Culture techniques of grouper

Grouper is a Perciformes, body length slightly elliptical side flat, large mouth, with auxiliary maxilla, teeth pointed, and some expanded into canine teeth. The body is covered with small ctenoid scales, sometimes buried under the skin. Dorsal and anal spines developed. Caudal fin rounded or concave. Body color variation is many, often brown or red, and with stripes and spots, warm water for large and medium-sized marine fish. Grouper nutrient-rich, tender white meat, similar to chicken, known as "sea chicken" said. Grouper is also a low-fat, high-protein high-grade food fish, Hong Kong and Macao region was pushed for one of China's four famous fish, is an essential high-end feast dishes.

seedling selection

When choosing, you must pay attention to the quality of the fish. Fish should be selected strong, vigorous, disease-free, no scale damage, skin luster good breeding.

There are two main ways of grouper adult fish culture: cage culture and pond culture. Cage culture is more common. Cage culture of grouper is an intensive culture method, with high stocking density, easy management and high production efficiency, so it develops rapidly. Cage culture is the main technique in introducing adult fish culture. Cage culture can be referred to for pond culture and indoor cement pond culture.

breeding conditions

The environment of culture sea area shall meet the following conditions: good wind protection conditions, small waves, no typhoon attack; sandy bottom, gravel bottom and reef bottom are good, and the water depth shall be more than 4 meters at low tide; the tide is smooth, the flow velocity is moderate, and the flow velocity in the cage shall be maintained at 0.20 m/s ~0.75 m/s; the minimum water temperature in winter shall not be lower than 15℃, and the water temperature days of 22℃~28℃ shall not be less than 200 days; The water quality is fresh, the grouper can adapt to a wide range of salinity, and can survive between 11‰ and 41 ‰, and the most suitable salinity is 25~32‰, pH=7~9, dissolved oxygen is above 5 mg/L; it is not polluted by industrial and agricultural wastewater and urban sewage; there is no large amount of fresh water inflow in rainstorm season, the salinity is not lower than 16, and the transparency is above 1.5 meters; the traffic conditions are good, and the live fish transportation and feed supply are convenient.

At present, grouper breeding has not yet reached the production requirements, so the cultured fish are still caught in the natural sea area of juvenile fish for fry cultivation. Cultured grouper juveniles are better caught by hand. When choosing, you must pay attention to the quality of the fish. Fish should be selected strong, vigorous, disease-free, no scale damage, skin luster good breeding.

stocking specification and density

The stocking density has a great relationship with the flow velocity of the culture sea area. The flow velocity of the culture sea area can be larger, and vice versa. Generally, a cage of 3×3×3(m) can put about 2500 fish in each box with the specification of 50 g/tail, and about 1000 fish in each box with the specification of 150 g/tail.

That is to say, a 3×3×3(m) cage culture yield of about 200 kg is more appropriate. The stocking density of grouper in marine cage culture is 60 ~70 fish/m3 at 25℃. In production practice, about 500 adult fish were raised in a cage of 3 m × 3 m ×3 m. The results showed that grouper grew faster when stocking density was 15 and 30 individuals/m3, and the growth rate was similar to that of grouper when stocking density was increased to 60 individuals/m3. However, when stocking density increased to 120 fish/m3, the weight gain of fish decreased, feed coefficient increased greatly, and survival rate decreased significantly. It was proved that stocking density of 60 fish/cubic meter was suitable. The suitable stocking density of Epinephelus rubriflatus in cage culture in Xiangshan Harbor is 90 ~70 fish/m2, tail weight 100 ~150 g.

Feed and feeding techniques

Grouper is a carnivorous fish. The main feed used is small miscellaneous fish with high freshness. Generally according to the size of grouper, fish cutting machine will be used to cut small miscellaneous fish feeding appropriate size. The feeding coefficient fluctuated between 5 and 12 due to different species of forage fish. The feeding coefficient of blue roundfish was lower than that of eye fish. With the rapid development of grouper cage culture industry, the supply of feed fish is increasingly tight, and it is imperative to promote artificial feed to feed grouper.

The practice shows that grouper has higher requirements on the palatability of feed, such as hardness, color and taste. It likes to eat soft pellets, light color and bright feed, and has vomiting phenomenon when the pellets are too hard. Its adaptability to soft pellets is obviously better than hard pellets. There is a long adaptation process from feeding small fish to feeding artificial compound feed, and feeding domestication should be carried out before feeding compound feed. The optimum crude protein content in artificial feed for red grouper is 40%~50%, the optimum protein content in artificial feed for blue grouper is 51%~55%, and the optimum fat content is about 9.87%. If the fat content in the feed is properly increased, more protein can be used for the growth of fish, and it will not be consumed as an energy substance, which can save protein and improve the utilization rate of feed protein.

Salmon grouper and fry were fed with wet pellet diet containing fish meal as main protein. The fish grew best when the protein content was 40%~50% and 54%, respectively. Salmon grouper was fed with dry compound feed made of fish meal and casein, the optimum protein content was 50%. The amino acid composition of grouper muscle showed little interspecific variation. The composition pattern of 10 essential amino acids was lysine: leucine: arginine: valine: threonine: isoleucine: phenylalanine: methionine: histidine: tryptophan =9.8∶9.1∶7.7∶5.2∶5.0∶4.9∶4.8∶3.1∶2.6∶1.0. This amino acid composition pattern can provide reference for formula feed configuration of grouper. The electrophysiological thresholds of red grouper and blue 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 their living in the bottom rocks, their visual function is degraded and their olfactory function is relatively developed. It provides a good prospect for the study of olfactory attractants of grouper. Groupers have special requirements for feed particle size. When feeding adult fish, the particle size of pellet feed should not be less than 6 mm, and the appetite is not high if the particle size is too small.

Feeding technology has great influence on grouper culture. Under the environmental condition of water temperature of 25℃, the digestion rate of grouper is about 20 hours to 24 hours. Therefore, grouper was fed once a day from May to October in the South China Sea, generally from 9:00 a.m. to 11:00 a.m. In November ~ December and March ~ April, the feed was once every two days, and in winter, the feed was once every 3 ~4 days when the seawater temperature dropped below 20℃. Each feeding amount accounts for about 3%~5% of body weight. When the water temperature is suitable, the feeding amount is larger, and when the water temperature is low or too high, the feeding amount is reduced.

During production, feeding is generally determined by the feeding status of groupers, with appetite reduced as the degree. The general principle of feeding is that the neap tide flow is slow and clear, and the water temperature is suitable. Daily feeding amount is generally controlled at about 8% of fish weight, each time feeding, should be put into a small Xu, slowly spread in batches, such as the end of the previous batch of feed, then sprinkle a batch until the feed is full, never pour feed into the cage at a time, so as not to cause feed waste and pollution of the environment, grouper never eat food at the bottom. Because groupers eat by swallowing, the individual size of the bait should be smaller than the caliber of the fish. Feeding should also pay attention to quality, quantity, timing principles. In pond culture, we should also pay attention to setting up feed platform and feeding at fixed points to improve the utilization rate of feed and facilitate the cleaning of residues and maintain good water quality.

Graded feeding

Fish species stocking should be based on the size of the sub-grade feeding. Theoretically, the smaller the individual difference, the better, but it is difficult to achieve practical operation. Due to the small difference in fish size, uniform feeding is conducive to growth.

daily management

Choose reasonable net cage and fish density to prevent anoxia accident. In addition to feeding, the growth, feeding, activity and body color of fish should be observed and inspected frequently during the breeding process. It is also necessary to check whether the cage is damaged and how many attached organisms are attached. The fouling organisms attached to the cage should be removed regularly to keep the water flow inside and outside the cage smooth. Fouling organisms can be removed by preventive agents, mechanical cleaning and chemical treatment, and by breeding natural enemies of fouling organisms. Regular screening to keep grouper body size consistent in the same cage. Because fish have the effect of big fish overwhelming small fish growth and self-cannibalism phenomenon when hungry, it should be screened regularly to make the size of grouper in the cage uniform.

Mixed culture of a small number of bream fish and omnivorous fish, such that:

① It can remove the bottom food residue and fouling organisms on the cage.

② Because of the strong eating habits of Sparidae fish, it can stimulate the appetite of groupers.

(3) It can make full use of water space and feed resources and improve breeding efficiency.

Reinforce the anchor and cable, regularly check the damage of the cage to ensure safe production. Especially before the arrival of typhoon, we should strengthen defense, strengthen anti-wind and wave measures, do a good job in safety work, and ensure production safety. Regularly monitor water quality and protect the breeding environment. According to the first class seawater quality standard issued by the state to monitor aquaculture water, conducive to the normal growth of grouper and fresh meat, prevent accidents caused by deterioration of water quality.