CATDOLL : CATDOLL: What are the techniques for grouper culture in earthen ponds? How should daily management be carried out?

1. What are the techniques for grouper culture in earthen ponds? How should daily management be carried out?

Grouper is delicious and colorful, and is loved by consumers everywhere. At present, my country generally cultivates it in cages. With the changes in the marine environment, cage cultivation is prone to many diseases. Therefore, it is very meaningful to promote grouper cultivation in earthen ponds.

1. Pond selection and dredging

1. Pond selection

The pond area is 5-20 mu, a total of 300 mu, and the pond depth is 2-6 meters; the bottom is sandy or gravel; it is easy to absorb tides, the water quality is fresh, there is no domestic and industrial pollution, and the maximum daily water exchange volume can reach 50%.

2. Clean the pool and remove toxins

Two months before stocking, drain the pond, dry the pond for two weeks, and remove silt and impurities from the surface of the pond; use stone slabs or stones to set up artificial fish reefs in deep water areas; install a filter net, let in 50 cm of water, apply 150 kg of quicklime per mu for soaking and disinfection for 15 days to kill pathogens and harmful organisms, and flush the pond twice.

2. Basic bait cultivation

20 days before stocking, add water to a depth of 0.4 cm, apply 500 grams of urea, 50 grams of superphosphate and 25 grams of silicate per mu for 3 consecutive times to make the water color yellow-green. Then gradually add water to 1 meter, and the transparency should be maintained at about 0.4 meters.

3. Seedling placement

All grouper fry are natural fry caught in this sea area. The fry purchased are caged or caught by fishing. When purchasing fry caught by fishing, fry with hook wounds or swallowed hooks should be discarded. The fry specifications are related to the time of seeding. The fry released in April weighs about 50 grams each, and the fry released in June weighs about 100 grams each. The seeding density is controlled within 667 fry/mu.

4. Feeding

The feed is mainly fresh small fish and shrimp. When fresh feed is insufficient, compound feed is fed. Feed once in the morning and evening every day. Feed less or not when the water temperature is below 13℃, and do not feed in the winter. The daily feeding amount is 8%-10% of the fish weight in the early stage, and 5%-6% in the middle and late stages. The specific feeding amount is adjusted according to the weather, water quality, feeding situation, the amount of residual bait, etc. Generally, the feeding situation is checked through the set feeding frame, and the principle is to finish feeding within 2 hours. Feed twice at 6 am and 5 pm. The feeding site is changed every 10 days to avoid the deterioration of local bottom quality and the impact on water quality due to long-term feeding.

5. Water quality management and disease prevention

1. Water quality control

Regularly test the physical and chemical factors of water quality. By changing water and sprinkling quicklime, the transparency is maintained in the range of 0.3-0.5 meters, the pH value is 7.8-8.5, the dissolved oxygen is above 5.0 mg/L, the ammonia nitrogen content is controlled below 0.5 mg/L, and the daily water change volume is about 30%. In the hot season, the water change time is arranged in the evening or dawn according to the tidal conditions, and drainage is avoided at noon as much as possible.

2. Disease prevention

Disinfect the pond water once a month with 0.3-0.5 g/cubic meter of Fish and Worm Net to kill parasites; disinfect the pond water once every half a month with 25 g/cubic meter of quicklime or 0.3-0.5 g/cubic meter of Sandai Fish and Shrimp An to kill pathogens; in summer, feed a course of oxytetracycline or allicin bait every month to prevent the occurrence of diseases.

The bottom of the breeding pond is preferably sandy or sandy muddy, with an area of ​​3 to 5 mu, a water depth of more than 1.5 meters, sufficient water source, fresh water without pollution, convenient inlet and outlet, the optimum water temperature is 22 to 30℃, the optimum salinity is 25 to 35, and one aerator should be equipped for every 2 mu of pond. U-shaped cement troughs, hollow cement bricks, plastic pipe sections with a diameter of 15 cm, and waste car tires are set at the bottom of the pond as artificial reefs to adapt to the habit of groupers to drill holes, while reducing the gathering of fish and cannibalism. The purpose of pond cleaning is to eliminate hidden dangers, which is the basis of healthy breeding and plays a key role in the survival rate and growth of seedlings.

When raising grouper, attention should be paid to the selection and dredging of the breeding pond. The pond area should be about 5-20 acres, the pond depth should be 2-6 meters, it must be easy to receive tides, the water quality must be fresh, and there must be no domestic and industrial pollution.

The stocking density is closely related to the flow rate of the aquaculture sea area. In the sea area with smooth flow rate, the stocking density can be larger, but in contrast, the stocking density can be smaller. Generally, a 3×3×3 (m) net cage can hold about 2,500 fish of a size below 50 grams per fish, and about 1,000 fish of a size below 150 grams per fish. In other words, a 3×3×3 (m) net cage with a production of about 200 kilograms is more appropriate.

2. Do you need to add salt when steaming grouper?

Don't! Instead of adding salt, pour a thin layer of steamed fish sauce on the steam before serving. Believe me, it will be very fresh and tasty.

3. How many times can a grouper change gender per day at most?

Groupers can change sex up to ten times a day.

Groupers are hermaphrodites with sex-changing characteristics. When they first reach sexual maturity, all are female, and they change into males the following year. Therefore, there are significantly fewer males than females.

The salmon grouper is a batch spawning type. There are oocytes of different phases in the same ovary. Even in the mature ovaries in the 5th stage of spawning, there are many oocytes in the 3rd and 4th phases, and there is no sign of degeneration, indicating that the development of oocytes is asynchronous. When the environmental conditions are suitable, the oocytes can still develop to maturity, and the eggs can mature and be produced in batches during a reproductive cycle. The red-spotted grouper is a one-time spawning type, but in the reproductive season, the sexual maturity and reproduction of individuals are different. The first mature individuals reproduce early, and the later mature individuals reproduce late. However, it has been observed that the entire spawning cycle of the red-spotted grouper can last for 2 to 3 months, which is divided into three stages: the early stage, the middle stage and the late stage. Each stage spawns multiple times continuously. The middle stage is the peak spawning period, and the eggs produced account for more than half of the total number of eggs. The total number of eggs laid by grouper individuals ranges from 70,000 to more than 1 million, and large species have 10 million eggs.

Groupers live in tropical and temperate oceans. They like to live in the sea areas with rocky reefs, gravel and coral reefs near coastal islands. They usually do not live in groups. The water layer where they live rises and falls with the water temperature. In spring and summer, they are distributed in waters 10 to 30 meters deep, and in midsummer, they can also appear in waters 2 to 3 meters deep. In autumn and winter, when the water temperature drops, they swim to deeper waters of 40 to 80 meters. The suitable temperature range is 15 to 34 degrees Celsius, and the most suitable water temperature is 22 to 28 degrees Celsius. The suitable salt range is wide, and they can survive in seas with salinity above 10‰.

Grouper has medicinal value of strengthening the spleen and replenishing qi.

Because grouper often preys on fish, shrimps and crabs, they will also ingest astaxanthin, which is rich in shrimps and crabs. For humans, grouper becomes a food containing astaxanthin.

Astaxanthin (also known as astaxanthin in Japan, Hong Kong and Macau) is a super strong natural extracellular antioxidant first isolated from lobster in 1938. It is also the only antioxidant that can delay the aging of organs and tissues. Grouper also contains astaxanthin. The important nutrient substance of grouper skin colloid that enhances the complete growth of epithelial tissue and promotes the synthesis of collagen cells is called dimethyl sulfone (MSM); and "collagen" is high in fat and easily oxidized, so it must be used with antioxidants to achieve the effect of beauty and skin care. Because grouper has both dimethyl sulfone (MSM) and astaxanthin, it has the title of "beauty and skin care fish".