Study on Artificial Breeding Techniques of Blue Grouper

The blue grouper is a genus, a fish, and a grouper, commonly known as bandits and waxpots. Rich in southern Fujian and Guangdong coasts, it is used for fish consumption. Its live fish are sold well in Hong Kong and Macao. In order to adjust the species structure of marine fish farming in eastern Yunnan and improve the economic benefits of breeding, the artificial reproduction technology of blue grouper was studied in the Fujian East Aquatic Products Institute.
     Materials and Methods
    1. Origin and Cultivation of Broodstock
    (1) Origin of broodstock       On April 12th 2000, 36 3-4 species of blue grouper developed from cages in Lianjiang County, Fujian Province ( The fish species are from Dongshan County, Fujian Province, with an average weight of 1.1  kg.
    (2) Net cage cultivation in the sea    The broodstock cage cultivation in the sea area is carried out in the fishery sea area of ​​Ningde City. The cage size is 3m3m x3m, and the cultivation time is from 2000. From April 12 to April 25, 2002, bait was eaten with bonito or frozen and fresh fish, and the rate of feeding was 1%-5%, twice daily. The sea water temperature range is 12-29°C, and the salinity range is 24-31.
    (3) Maturation of male broodstock     conducted from March 20 to May 20, 2001, selecting 12 individual large brooders in cages in the sea area In medium feeding alone (semen was not squeezed at the time), methyltestosterone 1 mg/kg and multivitamins 2 to 3 g/kg were added to the diet.
    (4) Intensive cultivation of indoor pools    From April 25 to May 22, 2002, broodstock was moved to an indoor cement pool (30m3) for intensive cultivation. Water temperature Control at 25 °C, fed with squid or squid, feed rate of 3% -6%, add VE capsules in the bait 30 grains / d, daily water change of 100%, low light, aerated feeding.
    2. Pro-fish gonads promote ripening and oxytocin production
    On May 8, 2002, gonads were cooked and intramuscularly injected with LHRH-A2 at a dose of 0.5ug/kg. Fertility was induced at 9:00 AM on May 22 and intramuscular injection of HCG-L-LHRH-A2 was given at doses of 1500 IU/kg and 2.5 ug/kg, respectively. The water temperature is controlled at about 25°C.
    3. Indoor nursery main facilities
     20m2 cement pool, 30m2 cement pool, and the pool depth is 1.5m.
    20m2 sand filters, 2.0m pool depth, and 2.2kw aerators.
    4. Fertilized egg collection and hatching
    Fertilizing the fertilized eggs in a spawning pond with a sieve. After being selected, the fertilized eggs will be placed in a nursery and juvenile culture pond (area of ​​20m2, water depth of 1.4m), micro-inflated hatching, hatching density It is 115,000 grains/m3. The hatching water temperature is 25.0°C and the salinity is 33.6 (the salinity in the sea area is 29.6, and salt is increased with salt).
    5. Larval rearing
    (1) Environmental conditions    Light intensity 500-3000 lx, Water temperature range 24.8-28.0°C, Salinity range 29.2- 33.6,PH The value of 8.1 to 8.4, D0 value of 6.4-6.9mg / L, ammonia nitrogen content of 0.10-0.12mg / L. The distribution density of air stones in nursery ponds is 0.6/m2, and micro-inflated.
    (2) Feed series and its feeding    Bait series are: 1 larvae opening to 12 days old - Mushun fertilized eggs or larvae larvae 10~0 /ml; 28-20 days of age - rotifers 5-10 / ml; 215-20 days of age - Artemia nauplii 2 to 3 / ml; 418 days to emergence - copepod 0 .5 to 2/m1. The rotifers and Artemia should be bred with Chlorella or fortifier for 6h and then fed. Copepods should be collected from the sea area.
    (3) Water Quality Control    After hatching of larvae, the mucous membranes of the water surface are promptly removed, and 80 mesh cages are used for microfluidic water exchange, with a water change of approximately 1 /3. For larvae, the amount of water changed from 4 to 10 days was 1/4 to 1/3, from 11 to 20 days to 1/3 to 3/4, from 21 to 30 days to 3/4 to 100%, and from 30 to 40 days. 100% - 200%. At the age of 7 to 15 days, the sewage was sucked once every other day. After 16 days of age, the sewage was sucked 1-2 times a day to keep the pool water clean.
    (4) larval rearing density     larval rearing density ranged from 93,000 to 0.300/m3. As the individual grows, the incubation density is gradually diluted. The 1-day-old cultivation density was 93,000 pigs/m3 (1 mouth of 20m2 pool). At the age of 5 days, it was divided into 2 mouths (2 mouths of 20m2 pool) with a density of 40,000 tails/m3 and 37,000 respectively. Tail/m3; at the 13th day of age, the second sub-pooling was performed, adding a mouth of 30 m2 pool with a density of 13,000/m3, 15,000/m3, 12,000/m3; The density is about 0.3 million/m3.
    (5) Size sorting cultivation    When larvae and juveniles enter 20 days of age, the size gap gradually increases, at this time the dorsal fin, pelvic fin, pectoral fin spine Long and hard, it is not appropriate to sort. At the age of 35 days, the fin spines almost disappeared and their physiques were strong. They can be sorted according to the individual's large, medium, or small size and continue to be cultivated.
    (6) Add chlorella fluid    From larval hatching to larvae and juveniles at 30 days of age, add 30-50 million cells/m1 to the nursery pool each day. In order to improve the water quality of nursery ponds, reduce the transparency of the water body, and make the rotifers that are larval foods not be hungry, and meet the needs of larval fish for unsaturated fatty acids.
     Results   Fruit
    1. Broodstock breeding
    The broodstock was cultivated in cages in the sea area for 2 years, with an average weight of 1.8 kg (1.5-2.2 kg) and a weight gain rate of 38.9%. After 2 months of male development, 11 males were turned and semen was shed during extrusion. The rate of male to female was 91.6%. In the indoor cement pool cultivation, the gonads can be further matured. After maturation and cultivation, the abdomen of the female fish is obviously enlarged, and the color of the male fish is obvious, which meets the requirement of brooding fish production.
    2. Progeny fish spawning and hatching
     After spawning, spawning begins at 34h (19:00 on May 3) and the male fish chases the female. On May 24th, at 7:00 am, eggs were weighed at 2.1kg, of which fertilized eggs were 1.6kg and the fertilization rate was 76.2%. The diameter of the fertilized eggs is 0.81mm, and the number of eggs per kilogram is about 2 million, accounting for 3.2 million eggs. The larvae were hatched (incubation time 26h) on May 24th, 21:00, and about 2.6 million larvae were hatched. The hatching rate was 80.7%. At the temperature of 25°C, the hatching process of fertilized eggs is shown in the attached table.
    3. Larval rearing
    The newly hatched larvae have a total length of 1.2mm, and their yolk sac is large, accounting for 1/2 of their body length; the yolk sac is basically absorbed after the larvae are hatched and begins to feed on the bait; up to 5 The stomach sac (light yellowish green) can be clearly seen at the age of the day, and the food intake increased significantly. At the age of 11 days, the fin spines began to grow and gradually grow. By the age of 25 days, the fin spines and caudal fins are the same length as the aircraft; 28 The fin spines begin to shorten at age, and the fin spines disappear at 35 days of age. The food series chosen in this project is suitable for the feeding and nutritional requirements of juvenile blue groupers. Juvenile fish grow fast and have a high survival rate. The larvae have entered the juvenile period since they were accepted on July 4. Their average length is 3.79cm. The total number of fry in the three ponds is 190,000. The survival rate is about 7.3%.
     Summary and Discussion
    1. Intensive cultivation of broodstock
    The broodstock used for artificial breeding must be intensively cultivated. During the breeding process, nutrient-rich high-quality bait and appropriate environmental conditions should be provided so as to meet the nutritional accumulation required for broodstock ovary development. Doing a good job of cultivating male broodstock to promote male sexual maturity is the key to artificial reproduction.
    2. Raising salinity is conducive to the hatching of fertilized eggs
    Two different salinity contrast tests were performed in fertilized egg hatching. The salinity was 33.6‰, and the fertilized eggs went up quickly. The hatching rate was 80.7%. The salinity was 29.5‰ (a small amount of tests). The fertilized eggs were half ups and downs, and the hatching rate was only 60%. It shows that increasing salinity is beneficial to the hatching of fertilized eggs of blue grouper.
    3. High quality open bait for larvae
    Oysters fertilized eggs or larvae larvae are ideal for bait larvae, their size, vitality, nutrition and other conditions in line with the requirements of blue grouper larvae began feeding. In this experiment, the survival rate of larvae after 7 days of opening is 70%, which can be said to be higher.
    4. Three death peaks of larval fish and their countermeasures
    (1) Three Peak Death Periods and Causes of Early Juveniles The first death peak period is 6 to 9 days. At this time, the larvae are transformed from endogenous nutrients to external nutrition, and the weaker ones and the sub-fish that do not feed on the bait are to be eliminated. The second peak of death is 15-20 days old. At this time, it is the conversion period of the bait species, the rotifers have stopped feeding, Artemia is used as the main bait, and the copepods have just started feeding. Most larvae cannot feed copepods. This stage is mainly due to nutritional reasons and lead to a large number of deaths. The third peak of death is between 25 and 30 days of age. At this stage, the larvae and juveniles have large individual differences, and they are unable to sort. As a result, they cause mutual food and cause massive deaths. However, some large individual juveniles were found to have died in the trial. The reason for this is to be continued in the future.
    (2) Responses  
    1 Pay attention to the nutritional requirements of larvae on bait. Both rotifers and Artemia nauplii cultured with yeast lack unsaturated fatty acids, so nutrient fortification must be performed before feeding to increase the content of unsaturated fatty acids. After 15 days of age, as early as possible to feed small individuals of the copepod, because Artemia nauplii lack unsaturated fatty acids, even if the enhanced culture, the effect is not good (Artemia nauplii does not open to feed, rely on the appearance of some adhesion The nutrients are limited. Therefore, the feeding time of Artemia nauplii should be shortened as early as possible, and small individuals copepods filtered by the 80-mesh sieve should be fed early to avoid dying of juvenile fish due to the lack of unsaturated fatty acids.
    2Provide sufficient high-quality bait and timely sorting and cultivation to reduce deaths from mutual killings.
    5. Fertility method for obtaining fertilized eggs remains to be improved
     Grouper is a spawning fish, its gonads are gradually mature. The use of drug eliciting will cause those immature eggs to be produced together, resulting in a low hatch rate. For those eggs that are not mature enough, even if they are fertilized, hatched larvae will die due to congenital deficiency, resulting in a waste of broodstock resources. Therefore, broodstock breeding should be strengthened to allow natural spawning after the gonads have fully matured.