The ripening cultivation of broodstock of Penaeus vannamei refers to the process of harvesting the broodstock artificially under the optimal environmental conditions to remove the ocular handle and strengthen the nutrition to promote gonadal development and achieve high quality eggs. The level of broodstock cultivation technology directly affects the quality of broodstock spawning and the effectiveness of shrimp rearing.
First, materials and methods
1. Production sites and facilities. The production site is a broodstock workshop for the prawn thoroughbred farm. The broodstock cultivating pool adopts a semi-buried interior design with an area of ​​40 square meters per pond and a depth of 1.0m. The spawning hatch pool has an area of ​​25 square meters per tank and a depth of 1.4m. The workshop is equipped with power supply, gas supply, heating, water supply and other systems, and can adjust the light intensity.
2. Source of broodstock. The broodstock is a sub-generation F1 of the provincial (Zhanjiang) shrimp bred farm that has been bred through the introduction of elite bred SPF broodstock, and has undergone rigorous testing of F1, followed by breeding, and breeding of F1 broodstock with a shrimp age of 10 months. Individual body weight of females is 35g or more, and male body weight is more than 30g.
3. Broodstock ripening method. The use of cauterized tweezers to excise the unilateral eyelid of the female prawn and to promote the development of gonads by intensive nutrition and water quality assurance measures. Males do not have to remove the eyelids.
4. Induction of mating and egg hatching. During broodstock ripening and cultivation, the gonad development of broodstock is checked at noon every day. When gonads mature to the broodstock of stage IV, the male prawn cultivation pool is harvested by hand dip net, and the broodstock is induced by artificially adjusting the light and water environment. mating. In the evening, mating broodstock (the individuals with spermatozoa adhering to the abdomen of the female) are sent to the spawning pool for spawning. The next morning the spawning broodstock is raised to the female cultivating pool for cultivation. The fertilized eggs are in the weak state. Incubation, larvae can be hatched after 6 hours - 10 hours.
5. The broodstock ripening cultivation management technology
(1) The breeding density of broodstock is 10/m2 - 15/m2.
(2) Water quality factors and water quality control of broodstock cultivation. The temperature of ripening cultivation is 28°C--29°C, and it is incubated at a constant temperature. The temperature difference should be less than 1°C, the pH of the water body should be controlled at 7.8--8.3, and the seawater salinity must be maintained at 23 ‰--30 ‰. When the salinity is low, add salt or sea crystal to adjust.
(3) Adjustment of light. During intense ripening, strong direct light should be avoided, and low light should be preferred. The light intensity of females is controlled at 50Lx-100Lx, and the light intensity of males is controlled at 50Lx--200Lx. In particular, during induction mating (14:00-24:00), two 30-W lamps must be installed above the male pool to increase the light intensity and facilitate mating.
(4) Feeding of bait. Live sandworm, oyster meat, fresh squid, etc. are commonly used bait for broodstock cultivation. The amount of daily feeding is about 25% of the broiler's body weight, which is divided into 6 feedings at regular intervals. The feeding amount should be based on each feeding situation of the broodstock. The number of bait is adjusted flexibly.
6. Disease prevention and treatment during broodstock ripening
(1) Disinfection method. The broodstock cultivation tanks, spawning pools, and tools must be sterilized with 50ppm--100ppm bleach or 30ppm--50ppm potassium permanganate before use. The tools should also be dedicated to the pool. The broodstock should be sterilized with 30ppm Povidone Iodine or 200ppm Formalin for 3 minutes before entering the pond or before spawning.
(2) The secondary sand filter is used for water, and then it can be used after being disinfected by ultraviolet rays. When using it, use 2ppm EDTA complex and heavy metal ions.
(3) Weekly use of drugs to soak shrimp body to prevent fungal infection.
(4) It was found that the diseased shrimp was immediately isolated and symptomatic measures were taken.
Second, broodstock ripening results
1. Gonadal development. The production practice shows that the reproduction mode of Penaeus vannamei is adult -> mature -> mating -> spawning -> larvae. Due to the differences between individual broodstocks, the developmental time of the ovary is not synchronized. The parent's first maturation time for body weight above 35g is approximately 4 days to 30 days. The broodstock has multiple mature spawning characteristics. Two mature spawning intervals ranged from 4 days to 7 days, but after continuous spawning 2 times - 3 times, it took a longer time for the growth of the pod to mature again.
2. The broodstock mating rate and the amount of eggs laid. During the incubation period, the broodstock mating rate (referred to the percentage of mature females selected for mating in the male pool each day) gradually increased with the increase of cultivation time and reached a stable peak after one month. The mating rate was 30% - 40% at the beginning and 60% - 70% after 1 month, and remained relatively stable.
The amount of spawning by broodstock is directly proportional to the size of the broodstock, and the amount of spawning increases with the number of spawnings. By observing broodstock with an average body weight of 35g-40g, it was shown that the first month of spawning was 100,000 to 120,000 tablets and the second month was 140,000 tablets--16 million. Granules, the third month for 180,000 - 200,000 tablets.
3. Production results. From February to May, 1200 groups of self-incubated broodstock were matured and cultivated. A total of 600 million nauplii were cultivated and 200 million tails were cultivated. The fertilized eggs and larvae were abnormally developed and the nursery effect was significant. After 3 months of cultivation, the cumulative mortality rate of broodstock was about 20%, the cumulative number of spawning broodstock was 4,800, and the average number of spawnings per tail was 4 times.
Third, questions and discussions
1. Nutritional issues during the ripening of prawn during broodstocking in South America Penaeus praecox The combination of various high quality live bait feeds is a successful experience in broodstock cultivation. Live shellworm is rich in unsaturated fatty acids, which is the best food, but the price is higher. In production practice, taking every 1000 pairs of broodstock on the daily intake of Nereis is not less than 12.5kg as a reference value. In combination with feeding oyster meat and eel, both good quality and cost savings can be achieved.
Practice has shown that broodstock bait single or bait is not fresh, and even to save costs without feeding sandworm, broodstock physique will decline, the mating rate is low; spawning quality is poor, larval development deformity and even death; maturation slows down Spawning and brooding often spawn in the lower layers of the body of water, spawning secretions and immature follicular cells increased to form more yellow lumps, egg production decreased significantly.
2. Raising the mating rate of broodstock is a key factor affecting the mating rate of ripening and cultivating techniques: (1) Maturity of broodstock, and only mature females accept mating behavior. The male spermatozoon is full of white and marks the maturity of the male. It is also the key to selecting the broodstock and ensuring the mating rate. (2) The appropriate sex ratio also affects the mating rate. Since males are relatively slow to mature, they generally need 15 days to 20 days for maturation. Therefore, it is better to have males and females equal to or greater than 1. (3) Influence of environmental conditions. During induction mating (14:00 - 24:00), the pool of shrimp must be refreshed, the lighting is controlled at about 200Lx, and artificial light must be added at night; the amount of aeration is microwave and the aeration tube is vertically placed in the center of the pool. It will hinder the swimming of broodstock and increase the mating rate.
3. Reducing broodstock mortality is a major technical problem to be solved during broodstock maturation of Penaeus vannamei. In production practice, there are two main deaths during broodstock cultivation. The first time was the initial stage of the transfer of the broodstock from the outdoor to the indoor pool. The main reason was the environmental mutation and the death caused by the mechanical damage; the second occurred within three days after the excision of the female eyelid, mainly wound infection and injury. In addition, broodstock nutrition and unscientific, improper prevention of disease measures, poor water quality control is often a factor of increased mortality.
The biggest change in the water quality that affects the quality of production is that the feeding is overdone and not treated in time, causing the residual baits to stink and spoil, thereby increasing the amount of nitrite in the water and causing disease, resulting in a large number of broodstock deaths. Measures to reduce mortality of broodstock include: (1) The cool weather should be selected when the broodstock is moved into the room, and the indoor water temperature should be adjusted to a lower range to avoid the high temperature period. (2) Temporary water for broodstock disinfection uses ultraviolet sterilizers to disinfect seawater, and put 10ppm of useful live bacteria to inhibit germs to form dominant populations. The water quality of the broodstock pool should be monitored with nitrite nitrogen so that the nitrite nitrogen content is less than 0.1 mg/L. Production shows that once the nitrite nitrogen content is greater than 0.3 mg/L, some mature broodstock will die. (3) When the resection of the eye socket is performed, the temperature of the mattress is higher and the movement is faster, so that the incision heals quickly and the body surface of the shrimp is disinfected with the medicine for 1 minute. (4) During the incubation, individual body surface symptoms, such as red body, corpus luteum, and bloated broodstock, were found to be immediately isolated and the drug pool was used. (5) Regularly add deep-sea fish oil, vitamin C, and immuno-polysaccharides to the feed to increase the broodstock immunity.
4. The mating and spawning broodstock selection time should be reasonably arranged due to the fact that the time of mating and spawning of Penaeus vannamei is not synchronized, usually mating several hours before spawning. The mating time is from 4 pm to 12 pm, and the maturity is relatively high. Good broodstock, whether mated or not, can lay eggs, and spawning time is usually from 21 o'clock to 4 o'clock the next morning. Therefore, the time for selecting mating broodstock to move into the spawning pool should be divided into two times, the first time The evening at 8 pm and the second time at 12 pm will help improve the mating rate of mature broodstock, avoid early mating of broodstock and lay eggs early in the male pool, and also avoid partial mating due to premature selection. The late selection of broodstock causes a waste of resources and affects the cultivation effect.
First, materials and methods
1. Production sites and facilities. The production site is a broodstock workshop for the prawn thoroughbred farm. The broodstock cultivating pool adopts a semi-buried interior design with an area of ​​40 square meters per pond and a depth of 1.0m. The spawning hatch pool has an area of ​​25 square meters per tank and a depth of 1.4m. The workshop is equipped with power supply, gas supply, heating, water supply and other systems, and can adjust the light intensity.
2. Source of broodstock. The broodstock is a sub-generation F1 of the provincial (Zhanjiang) shrimp bred farm that has been bred through the introduction of elite bred SPF broodstock, and has undergone rigorous testing of F1, followed by breeding, and breeding of F1 broodstock with a shrimp age of 10 months. Individual body weight of females is 35g or more, and male body weight is more than 30g.
3. Broodstock ripening method. The use of cauterized tweezers to excise the unilateral eyelid of the female prawn and to promote the development of gonads by intensive nutrition and water quality assurance measures. Males do not have to remove the eyelids.
4. Induction of mating and egg hatching. During broodstock ripening and cultivation, the gonad development of broodstock is checked at noon every day. When gonads mature to the broodstock of stage IV, the male prawn cultivation pool is harvested by hand dip net, and the broodstock is induced by artificially adjusting the light and water environment. mating. In the evening, mating broodstock (the individuals with spermatozoa adhering to the abdomen of the female) are sent to the spawning pool for spawning. The next morning the spawning broodstock is raised to the female cultivating pool for cultivation. The fertilized eggs are in the weak state. Incubation, larvae can be hatched after 6 hours - 10 hours.
5. The broodstock ripening cultivation management technology
(1) The breeding density of broodstock is 10/m2 - 15/m2.
(2) Water quality factors and water quality control of broodstock cultivation. The temperature of ripening cultivation is 28°C--29°C, and it is incubated at a constant temperature. The temperature difference should be less than 1°C, the pH of the water body should be controlled at 7.8--8.3, and the seawater salinity must be maintained at 23 ‰--30 ‰. When the salinity is low, add salt or sea crystal to adjust.
(3) Adjustment of light. During intense ripening, strong direct light should be avoided, and low light should be preferred. The light intensity of females is controlled at 50Lx-100Lx, and the light intensity of males is controlled at 50Lx--200Lx. In particular, during induction mating (14:00-24:00), two 30-W lamps must be installed above the male pool to increase the light intensity and facilitate mating.
(4) Feeding of bait. Live sandworm, oyster meat, fresh squid, etc. are commonly used bait for broodstock cultivation. The amount of daily feeding is about 25% of the broiler's body weight, which is divided into 6 feedings at regular intervals. The feeding amount should be based on each feeding situation of the broodstock. The number of bait is adjusted flexibly.
6. Disease prevention and treatment during broodstock ripening
(1) Disinfection method. The broodstock cultivation tanks, spawning pools, and tools must be sterilized with 50ppm--100ppm bleach or 30ppm--50ppm potassium permanganate before use. The tools should also be dedicated to the pool. The broodstock should be sterilized with 30ppm Povidone Iodine or 200ppm Formalin for 3 minutes before entering the pond or before spawning.
(2) The secondary sand filter is used for water, and then it can be used after being disinfected by ultraviolet rays. When using it, use 2ppm EDTA complex and heavy metal ions.
(3) Weekly use of drugs to soak shrimp body to prevent fungal infection.
(4) It was found that the diseased shrimp was immediately isolated and symptomatic measures were taken.
Second, broodstock ripening results
1. Gonadal development. The production practice shows that the reproduction mode of Penaeus vannamei is adult -> mature -> mating -> spawning -> larvae. Due to the differences between individual broodstocks, the developmental time of the ovary is not synchronized. The parent's first maturation time for body weight above 35g is approximately 4 days to 30 days. The broodstock has multiple mature spawning characteristics. Two mature spawning intervals ranged from 4 days to 7 days, but after continuous spawning 2 times - 3 times, it took a longer time for the growth of the pod to mature again.
2. The broodstock mating rate and the amount of eggs laid. During the incubation period, the broodstock mating rate (referred to the percentage of mature females selected for mating in the male pool each day) gradually increased with the increase of cultivation time and reached a stable peak after one month. The mating rate was 30% - 40% at the beginning and 60% - 70% after 1 month, and remained relatively stable.
The amount of spawning by broodstock is directly proportional to the size of the broodstock, and the amount of spawning increases with the number of spawnings. By observing broodstock with an average body weight of 35g-40g, it was shown that the first month of spawning was 100,000 to 120,000 tablets and the second month was 140,000 tablets--16 million. Granules, the third month for 180,000 - 200,000 tablets.
3. Production results. From February to May, 1200 groups of self-incubated broodstock were matured and cultivated. A total of 600 million nauplii were cultivated and 200 million tails were cultivated. The fertilized eggs and larvae were abnormally developed and the nursery effect was significant. After 3 months of cultivation, the cumulative mortality rate of broodstock was about 20%, the cumulative number of spawning broodstock was 4,800, and the average number of spawnings per tail was 4 times.
Third, questions and discussions
1. Nutritional issues during the ripening of prawn during broodstocking in South America Penaeus praecox The combination of various high quality live bait feeds is a successful experience in broodstock cultivation. Live shellworm is rich in unsaturated fatty acids, which is the best food, but the price is higher. In production practice, taking every 1000 pairs of broodstock on the daily intake of Nereis is not less than 12.5kg as a reference value. In combination with feeding oyster meat and eel, both good quality and cost savings can be achieved.
Practice has shown that broodstock bait single or bait is not fresh, and even to save costs without feeding sandworm, broodstock physique will decline, the mating rate is low; spawning quality is poor, larval development deformity and even death; maturation slows down Spawning and brooding often spawn in the lower layers of the body of water, spawning secretions and immature follicular cells increased to form more yellow lumps, egg production decreased significantly.
2. Raising the mating rate of broodstock is a key factor affecting the mating rate of ripening and cultivating techniques: (1) Maturity of broodstock, and only mature females accept mating behavior. The male spermatozoon is full of white and marks the maturity of the male. It is also the key to selecting the broodstock and ensuring the mating rate. (2) The appropriate sex ratio also affects the mating rate. Since males are relatively slow to mature, they generally need 15 days to 20 days for maturation. Therefore, it is better to have males and females equal to or greater than 1. (3) Influence of environmental conditions. During induction mating (14:00 - 24:00), the pool of shrimp must be refreshed, the lighting is controlled at about 200Lx, and artificial light must be added at night; the amount of aeration is microwave and the aeration tube is vertically placed in the center of the pool. It will hinder the swimming of broodstock and increase the mating rate.
3. Reducing broodstock mortality is a major technical problem to be solved during broodstock maturation of Penaeus vannamei. In production practice, there are two main deaths during broodstock cultivation. The first time was the initial stage of the transfer of the broodstock from the outdoor to the indoor pool. The main reason was the environmental mutation and the death caused by the mechanical damage; the second occurred within three days after the excision of the female eyelid, mainly wound infection and injury. In addition, broodstock nutrition and unscientific, improper prevention of disease measures, poor water quality control is often a factor of increased mortality.
The biggest change in the water quality that affects the quality of production is that the feeding is overdone and not treated in time, causing the residual baits to stink and spoil, thereby increasing the amount of nitrite in the water and causing disease, resulting in a large number of broodstock deaths. Measures to reduce mortality of broodstock include: (1) The cool weather should be selected when the broodstock is moved into the room, and the indoor water temperature should be adjusted to a lower range to avoid the high temperature period. (2) Temporary water for broodstock disinfection uses ultraviolet sterilizers to disinfect seawater, and put 10ppm of useful live bacteria to inhibit germs to form dominant populations. The water quality of the broodstock pool should be monitored with nitrite nitrogen so that the nitrite nitrogen content is less than 0.1 mg/L. Production shows that once the nitrite nitrogen content is greater than 0.3 mg/L, some mature broodstock will die. (3) When the resection of the eye socket is performed, the temperature of the mattress is higher and the movement is faster, so that the incision heals quickly and the body surface of the shrimp is disinfected with the medicine for 1 minute. (4) During the incubation, individual body surface symptoms, such as red body, corpus luteum, and bloated broodstock, were found to be immediately isolated and the drug pool was used. (5) Regularly add deep-sea fish oil, vitamin C, and immuno-polysaccharides to the feed to increase the broodstock immunity.
4. The mating and spawning broodstock selection time should be reasonably arranged due to the fact that the time of mating and spawning of Penaeus vannamei is not synchronized, usually mating several hours before spawning. The mating time is from 4 pm to 12 pm, and the maturity is relatively high. Good broodstock, whether mated or not, can lay eggs, and spawning time is usually from 21 o'clock to 4 o'clock the next morning. Therefore, the time for selecting mating broodstock to move into the spawning pool should be divided into two times, the first time The evening at 8 pm and the second time at 12 pm will help improve the mating rate of mature broodstock, avoid early mating of broodstock and lay eggs early in the male pool, and also avoid partial mating due to premature selection. The late selection of broodstock causes a waste of resources and affects the cultivation effect.