the entire management stage, it is necessary to observe the feeding situation of the larvae and the changes in the water quality, flexibly control the amount of feed and the amount of water to be changed, and find that the situation is solved in time.
Sixth, the light intensity of the light on the survival rate of the juvenile larvae have a great relationship, especially when the larvae to Z4, Z5, the larvae of light, crowded more strongly, so that during the day when the sun is strong, try to Blocked with a blind, allowing light to shine more evenly in the nursery pool, so that the larvae are no longer clustered. On cloudy days or in the evening, if the lighting equipment is better, you can find two good angle lamps on both sides of the nursery pond and try to make the lights evenly shine in every corner of the nursery. This will not only prevent z5 and large eye larvae from gathering due to lack of oxygen or self-mutilation and lead to a large number of deaths, but also ensure normal feeding and metamorphosis of larvae.
VII. The time for pooling crabs to go out of pond should be 3-4 days for bigeye larvae. The temperature of the nursery pond water is basically the same as the outside natural water temperature, and the salinity is 4%-6%. about. From the outside, the vitality of crab seedlings is strong. The seedlings are rested neatly, and they can be quickly evacuated in their hands. After draining the water, they can be quickly and evenly distributed in the seedling box. In this way, large-eyed larvae can be completely out of the pool.
VIII. Water for disease control and nursery If the water containing heavy metal ions is too high, the EDTA sodium salt should be properly treated. When changing the water, it is necessary to supplement the water according to the amount of water exchanged so as to reduce the toxicity of heavy metal ions to juveniles. During the entire nursery period, some drugs such as oxytetracycline, nitrofurazone, norfloxacin, and chloramphenicol should be regularly administered to the pool. The dosage is generally 0.5-2 mg/l. Drugs can be used interchangeably, so the effect is better. While doing a good job of prevention work, during the entire period of nursery, the larvae should be frequently examined by microscopy and the disease should be promptly taken effective measures for treatment.