Artificial Seedling Technology of Red Snapper Dune Earthen Pond
The red snapper, commonly known as red snapper, red snapper, and red snapper, belongs to the genus Ovaliformes, Snapperidae, and Snapper, and is a tropical and subtropical medium-lower fish. It usually inhabits water depths of 30cm to 100cm, and its bottom is mud. Silt, belite reefs and other sea areas are mainly distributed in the South China Sea and the East China Sea. In recent years, the red snapper has become one of the important famous varieties of marine aquaculture in southern China, and the artificial breeding technology of the larvae of the red snapper has become more and more mature.
1. Nursery facilities The incubation barrels are cylindrical polyethylene drums with a diameter of 100cm and a height of 90cm. The bottom of the barrel is conical, with a drainage weir, and one aerated stone is set in each incubation barrel. The hatchery is placed under a well-ventilated awning. There are 3 nursery ponds, which are outdoor earthen ponds, with an area of ​​3.5 to 5.0 acres, rectangular or square, 2.0 cm deep, and a depth of about 1.7m. The sediments are muddy and sandy, with a small amount of coral gravel. There are 2 aerators with a power of 520W in each nursery pond. There is a 1.5-acre bait biological pond.
2. Fertilized egg source The fertilized egg is obtained by natural spawning of the broodstock cultured in the cage. After being harvested, washed, weighed, and packaged, the fertilized egg is transported to the nursery.
Second, nursery method
1. Incubation of fertilized eggs The fertilized eggs are placed in a hatching tank filled with filtered seawater. About 1.0 kg of fertilized eggs are placed in each barrel, and the density of fertilized eggs is 1500 particles/L to 2,000 particles/L. . Change the water once every 3 hours to 4 hours. When changing the water, drain the water first and then fill it with fresh seawater. Water quality physical and chemical factors: salinity 30‰, dissolved oxygen content 4mg/L, pH value 7.52, water temperature 28.0 °C. The hatched larvae were fed into the nursery ponds after they were opened for feeding.
2. About 20 days before the nursery ponds are cleared, the first dry ponds are exposed for 5 days to 10 days. Excessive silt is removed, then water is injected 10cm to 20cm. The whole pond is sterilized, and wild fish, crabs, and other predators are removed. . Disinfection and then drying the pond for 3 days to 5 days, and then use 80 mesh sieve bag filter, nursery pond water 30cm wash pond 1 time, and finally into the water depth of about 1.3m. 3 to 5 days after entering the water, observe the water color, if the water color is light green or green, no fertilizer is needed; if the water color is clearer, compound fertilizer can be used for fertilizer and water.
3. After the feed and its feeding larvae are feeding, they can be directly put into the nursery pond for cultivation. The larvae feed on the 15th day of feeding, mainly using rotifers as bait, feeding 8 to 10 times per day; on the 10th to 20th days of age, rotifers, horny horns, and frozen copepods are used as baits. In the main class, the amount of frozen copepods is gradually increased as the larvae age increases, while the amount of rotifers is reduced as the larvae age increases, feeding 8 times a day, feeding The amount of microscopic food is measured as degree; after 20 days of age, fish meat meal and compound feed are started. The ratio of fish meal and eel feed is 10:1, and the daily feed is 3 to 4 times. Just eat enough for the degree, to avoid the appearance of residual bait.
4. Water quality control The first 10 days before the nursery is the static water culture, do not change the water; 10 days later began to change the water, and according to the growth of fry from 20% to 70% gradually increase the amount of water. When water enters the water, 80 mesh sieves are used to filter the seawater to prevent the entry of harmful organisms into the nursery ponds. In the drainage, 150 mesh sieves are used to filter the seawater to prevent the fish from escaping. Oxygenation is usually done in the evening, at night and in the morning. In addition, attention should also be paid to controlling the transparency of the water through fertilization and other methods. The physical and chemical factors of the water body of the nursery: water transparency 50cm-75cm, water temperature 28°C-34°C, pH value 7.90-8.10, dissolved oxygen 4mg/L, salinity 27‰-30‰.
5. Cultivation Density The stocking density is adjusted at any time with the growth of the fry, and the culture density at the early stage of nursery is 20,000/m3 to 30,000/m3, and the cultivation density at the middle stage of breeding is 1000/m2 to 2000/2000. Cubic meters, the rearing period of the cultivation density of 800 / m3 _1000 / m3.
6. Day-to-day management 2 or 3 times a day, and when observing the pond, observe the changes in the amount of water, the amount of basic food organisms in the water, the feeding activity of the fry, the residual bait, and the growth of the fry. Determine the water temperature, salinity, pH, Dissolved oxygen, light and other physical and chemical factors, and from the 15th day of seedling raising, polluted the nursery pond every 2 days.
7. Disease prevention and control adhere to the principle of "prevention first, comprehensive prevention and control". Change the water regularly, remove the residual baits, excrement and other dirt on the bottom of the tank regularly to ensure the fresh water quality and clean the bottom of the pool. Ensure the quantity and quality of feeds and adjust the culture density of seedlings in time. Regular Quanchiposa disinfectants, probiotics, etc., ground observation, found that the disease should be diagnosed as soon as possible, find out the cause, the right medicine, and timely treatment.
Third, the test results
1. Hatching rate and survival rate of seedlings On July 13, 2004, 4.2 kg of fertilized eggs were collected from broodstock cages, and about 6 million larvae were hatched. The hatching rate was 75%. After 45 days of earth pond cultivation, a total of broilers were cultivated. There were 280,000 fry 3cm to 5cm in length, and the average survival rate was 4.67%.
2. Growth and development of larvae, juveniles and juveniles The newly hatched larvae have little activity. When quiescent, they usually lay on the water side, and the yolk sac is large. The oil globules are slightly in front of the yolk sac and the head is tightly attached to the yolk. Above the sac, the fins are transparent and connected together. The larvae are about 2mm in length. On the second day, the larvae had weaker activity and the organ differentiation was not obvious. On the third day, the larvae opened their mouths to feed and exercise was active. They could move up and down and touch the wall with their mouths. Black spots appeared on the eyes, and the dorsal, pectoral, and caudal fins were transparent. The total length was 2 mm to 3 mm. On the 6th day, the larvae had a total length of 3.2 mm to 3.4 mm, and the yolk and oil globules were completely absorbed. On the 15th day, pectoral fins, dorsal fins and anal fins were formed. The larvae were about 0.8 cm in length. On the 20th day, the fry was about 1.6cm in total length. On the 30th day, a few squamas were formed on the front of the fry and entered the juvenile stage. The total length was 2 to 3 cm. On the 40th day, the upper and lower jaws were well developed and the fins were well developed. The appearance and color of the fish were similar to those of adult fish. The young fishes had a total length of 3 cm to 5 cm. On the 45th day, juveniles were 4 cm to 6 cm in length. The growth of red snapper seedlings was significantly faster than that of the earlier period. After about 20 days of culture, the fry began to grow significantly, with an average daily increase of 1.0 mm to 1.5 mm.
3. Economic Benefits The nursery pond has a total area of ​​about 12 mu, and the nursery time is 45 days. The total cost is 42200 yuan, including 40000 yuan for fertilized eggs, 0.18 million yuan for clear pond disinfection, 20 thousand yuan for feed, and 0.5 million yuan for personnel. The utility cost was RMB 0.64 million and other expenses were RMB 0.5 million. A total of 280,000 fry were cultivated. The specifications ranged from 3cm to 5cm in total length, the average unit price of fish fry was 0.3 yuan/tail, the total output value was 84,000 yuan, and the total profit was 41,800 yuan. The ratio is about 1:2.
IV. Discussion
1. The economic benefits of artificial breeding of red snapper earthworms are good. It is one of the better ways for the fishermen in the South to get rich, because they have a fast growth, low seedling investment, short production cycle and high return rate.
2. The use of large earthen pond nursery, soil pond area is generally 3 acres ~ 5 acres, water body, after the fertilizer water pond water environment is stable, is conducive to the growth of fry, and the fry developed fast growth, strong physique, strong ability to move, The quality of the fry is close to the fry caught in the natural sea area; the silt in the earthen pond is beneficial to the growth of all kinds of microbes. It is not only the food of the basic bait creature in the water body, but also the supplementary bait of the young fry, which reduces the feed amount of the feed and saves the feed. The cost and the cost of a large number of water changes, and the growth of microorganisms are conducive to the decomposition of various residues and excreta, improving the environment of aquaculture water bodies. In addition, the earthen pond nursery has the advantages of simple facilities, low nursery cost, simple technical operation, and easy promotion.
3. The problems that should be noticed in the nursery stocking of red snapper earthworms are: First, the intensive cultivation of broodstock. In order to ensure the quality of fish eggs and improve the survival rate of broodstock, the broodstock should be fortified, and the puffer fish should be regularly fed with squid rich in unsaturated fatty acids, and squid powder and vitamin E should be used for feeding. The second is the feeding of feedstuffs. With domestication. According to the growth needs of fry, timely feeding of nutritious and palatable food organisms is the key to successful seedlings. Different growth stages of the red snapper fish fry require different feeds, and properly arrange and transition the good quality food organisms. It is beneficial to the healthy growth of fry, but also to avoid the mutual killing of fry due to the large differences in growth individuals. In general, 15 days before nursery, rotifer feeding was the main method, and 15 to 25 days of nursery seedlings were mainly fed with coccoids; after 25 days of nursery, fish and compound feed were mainly used. Between the phases, attention should be paid to the transition. On the 8th day, copepods and Artemia are started to be fed, and the amount of feeding is gradually increased, whereas the rotifers are on the contrary. On the 20th day, appropriate amount of fish gizzards and compound feeds were started, and oyster reptile larvae were better as an open bait when conditions were met. Third, screening was performed in time. The carp and the grouper share the same killing phenomenon. Therefore, timely screening is the key to the artificial breeding technology of the snapper. In the actual breeding process, the first sub-screening is generally performed in 25 days or so, and the sub-pool culture is adopted, while the premature sub-screening results in a small fry and low resistance, and is likely to die due to mechanical damage. Afterwards, according to the growth of fry, fish screens of the corresponding meshes are selected for repeated screening, so as to reduce the differences among individuals, reduce the occurrence of mutual disability, accelerate the growth of seedlings and increase the survival rate; and fourth, the seedling density. The appropriate stocking density is an important factor to achieve a better survival rate of seedlings. The stocking density should be adjusted in time according to the growth of fry. Early larval stocking density is too high, often due to overfeeding of food organisms affect the pond in the late food density, thus affecting the survival rate of nursery. Juvenile fish and juveniles have high stocking densities, which often reduce the dissolved oxygen content of the water, increase the differences between individuals, exacerbate the occurrence of mutual disability, and affect the survival rate of seedlings.
Author: Hainan University Oceanography
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