The three-ported crab grows quickly and has a high food value. It is an excellent breed of artificial breeding. In recent years, with the drastic reduction of natural resources, the scale of breeding has been expanding year by year, and at the same time it has also led to an increase in the demand for high-quality crab seedlings. In order to solve the problem of large-scale seedling cultivation and raise the level of seedling raising technology, we conducted a productive artificial seedling test of the crab in the spring of 2002. The average yield of young crabs was 3,000/m3, and the maximum yield was 5000/m3. Good economic benefits. The process and key technologies for this nursery are summarized below. ?
1 Materials and Methods?
1.1 Pro-crab source On March 30th, 50 pro-crabs were purchased from Rizhao City Development Co., Ltd.'s wintering room, and the outer eggs were orange-colored and kept in a cement pool of 50m3. The water temperature was 16°C. Pro-crabs were bathed with 110-6 potassium permanganate before entering the pool to kill pathogenic organisms such as polychaetes.
1.2 The dietary crab diet is variegated pupa and sandworm; the crab cultivation feed is Chaetoceros, gold algae, egg yolk, rotifer, Artemia and so on.
1.3 Attachment The 10 mesh mesh piece is used to put the mesh (210-6 potassium permanganate soaked) into the larval rearing tank immediately after the larvae have changed to big larvae. ?
1.4 Heating facilities One 1t boiler for steam heating is used. The nursery water is preheated by the preheating tank and the heating method is closed coil heating.
1.5 1.5kW blower is installed in the inflatable facility, and 15 aerials are installed in each nursery pond.
2 main technical measures?
2.1 pro-crab stocking?
2.1.1 The preferred crab is selected from the group that has strong vigor, complete appendages, solid egg mass, and clear edged female eggs. During transport, care should be taken to prevent crab body damage and dry outer eggs, so as not to affect the hatching rate. ?
2.1.2 Strengthen the culture of the crab culture The bottom of the culture pond is sanded 10~15cm, the sand deposition area accounts for 60% of the bottom area of ​​the pool, and 40% of the open space near the drain outlet is used for feeding, changing water and removing residual baits. The top of the pool is covered with black film to protect the light. The daily feeding amount is 15%, the water is changed by 1/3 per day, and the residual bait is removed every 2 days. Observe the changes in the color of the outer egg during the intensive treatment of the crabs or observe the development of the embryo under the microscope. If the color of the outer egg is dark gray and purple, the heart beat of the ovary within the egg membrane reaches 100 beats/min. Incubation, the larval pool needs to be prepared at this time. ?
2.1.3 Ways of warming During the strengthening period of pro-crab raising, the temperature is gradually raised from the entering room temperature of 16°C, and the temperature is gradually increased by 0.5°C until 20°C. ?
2.1.4 Strict prevention through strict disinfection of the pro-crab pool, clear pond, forbid the feeding of metamorphic bait, remove dead crabs and other measures to eliminate the root cause, cut off the route of transmission; at the same time, regular sprinkling fluoride 1mg/L or formaldehyde 2010-6 To inhibit the growth of bacteria and parasites.
2.2 larval rearing?
2.2.1 Collection of larvae The mature crabs of the eggs are washed with 4010-6 nystatin for 20 minutes and then transferred into the nursery ponds for discharge. The density of larvae is controlled within 100,000/m3, the density is too large, cultivation is difficult, the final survival rate is low, and even the cultivation fails. ?
2.2.2 Control of water temperature The temperature of larvae during the incubation period is preferably 21 to 26°C, and the temperature is gradually increased. Among them, Z1: 20 to 21° C.; Z2: 21 to 22° C.; Z3: 22 to 23° C.; Z4: 23 to 24° C.; M: 24 to 26° C., gradually dropping to natural water temperature after hatching.
2.2.3 Inflatable air stone density is more than 1 / m? 2, Z1 ~ Z2 aeration is microwave-like; Z3 ~ Z4 aerated, to the big eye larvae and crab period is boiling-like. When changing the water, adjust the gas volume in time with the change of the water level to prevent the bottom membrane from breaking, resulting in a “pan bathâ€. ?
2.2.4 Water quality control During the period of Z?1, water is added in 20cm on a daily basis; Z2 starts to change water, and the amount of water exchanged per day is: Z2 20%, Z3 50%, Z4 60%, and big eye larvae and juvenile crab period 80% to 150%, changing water The temperature difference should be less than 1°C. The routine water quality tests were conducted every other day. The main water quality indicators were pH 7.8 to 8.6, DO 4.5 to 5.5 mg/L, salinity 28 to 30, and light 500 to 2000 lx. 2.2.5 Feeding of baits Feeding nursery stocks in advance, single-celled algae are used as larval open baits with a density of 50,000 to 100,000/ml. At the early stage of larval rearing, monosomic algae and rotifers are predominant, and Artemia nauplii is mainly used in the middle period, combined with feeding algae powder and shrimp slices. In the later period, the Artemia adults were the dominant species. The feeding amount was approximately 100% to 150% of the juvenile body weight, and the feeding interval was 3h. This feeding method can greatly reduce the amount of Artemia in vivo and reduce the production cost. ?
2.2.6 Attachment base After the larvae have all metamorphosed as big eye larvae, put a polyethylene net sheet into the cultivation pond, and cast 1 square meter mesh per cubic meter of water body. Don't let the mesh be exposed when you put it in order to prevent larvae from dying. ?
2.2.7 Disease Prevention Disease prevention and control during larvae cultivation should be based on prevention. Before the production, the sedimentation tanks, larval rearing tanks and tools should be strictly sterilized; the cultivation water should be treated with 510-6 EDTA; regular use of antibiotics (1～2)10-6. Antibacterial; hanging cage before the crabs with 4010-6 nystatin disinfection for 20min; feeding live rotifers and halogen larvae, strengthen larval nutrition, improve resistance to disease. ?
3 Results and Discussions?
3.1 results?
3.1.1 Crab-cultivation Fifty spawning crabs were bred in the room for 20 days and survived. The survival rate was 74%. Five eggs were basically shed and 32 hatched. ?
3.1.2 Seedling results From the beginning of the April 15 pond to the end of April 25, 32 of the 3 crabs of the Phase II juvenile crabs were bred together with an average of 3000/m3, and the survival rate of the larvae reached 13.8%. The number of larvae. ?
3.2 Discussion?
3.2.1 Gradually raise the temperature steadily The warming of crabs should not be overheated too quickly, so as to avoid unsynchronized egg development. ?
3.2.2 Bait larvae cultivation In addition to having good water quality conditions, palatable baits are also the key to success. We put early single-celled algae in the nursery pond. Once the larvae are discharged, there will be sufficient food, and the metamorphosis rate and survival rate will be high. ?
3.2.3 Management timely put mesh attachment bases to reduce mutual killing and improve survival rate. Large-eyed larvae and juvenile crabs kill each other severely, especially for the development of unsynchronized larvae when they are bred together, they will eat small, strong eat weak. ?
3.2.4 Disease Prevention The key to maintaining normal seedlings and raising the survival rate is disease prevention and control. We bathed the young pro crab before bathing with 4010-6 nystatin for 20 minutes, basically inhibiting the proliferation of bacteria and parasites.
1 Materials and Methods?
1.1 Pro-crab source On March 30th, 50 pro-crabs were purchased from Rizhao City Development Co., Ltd.'s wintering room, and the outer eggs were orange-colored and kept in a cement pool of 50m3. The water temperature was 16°C. Pro-crabs were bathed with 110-6 potassium permanganate before entering the pool to kill pathogenic organisms such as polychaetes.
1.2 The dietary crab diet is variegated pupa and sandworm; the crab cultivation feed is Chaetoceros, gold algae, egg yolk, rotifer, Artemia and so on.
1.3 Attachment The 10 mesh mesh piece is used to put the mesh (210-6 potassium permanganate soaked) into the larval rearing tank immediately after the larvae have changed to big larvae. ?
1.4 Heating facilities One 1t boiler for steam heating is used. The nursery water is preheated by the preheating tank and the heating method is closed coil heating.
1.5 1.5kW blower is installed in the inflatable facility, and 15 aerials are installed in each nursery pond.
2 main technical measures?
2.1 pro-crab stocking?
2.1.1 The preferred crab is selected from the group that has strong vigor, complete appendages, solid egg mass, and clear edged female eggs. During transport, care should be taken to prevent crab body damage and dry outer eggs, so as not to affect the hatching rate. ?
2.1.2 Strengthen the culture of the crab culture The bottom of the culture pond is sanded 10~15cm, the sand deposition area accounts for 60% of the bottom area of ​​the pool, and 40% of the open space near the drain outlet is used for feeding, changing water and removing residual baits. The top of the pool is covered with black film to protect the light. The daily feeding amount is 15%, the water is changed by 1/3 per day, and the residual bait is removed every 2 days. Observe the changes in the color of the outer egg during the intensive treatment of the crabs or observe the development of the embryo under the microscope. If the color of the outer egg is dark gray and purple, the heart beat of the ovary within the egg membrane reaches 100 beats/min. Incubation, the larval pool needs to be prepared at this time. ?
2.1.3 Ways of warming During the strengthening period of pro-crab raising, the temperature is gradually raised from the entering room temperature of 16°C, and the temperature is gradually increased by 0.5°C until 20°C. ?
2.1.4 Strict prevention through strict disinfection of the pro-crab pool, clear pond, forbid the feeding of metamorphic bait, remove dead crabs and other measures to eliminate the root cause, cut off the route of transmission; at the same time, regular sprinkling fluoride 1mg/L or formaldehyde 2010-6 To inhibit the growth of bacteria and parasites.
2.2 larval rearing?
2.2.1 Collection of larvae The mature crabs of the eggs are washed with 4010-6 nystatin for 20 minutes and then transferred into the nursery ponds for discharge. The density of larvae is controlled within 100,000/m3, the density is too large, cultivation is difficult, the final survival rate is low, and even the cultivation fails. ?
2.2.2 Control of water temperature The temperature of larvae during the incubation period is preferably 21 to 26°C, and the temperature is gradually increased. Among them, Z1: 20 to 21° C.; Z2: 21 to 22° C.; Z3: 22 to 23° C.; Z4: 23 to 24° C.; M: 24 to 26° C., gradually dropping to natural water temperature after hatching.
2.2.3 Inflatable air stone density is more than 1 / m? 2, Z1 ~ Z2 aeration is microwave-like; Z3 ~ Z4 aerated, to the big eye larvae and crab period is boiling-like. When changing the water, adjust the gas volume in time with the change of the water level to prevent the bottom membrane from breaking, resulting in a “pan bathâ€. ?
2.2.4 Water quality control During the period of Z?1, water is added in 20cm on a daily basis; Z2 starts to change water, and the amount of water exchanged per day is: Z2 20%, Z3 50%, Z4 60%, and big eye larvae and juvenile crab period 80% to 150%, changing water The temperature difference should be less than 1°C. The routine water quality tests were conducted every other day. The main water quality indicators were pH 7.8 to 8.6, DO 4.5 to 5.5 mg/L, salinity 28 to 30, and light 500 to 2000 lx. 2.2.5 Feeding of baits Feeding nursery stocks in advance, single-celled algae are used as larval open baits with a density of 50,000 to 100,000/ml. At the early stage of larval rearing, monosomic algae and rotifers are predominant, and Artemia nauplii is mainly used in the middle period, combined with feeding algae powder and shrimp slices. In the later period, the Artemia adults were the dominant species. The feeding amount was approximately 100% to 150% of the juvenile body weight, and the feeding interval was 3h. This feeding method can greatly reduce the amount of Artemia in vivo and reduce the production cost. ?
2.2.6 Attachment base After the larvae have all metamorphosed as big eye larvae, put a polyethylene net sheet into the cultivation pond, and cast 1 square meter mesh per cubic meter of water body. Don't let the mesh be exposed when you put it in order to prevent larvae from dying. ?
2.2.7 Disease Prevention Disease prevention and control during larvae cultivation should be based on prevention. Before the production, the sedimentation tanks, larval rearing tanks and tools should be strictly sterilized; the cultivation water should be treated with 510-6 EDTA; regular use of antibiotics (1～2)10-6. Antibacterial; hanging cage before the crabs with 4010-6 nystatin disinfection for 20min; feeding live rotifers and halogen larvae, strengthen larval nutrition, improve resistance to disease. ?
3 Results and Discussions?
3.1 results?
3.1.1 Crab-cultivation Fifty spawning crabs were bred in the room for 20 days and survived. The survival rate was 74%. Five eggs were basically shed and 32 hatched. ?
3.1.2 Seedling results From the beginning of the April 15 pond to the end of April 25, 32 of the 3 crabs of the Phase II juvenile crabs were bred together with an average of 3000/m3, and the survival rate of the larvae reached 13.8%. The number of larvae. ?
3.2 Discussion?
3.2.1 Gradually raise the temperature steadily The warming of crabs should not be overheated too quickly, so as to avoid unsynchronized egg development. ?
3.2.2 Bait larvae cultivation In addition to having good water quality conditions, palatable baits are also the key to success. We put early single-celled algae in the nursery pond. Once the larvae are discharged, there will be sufficient food, and the metamorphosis rate and survival rate will be high. ?
3.2.3 Management timely put mesh attachment bases to reduce mutual killing and improve survival rate. Large-eyed larvae and juvenile crabs kill each other severely, especially for the development of unsynchronized larvae when they are bred together, they will eat small, strong eat weak. ?
3.2.4 Disease Prevention The key to maintaining normal seedlings and raising the survival rate is disease prevention and control. We bathed the young pro crab before bathing with 4010-6 nystatin for 20 minutes, basically inhibiting the proliferation of bacteria and parasites.
Face Masks are intended to be worn it protect against the spread of
transmission of infections germs patient against infectious germs. This is a single use,
disposable device(s), provided non-sterile.
The product is composed of mask body, nose clip and mask belt, which is a plane ear
hanging structure. The mask body is of three-layer structure, the inner and outer layers
are PP spunbond non-woven fabric, and the middle filter layer is PP melt blown fabric. The
nose clip is made of plasticity material. The material of the mask belt is nylon.
Medical Mask,N95 Medical Mask,Black Medical Mask,Kn95 Medical Mask
Zhejiang Lanhine Medical Products Ltd. , https://www.lanheyiliao.com