Grouper belongs to Perciformes, Grouper and Grouper in fish classification, so it is named because of its special stripes and markings. It is a bottom fish of islands and reefs, mainly distributed in the East China Sea and South China Sea of China, and grouper is one of the precious seafood. Generally, it is 7 ~ 15 cm long and brown, and there are 6 brown horizontal bands on its side, which are arranged neatly, and the width of the bands is greater than the distance between the two bands. Dorsal fin1; The caudal fin is fan-shaped, with many irregular black spots, the dorsal fin is white, and the gluteal fin is yellowish. Its tender meat, delicious taste, rich nutrition, high local price, long-standing reputation in domestic and foreign markets, short supply, exported to Hong Kong, Macao, Southeast Asia and Japan. The common species along the coast are jewel grouper, six-band grouper, moire grouper, green grouper, vertical grouper, red grouper and salmon grouper.

First, living habits

Grouper is a kind of warm-water pelagic fish along the coast, mainly inhabiting rocks, submarine caves and crevice coral reefs. Generally, it does not form a large group, has a fierce temperament, is a carnivorous fish, and has cannibalism. Especially in the larval stage, the small ones are often swallowed by the big ones. The food is mainly crustaceans such as shrimp and crabs, followed by fish and mollusks. Grouper is hermaphrodite. As an individual grows, it can change sexually. Generally, females come first, then males, so it is difficult to distinguish between males and females until the gonads are mature. Spawning begins in March every year, which has the characteristics of multiple spawning. According to research and observation, there are two peaks in the feeding cycle of grouper. The first peak appeared in May in spring, and the second peak appeared after August in autumn.

Second, the growth analysis

According to the experiment, when the water temperature is between 22-30℃, the grouper is active, takes a large amount of food and grows fast. When the water temperature drops below 22℃ and above 19℃, it is the second. When the water temperature drops below 19℃, the food intake decreases obviously, the growth rate slows down, and the activity weakens with the decrease of water temperature. It is also observed that when the water temperature drops below 65438 00℃, the dead bait is no longer eaten, but the live crustaceans can still eat selectively. When the water temperature drops below 7.5℃, the fish will stop eating and stay still. When the water temperature is lower than 5.5℃, it dies. It has a wide adaptation range to salinity, and can survive in the range of 1 1‰-4 1‰, with an optimum of about 30‰.

Third, the growth period

May ~ 165438+ 10 in Zhejiang and Fujian coastal areas, April ~ 165438+ 10 in Guangdong and Guangxi coastal areas, and March ~ 65438+February in Hainan. Grouper grows from body length 10 cm to commercial fish weight of 500 g ~ 750 g 16 months ~ 24 months, and can be produced in two kinds of culture cycles. One is to put fish with a body length of 10cm in March-May of the first year, raise them in winter, and overwinter in a cage until they are put on the market before the next winter. The other is to release 200-gram large fish species from March to May, and raise them to 500 to 700 grams before winter, or to about 1.5 kg before winter in the following year. The growth rate of red grouper and salmon is slower than that of green grouper and spotted grouper, so the market specifications of green grouper and spotted grouper are larger.

Four, aquaculture technology and management measures

1, fry selection.

Pay attention to the quality of fish when choosing. Fish with strong body, strong vitality, no disease, no scale injury and good skin luster should be selected for breeding. There are two main ways to cultivate adult grouper: cage culture and pond culture, and cage culture is more common. Cage culture of grouper is an intensive culture mode, which has high stocking density, convenient management and high production efficiency, so it has developed rapidly. When introducing adult fish culture technology, cage culture is the main method, and cage culture can be used as reference for pond culture and indoor cement pond culture.

2. Breeding conditions

The environment of the culture area should meet the following conditions: good shelter from the wind, small waves and no typhoon attack; Sandy bottom, gravel bottom and rock bottom are better, and the water depth should be more than 4 meters at low tide; The tidal current is gentle and the velocity is moderate, and the velocity in the cage should be kept at 0.20 m/s ~ 0.75 m/s; The lowest water temperature in winter shall not be lower than 15℃, and the water temperature from 22℃ to 28℃ shall not be lower than 200 days; The water quality is fresh, and the grouper can adapt to a wide range of salinity, and can survive between 1 1‰-4 1‰. The optimum salinity is 25-32 ‰, pH is 7-9, and the dissolved oxygen is above 5 mg/L; There is no pollution from industrial and agricultural wastewater and urban sewage, and there is no large amount of fresh water flowing out during the rainstorm season. The salinity is not lower than 16, and the transparency is above1.5m. The traffic conditions are good, and the live fish transportation and feed supply are convenient.

At present, the culture of grouper has not reached the production requirements, so the cultured fish are still cultured with young fish caught in natural sea areas as fry. It is best to catch young groupers by hand. Pay attention to the quality of fish when choosing. Fish with strong body, strong vitality, no disease, no scale injury and good skin luster should be selected for breeding.

3, stocking specifications and density

The stocking density has a great relationship with the flow velocity in the aquaculture sea area, and the sea area with stable flow velocity can be larger, and vice versa. Generally, a 3×3×3 (meter) cage can hold about 2,500 fish in each box with specifications below 50g/ piece, and about 2,500 fish in each box with specifications below 1.50g/ piece. That is to say, the yield of 3×3×3 (m) cage culture of about 200 kg is more suitable. The stocking density of grouper cultured in sea cage is 60 ~ 70 fish /m3 at 25℃. In production practice, about 500 adult fish were raised in 3 m× 3 m× 3 m cages. The results showed that when the stocking density was 65438 0.5 and 30 fish /m3, the growth rate of grouper was faster, and when the stocking density was increased to 60 fish /m3, the growth rate of grouper was similar to the former, with no obvious difference. However, when the stocking density increased to 120 fish /m3, the tail weight gain decreased, the feed coefficient increased greatly, and the survival rate decreased obviously. It is proved that the stocking density of adult fish is 60 per cubic meter. Red-spotted grouper was cultured in cages in Xiangshan Port, Zhejiang Province, and the stocking density of 100g ~ 150g was 90 ~ 70 /m2.

4, feed and feeding technology

Grouper is a carnivorous fish, and the main feed is small miscellaneous fish with high freshness. Generally, according to the size of grouper, small miscellaneous fish are cut into appropriate sizes with a fish cutter and then fed. Due to the different species of feed fish, the feeding coefficient fluctuates between 5 ~ 12. As feed, the feeding coefficient of blue round fish ginseng is low, while that of eye fish is high. With the rapid development of cage culture of grouper, the supply of feed fish is increasingly tight, so it is imperative to popularize artificial compound feed for grouper. Practice shows that grouper has high requirements for palatability of feed, such as hardness, color and taste. It likes to eat soft granules, light and bright feed, but if the granules are too hard, it will vomit. Its adaptability to soft pellet feed is obviously better than that of hard pellet feed. There is a long adaptation process from feeding small miscellaneous fish to feeding artificial compound feed, and feeding and domestication should be carried out before feeding compound feed. The suitable content of crude protein in artificial compound feed for red-spotted grouper is 40% ~ 50%; The suitable content of protein in compound feed for grouper is 5 1% ~ 55%, and the suitable content of fat is about 9.87%. If the fat content in the feed is properly increased, more protein can be used for fish growth instead of being consumed as an energy substance, which can save protein and improve the utilization rate of feed protein. Fish meal, as the main protein feed for salmon grouper and fry, grows best when the protein content is 40% ~ 50% and 54% respectively. Salmon and grouper were fed with dry compound feed made of fish meal and casein, and the optimum content of protein was 50%. The amino acid composition of grouper muscle has little difference among species. 10 the essential amino acid composition pattern is lysine: leucine: arginine: valine: threonine: isoleucine: phenylalanine: methionine: histidine: tryptophan = 9.8: 9.1:7.7: 5.2: 5.0: 4.9: 4.8: 3.66. The amino acid composition model can provide reference for the allocation of compound feed for grouper. The electrophysiological thresholds of red grouper and green grouper to alanine stimulation were 10 mol/L ~ 9.9 mol/L and 10 mol/L ~ 9.6 mol/L, respectively, which were significantly lower than those of other fish. This may be related to the fact that they live between rocks at the bottom, their visual function is degraded and their olfactory function is relatively developed. This provides a good prospect for the study of olfactory attractant for grouper. Grouper has special requirements for feed granularity. When feeding adult fish, the particle size of granular feed should not be less than 6 mm, the particles are too small and the appetite is not high.

Feeding technology has great influence on the culture effect of grouper. Under the environmental condition of water temperature of 25℃, the digestion speed of grouper is about 20 ~ 24 hours. Therefore, the grouper is fed once a day in the South China Sea from May to 10, usually from 9 am to 1 1. 165438+ 10 ~ 65438+February and March ~ April, once every two days, and once every three to four days when the seawater temperature drops below 20℃ in winter. Each feeding amount accounts for about 3% ~ 5% of body weight. When the water temperature is suitable, the feeding amount is large, and when the water temperature is too low or too high, the feeding amount is reduced. In production, the feeding amount is generally determined according to the feeding state of grouper, and the degree is when the appetite is weakened. The general principle of feeding is small tide, slow flow and clear water. When the water temperature is suitable, feed more and feed less. Generally, the daily feeding amount is about 8% of the fish weight. When feeding each time, it should be put into Jamlom and sprayed slowly in batches. After grabbing the first batch of feed, sow the next batch until the feed is full. Never pour the feed into the cage at one time, so as not to waste the feed and pollute the environment. Groupers will never eat food that sinks to the bottom. Because groupers eat by swallowing, the individual size of the bait is smaller than the diameter of the fish. Feeding should also pay attention to the principles of qualitative, quantitative and timing. In pond culture, attention should also be paid to setting up feed tables and feeding at fixed points in order to improve the utilization rate of feed, facilitate the cleaning of residual materials and maintain good water quality.

5, grading feeding

Fish should be graded according to their size. In theory, the smaller the individual difference, the better, but it is difficult to do it in practice. Because of the small difference in fish size, the fish feed evenly, which is beneficial to growth.

6. Daily management

Choose cages and fish rafts with reasonable density to prevent hypoxia accidents. In the process of culture, besides feeding, we should always observe and check the growth, food intake, activity and body color of fish, and also regularly check whether the cage is damaged and the number of attached organisms, and regularly remove the fouling organisms attached to the cage to keep the water flow inside and outside the cage smooth. It can be removed by preventive agents, mechanical cleaning and chemical treatment, and feeding natural enemies of fouling organisms. Screening regularly, put the groupers of the same size in the same cage. Because fish will overwhelm the growth of small fish when they are hungry, they will kill each other, so they should be screened regularly to make the grouper in the cage uniform in size. A small number of Sparidae and omnivorous fish are mixed. In this way, firstly, the bottom leftovers and fouling organisms on the cage can be removed; Second, because the Sparidae fish are predatory, it can stimulate the appetite of groupers; Third, it can make full use of water space and feed resources to improve the efficiency of aquaculture. Reinforce iron anchors and anchor cables, and regularly check the damage of cages to ensure safety in production. Especially before the arrival of the typhoon, it is necessary to strengthen defense, strengthen anti-storm measures, do a good job in safety and ensure production safety. Regularly monitor the water quality to protect the breeding environment. Monitoring aquaculture water according to the first-class seawater quality standards promulgated by the state is beneficial to the normal growth and delicious meat quality of groupers and prevents accidents caused by water quality deterioration.

Verb (abbreviation for verb) disease control

In daily management, we should pay great attention to nutrition balance, fresh water quality and disinfection; Once a disease is found, it should be actively treated and isolated to prevent the spread of pathogens.

1, parasitic diseases

① Irregular white spots (also called valve lesions) appear on the body surface of leukoplakia. In severe cases, the leukoplakia expands into blocks, and the mucus on the surface of head, skin, fins and cheeks increases obviously, resulting in slow swimming and difficulty breathing. After death, the pectoral fins are stiff and almost close to the buccal lid. The pathogen is grouper, which is parasitic on the gills, body surface and fins of grouper akasaka. Soak in 2× 10-6 concentration copper sulfate seawater solution for 2 hours, repeat the next day, and the curative effect is remarkable. Or bathing in fresh water for 4 minutes can also kill grouper valve worms and treat white spot disease.

② White spots with a diameter of 0.5 mm ~ 1 mm appeared on the fish with white spot disease (also known as small melon disease), with increased mucus, scales falling off and anorexia. Small melon worms parasitize and destroy small gills, causing fish to have difficulty breathing until they die. When the water temperature is about 30℃, the white spot disease spreads quickly, and the grouper in the whole cage or fish pond will be infected within a few days. The pathogen is Cryptosporidium irritans. Soak in fresh water for 5 minutes to 10 minute, or bathe in formaldehyde seawater with the concentration of 1 00x10-6 for 30 minutes to1hour, once every 3 to 5 days.

③ The fish with rotational disease (also known as myxosporiasis) swims abnormally on the sea surface and cannot enter the deep water layer. The pathogen is brain mucus. The prevention method is to use 0.34× 10-6 potassium permanganate medicated bath 10 minute to keep the water fresh.

④ The fish with dactylosis lose luster, lose appetite and swim slowly. Some fins fester, mucus on the body surface and cheeks increases, local scales fall off, one or two eyeballs protrude, become inflamed, die or fall off, swimming loses balance and turns around. The pathogen is Dactylogyrus. Soak in clear water for 5 minutes ~ 10 minute, once a day for 2 ~ 3 days, and the curative effect is good.

⑤. When the metacercariae of trematodes proliferate in large quantities, it can cause the sick fish to swim slowly, the mucus on the gills increases, some gills are congested, and some gills are reddish. In severe cases, people will die of dyspnea. Pathogenic organisms include Paragonimus grouper, Diptera armyworm and Diptera grouper. For treatment, please refer to finger disease.

⑥. Cryptosporidiosis is similar to trematode, and the pathogen is Cryptosporidiosis, which can be killed by soaking in fresh water or potassium permanganate solution with concentration of 0. 15× 10-6 for 5 minutes.

⑦. Ill mullet parasitizes on the fish's body surface and gills, and sucks nutrients from the fish with suction cups, which destroys the integrity and respiratory function of gills and eventually leads to the death of the sick fish. Sole fish breed and spread quickly, especially in the season of high seawater temperature. At present, there is no effective treatment method that does not pollute the environment, and attention should be paid to keeping the water clean in aquaculture production, which can effectively prevent the occurrence of the disease.

Adding parasites such as algae, trypanosoma, cercospora and rotifer to starch eggs is also harmful to grouper. In addition, nematodiasis is a common parasitic disease of grouper, with a high infection rate. Especially in cage culture, the nematode infection of feed fish to grouper is very serious. Sometimes dozens of them appear in the body cavity, which is ignored because the symptoms are not obvious.

2. Bacterial diseases

① The tail of rotten tail disease is congested and inflamed, the skin is ulcerated and scales fall off. The edge of the fish focus is bloodshot and red, and the center is swollen and ulcerated. In severe cases, the muscles and bones are exposed, and the fish loses its balance and dies for dozens of days. Most of them occur from April to 10, and the mortality rate is very high. Prevention can be done with 0.34× 10-6 potassium permanganate bath 10 minute, and antibiotics can also be used to relieve the disease.

The main symptoms of canker fish are slow movement, swimming out of the water, ulcers on fins and bases, and even bruises all over the body. Ulcer surfaces vary in size and shape. The ulceration surface will deepen and eventually die, with a high mortality rate. The pathogen is Vibrio vulnificus. The onset season is from April to 1 1. Soak in nitrofurazone for 3 ~ 5 minutes, and take antibiotics orally to control the disease. Using formalin inactivated vaccine, heat inactivated vaccine and crude lipopolysaccharide extracted from Vibrio vulnificus, the green grouper and salmon grouper obtained good immune protection through intramuscular injection.

③ Fingerprint erythema initially appeared on both sides of the fish with bacterial white spot disease, and in a few cases, it could appear on the head and tail, and the focus was slightly raised. With the development of the disease, the lesion turns into leukoplakia, at which time the scales are slightly upright and easy to fall off. The white spots are clearer after the scales fall off. Sick fish have poor appetite, and the mortality rate is as high as 90%, which is prevalent in winter. The preventive measure is to avoid fish injury. Antibiotics and anti-inflammatory drugs can alleviate the disease, but the effect is not obvious.

3. Other diseases

① The swim bladder of malnutrition syndrome swells, the abdomen swells, loses balance, and spins on the water surface or the bottom of the cage, so it is commonly known as "distension disease" and "rotation disease". Tissue sections showed fatty degeneration, necrosis, vacuolation and nuclear lysis of the liver. Ill fish have local or systemic inflammation in gills and viscera, and die after floating on the water for several days, with high mortality. From May to 10 epidemic season, the drug "Qingzhangning" was used for prevention and control, and the effect was good.

② The fish with proliferative nephropathy have different degrees of abdominal distension, hanging upside down or lying on their side, the fins and body surface are ulcerated, one or two eyeballs are prominent, blind or limping, and the body surface is black or white, which is a serious epidemic "puffiness" in grouper culture. The average white blood cells accounted for 48.09% and monocytes accounted for 2.82%, which was significantly higher than the normal value. The pathogen is a kind of protozoan myxomycetes with high incidence. Yu Bao Powder, a drug developed by Nanhai Fisheries Research Institute of Chinese Academy of Fishery Sciences, has achieved remarkable results.