CATDOLL : CATDOLL: What should I feed freshwater grouper?

What should I feed freshwater grouper?

Freshwater groupers feed on animal feed all their lives, from larvae to adults. Research on the feed series of artificially cultivated blue grouper fry and juveniles shows that after the fry open their mouths, they feed on fertilized eggs of bivalves, trochophore larvae and veliger larvae, and then switch to rotifers, cladocerans and copepods, and then switch to copepods, mysid shrimps and brine shrimps. During the juvenile stage, they begin to transition to feeding on small fish, small shrimps and cephalopods. Groupers have a ferocious feeding habit, and will eat any animal food, whether it is dead or alive. The fresher it is, the more they like to eat it, and they are extremely greedy. Their menu includes fish, shrimp, crab, mantis shrimp, cephalopods, sea urchins, brittle stars, barnacles, etc.

Seeking grouper breeding methods and pictures

Practical technology of grouper breeding

Grouper belongs to the order Perciformes, family L, genus Epinephelus in fish classification. It is named for the special stripes and patterns on its body. It is an island reef bottom fish. It is mainly distributed in the East China Sea and the South China Sea in my country. Grouper is one of the precious seafood. It is generally 7 to 15 cm long, brown in color, with 6 brown horizontal bands on the side of the body, arranged neatly between the bands, and the width of the band is greater than the distance between the two bands. There is one dorsal fin; the caudal fin is round and fan-shaped, with many irregular black spots, white dorsal fin, and light yellow anal fin. Its meat is tender, delicious, and nutritious. It is sold at a high price locally. It has a long-standing reputation in the domestic and foreign markets. It is in short supply and is exported to Hong Kong, Macao, Southeast Asia, and Japan. Common species along the coast include gem grouper, six-banded grouper, cloud grouper, blue grouper, longitudinal band grouper, red-spotted grouper, and salmon-spotted grouper.

1. Living habits

Grouper is a coastal warm-water mid-bottom layer fish, mainly living in rocky reef areas, seabed caves and coral reefs with gaps. Generally, it does not form large groups. It is a ferocious carnivorous fish and has the phenomenon of cannibalism. Especially in the juvenile stage, small individuals are often swallowed by large individuals. The food is mainly crustaceans such as shrimps and crabs, followed by fish and mollusks. Grouper is hermaphroditic. As the individual grows, it can undergo sexual transformation, generally first female and then male. Before the gonads are immature, it is difficult to distinguish between males and females. It starts to spawn from March every year, and has the characteristic of multiple spawning. According to research and observation, the feeding cycle of blue grouper has two peaks a year. The first peak occurs in May in spring, and the second peak occurs after August in autumn.

2. Growth Analysis

According to the test, when the water temperature is between 22-30℃, the blue grouper is active, eats a lot and grows fast; when the water temperature drops below 22℃ and above 19℃, the fish is second; when the water temperature drops below 19℃, the fish eats less food, grows slower, and the activity decreases as the water temperature drops; when the water temperature drops below 10℃ during wintering in indoor pools, it is also observed that the fish will no longer prey on dead bait, but will still choose to eat live crustaceans; when the water temperature drops below 7.5℃, the fish stop eating and remain motionless; when the water temperature is below 5.5℃, the fish die. The fish has a wide range of adaptability to salinity, and can survive between 11‰-41‰, with the most suitable being around 30‰.

3. Growth period

In the coastal areas of Zhejiang and Fujian, it is from May to November; in the coastal areas of Guangdong, Guangxi, Hong Kong and Taiwan, it is from April to November; in Hainan, it is from March to December. It takes 16 to 24 months for grouper to grow from a body length of 10 cm to a commercial fish weight of 500 to 750 grams. Two breeding cycles can be used to arrange production. One is to release 10 cm long fingerlings from March to May of the first year, raise them until winter, when the weight reaches 150 to 200 grams, overwinter in net cages, and keep them until they are put on the market before winter of the second year. The other is to release large-sized fingerlings weighing 200 grams from March to May, and raise them to 500 to 700 grams before winter, or raise them to about 1.5 kilograms before winter of the second year. The growth rate of red-spotted grouper and salmon-spotted grouper is slower than that of blue grouper and spotted grouper, so the market size of blue grouper and spotted grouper is larger.

4. Breeding techniques and management measures

1. Selection of fish fry.

When choosing, you must pay attention to the quality of the fish. You should choose fish that are strong, energetic, disease-free, scale-free, and have a good skin color for breeding. There are two main ways to breed adult groupers: cage breeding and pond breeding, with cage breeding being more common. Cage breeding of grouper is an intensive breeding method with high stocking density, easy management, and high production efficiency, so it has developed rapidly. When introducing adult fish breeding technology, cage breeding is the main method, and pond breeding and indoor cement pool breeding can refer to cage breeding.

2. Breeding conditions

The environment of the aquaculture sea area should meet the following conditions: good shelter from the wind, small waves, and not affected by typhoons; sandy, gravelly, and reef bottoms are preferred, and the water depth should be above 4 meters at low tide; the tide is smooth, the flow rate is moderate, and the flow rate in the cage is preferably maintained at 0.20 m/s to 0.75 m/s; the lowest water temperature in winter is not lower than 15°C, and the number of days with a water temperature of 22°C to 28°C is not less than 200 days; the water quality is fresh, and grouper has a wide range of adaptability to salinity and can survive between 11‰ and 41‰, the most suitable salinity is 25 to 32‰, pH = 7 to 9, and the dissolved oxygen content is above 5 mg/L; it is not polluted by industrial and agricultural wastewater and urban sewage, and there is no large amount of fresh water inflow during the rainy season, the salinity is not lower than 16, and the transparency is above 1.5 meters; the transportation conditions are good, and the transportation of live fish and the supply of feed are convenient.

At present, the breeding of grouper fry has not yet reached the production requirements, so the farmed fish are still raised from young fish caught in natural sea areas. It is better to catch the farmed grouper fry by hand fishing. When selecting, you must pay attention to the quality of the fish. You should choose fish that are strong, energetic, disease-free, scale-free, and have a good skin color for breeding.

3. Stocking specifications and density

The stocking density has a great relationship with the flow rate of the breeding sea area. The stocking density can be larger in the sea area with smooth flow rate, and vice versa. Generally, a 3×3×3 (meter) cage can hold about 2,500 fish species with a specification of less than 50 grams per fish, and about 1,000 fish species with a specification of less than 150 grams per fish. In other words, a 3×3×3 (meter) cage culture output of about 200 kilograms is more appropriate. The stocking density of seawater cage culture of grouper is preferably 60 to 70 per cubic meter under the condition of a water temperature of 25°C. In production practice, about 500 adult fish are raised in a 3m×3m×3m cage. The results show that the growth of grouper is faster when the stocking density is 15 and 30 per cubic meter. When the stocking density is increased to 60 per cubic meter, the growth rate is similar to the former, with no obvious difference. However, when the stocking density increased to 120 tails/m3, the weight gain of the tails decreased, the feed coefficient increased greatly, and the survival rate decreased significantly. It was proved that the stocking density of 60 tails/m3 for adult fish was more appropriate. In the cage culture of red-spotted grouper in the Xiangshan Port area of ​​Zhejiang Province, the stocking density of tails weighing 100g to 150g should be 90 tails/m2 to 70 tails/m2.

4. Feed and feeding technology

Grouper is a carnivorous fish, and the main feed for feeding is small fish with high freshness. Generally, according to the size of the grouper, the small fish are cut into appropriate sizes with a fish cutter before feeding. Due to different types of feed fish, the feeding coefficient fluctuates between 5 and 12. The feeding coefficient of blue round fish as feed is low, while the feeding coefficient of eye fish is high. With the rapid development of grouper cage farming, the supply of feed fish is becoming increasingly tight, and it is imperative to promote the feeding of grouper with artificial compound feed. Practice has shown that grouper has high requirements for the softness, hardness, color and taste of feed. It likes to eat soft particles, light-colored and bright feed. If the particles are too hard, it will spit out food. Its adaptability to soft granular feed is significantly better than that to hard granular feed. There is a long adaptation process from feeding small fish to feeding artificial compound feed. Feeding acclimatization should be carried out before feeding compound feed. The appropriate crude protein content in the artificial feed for red grouper is 40% to 50%; the appropriate protein content in the feed for blue grouper is 51% to 55%, and the appropriate fat content is about 9.87%. If the fat content in the feed is appropriately increased, more protein can be used for the growth of the fish body instead of being consumed as an energy substance, which can save protein and improve the utilization rate of feed protein. When the wet pellet feed prepared with fish meal as the main protein source is fed to salmon grouper fish and fry, the growth is best when the protein content is 40% to 50% and 54% respectively. When the dry compound feed is made with fish meal and casein as the protein source to feed salmon grouper, the optimal protein content is 50%. There is little interspecific variation in the amino acid composition of grouper muscle. The composition pattern of the 10 essential amino acids 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: 3.1: 2.6: 1.0. This amino acid composition pattern can provide a reference for the configuration of grouper compound feed. The electrophysiological thresholds of red-spotted grouper and blue grouper to alanine stimulation are 10 mol/L to 9.9 mol/L and 10 mol/L to 9.6 mol/L, respectively, which are significantly lower than those of other fish. This may be related to the fact that they live among the bottom reefs, their visual function is degraded, and their olfactory function is relatively developed. It provides a good prospect for the research of olfactory attractants for grouper. Grouper has special requirements for the size of feed particles. When feeding adult fish, the particle size of granular feed should not be less than 6 mm. If the particles are too small, the appetite will not be high.

Feeding technology has a great influence on the effect of grouper farming. Under the environmental condition of water temperature of 25℃, the digestion speed of grouper is about 20 hours to 24 hours. Therefore, in the South China Sea, grouper is fed once a day from May to October, generally between 9 am and 11 am. From November to December and March to April, it is fed once every two days. In winter, when the seawater temperature drops below 20℃, it is fed once every 3 to 4 days. The feeding amount each time accounts for about 3% to 5% of the 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. In production, the feeding amount is generally determined according to the feeding state of grouper, and the feeding amount is determined when the appetite decreases. The general principle of feeding is that when the water flow is slow and the water is clear during the tidal period, more feeding is required when the water temperature is suitable, and less feeding is required. The daily feeding amount is generally controlled at about 8% of the fish's body weight. Each time you feed, you should first put in a small amount and slowly sprinkle it in batches. After the fish have eaten up the previous batch of feed, sprinkle the next batch until they are full and no longer have to fight for food. Never dump the feed into the net cage at once to avoid feed waste and environmental pollution. Groupers never eat food that sinks to the bottom. Since 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 the principles of quality, quantity, and timing. In pond farming, you should also pay attention to setting up a feeding table and feeding at a fixed point to improve the utilization rate of feed and facilitate the cleaning of residual materials to maintain good water quality.

5. Feeding in different grades

When stocking fish, they should be raised in grades according to their size. Theoretically, the smaller the individual differences, the better, but it is difficult to achieve in practice. Because the size differences of fish are small, they feed evenly, which is conducive to growth.

6. Daily management

Choose a reasonable cage and fish row density to prevent hypoxia accidents. In addition to feeding, fish growth, feeding, activity and body color should be observed and checked frequently during the breeding process. The cages should also be checked for damage, the number of attached organisms, and the fouling organisms attached to the cages should be removed regularly to keep the water flow inside and outside the cages smooth. Fouling organism preventive agents, mechanical cleaning and chemical treatment, and natural enemies of fouling organisms can be used to remove them. Screen regularly to keep the size of grouper fish in the same cage consistent. Because fish have the effect of large fish overwhelming the growth of small fish and cannibalism when hungry, they should be screened regularly to make the size of grouper fish in the cage uniform. Mix a small amount of Sparidae and omnivorous fish. In this way, first, the bottom food residues and fouling organisms on the cages can be removed; second, because Sparidae have strong food-grabbing ability, they can stimulate the appetite of groupers; third, the water space and feed resources can be fully utilized to improve the breeding efficiency. Strengthen the anchors and cables, check the damage of the cages regularly, and ensure safe production. Especially before the arrival of a 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 aquaculture environment. Monitor aquaculture water according to the first-class seawater quality standards issued by the state, which is conducive to the normal growth of grouper and the delicious meat, and prevent accidents caused by water quality deterioration.

5. Disease prevention and control

In daily management, we must pay great attention to balanced nutrition, fresh water quality, and disinfection; once the disease is discovered, we must actively treat it, isolate it, and prevent the spread of pathogens.

1. Parasitic diseases

①. White spot disease (also called valvulariasis) Irregular white spots appear on the body surface. In severe cases, the white spots expand and become continuous. The mucus on the head, skin, fins and gills increases significantly. The fish swims slowly and has difficulty breathing. After death, the pectoral fins become stiff and almost close to the gill cover. The pathogen is grouper valvularia, which parasitizes on the gills, body surface and fins of red-spotted grouper. Soaking in a 2×10-6 concentration of copper sulfate seawater for 2 hours and repeating it the next day has a significant effect. Bathing in fresh water for 4 minutes can also kill grouper valvularia and treat white spot disease.

②. White spot disease (also called Ichthyophthirius punctatus) White spots with a diameter of 0.5 mm to 1 mm appear on the body surface of the diseased fish, mucus increases, scales fall off, and the fish loses its appetite. Ichthyophthirius punctatus parasitizes the gills and destroys the gills, causing breathing difficulties and even death. When the water temperature is around 30℃, white spot disease spreads quickly. Within a few days, the entire grouper in the net cage or fish pond will be infected. The pathogen is Cryptocaryon irritans. Soak in fresh water for 5 to 10 minutes, or use 100× 10-6 formaldehyde seawater for 30 minutes to 1 hour, once every 3 to 5 days.

③. Whirling disease (also called myxosporean disease) The diseased fish swim abnormally on the sea surface and cannot go down to the deep water layer. The pathogen is myxosporean cerebral worm. The prevention method is to bathe the fish with 0.34×10-6 potassium permanganate for 10 minutes when stocking the fish to keep the water fresh.

④. Fish with ringworm disease lose their luster, have poor appetite, and swim slowly. Some fish have ulcerated fins, increased mucus on the body and gills, local scales fall off, one or both eyeballs protrude, become inflamed, necrotic or fall off, lose balance when swimming, and spin around. The pathogen is ringworm. Soak in fresh water for 5 to 10 minutes, once a day, for 2 to 3 consecutive days, and the effect is good.

⑤. Trematode disease When the trematodes proliferate in large numbers, the fish may swim slowly, have more mucus on the gills, have congestion in some parts of the gills, and be anemic and light red in others. In severe cases, the fish may die from breathing difficulties. The pathogens are grouper diploid flukes, sex-dividing diploid flukes, grouper heterodividing diploid flukes, etc. The treatment methods can refer to dactylosis.

⑥. The symptoms of Cryptowhippiasis are similar to those of trematodiasis. The pathogen is Cryptowhippia, which can be killed by soaking in fresh water or 0.15×10-6 potassium permanganate solution for 5 minutes.

⑦. Gnat disease Gnat parasitizes on the surface and gills of fish, and absorbs nutrients from the fish with a sucker, causing damage to the integrity of the gill tissue, resulting in impaired respiratory function and eventually death of the diseased fish. Gnat reproduces and spreads quickly, especially in seasons with high seawater temperatures. There is currently no effective treatment method that does not pollute the environment, so attention should be paid to keeping the water clean during aquaculture production to effectively prevent the occurrence of this disease.

Parasites such as starch egg plus algae, trypanosomes, horn spores, and wheelworms are also harmful to grouper. In addition, nematode disease is a common parasitic disease of grouper, and the infection rate is very high. Especially under cage farming conditions, the infection of nematodes in feed fish to grouper is very serious. Sometimes dozens of nematodes appear in the body cavity, but because the symptoms are not obvious, they are not taken seriously.

2. Bacterial diseases

①. Tail rot disease: The tail surface is congested and inflamed, the skin is ulcerated, and the scales fall off. The edge of the fish lesion is congested and red, the center is swollen and ulcerated, and in severe cases, the muscles and bones are exposed, the fish loses balance, and dies in dozens of days. It often occurs from April to October, and the mortality rate is very high. For prevention, you can use a potassium permanganate bath with a concentration of 0.34×10-6 for 10 minutes, and antibiotics can also be used to relieve the condition.

②. The main symptoms of fish with ulcer disease are sluggish movement, swimming out of the water, ulcers on the fins and base, and even bruises all over the body. The ulcers vary in size and shape. The ulcers will deepen and eventually lead to death, with a high mortality rate. The pathogen is Vibrio vulnificus. The disease season is from April to November. Soaking in furazolidone for 3 to 5 minutes and taking antibiotics orally can control the disease. Formalin-inactivated vaccines from the vegetation of virulent strains of Vibrio vulnificus, heat-inactivated vaccines, and crude lipopolysaccharides extracted from Vibrio vulnificus can provide good immune protection for blue grouper and salmon grouper by intramuscular injection.

③. Bacterial white spot disease: Fingerprint-like red spots first appear on both sides of the fish body. In rare cases, they may occur on the head and tail, and the lesion site is slightly raised. As the disease progresses, the lesion turns into white spots, and the scales are slightly erected and easier to fall off. The white spots are clearer after the scales fall off. The fish lose their appetite, and the mortality rate is as high as 90%. It is prevalent in winter. The preventive measure is to avoid damage to the fish body. Antibiotics and anti-inflammatory drugs can alleviate the disease, but the effect is not obvious.

3. Other diseases

①. Nutritional disorder syndrome. The fish's swim bladder is inflated, the abdomen is swollen, and the fish loses balance, spinning on the water surface or the bottom of the cage, so it is commonly known as "bloating disease" or "spinning disease". Tissue sections show fatty degeneration, necrosis, vacuolation, and nuclear dissolution of the liver. The diseased fish's gills and internal organs show local or systemic inflammation, and the fish dies after floating on the water surface for several days, with a high mortality rate. During the epidemic season from May to October, the drug "Qingzhangning" is used for prevention and treatment, with good results.

②. Fish with hyperplastic kidney disease have varying degrees of abdominal distension, floating upside down or lying on their side, ulceration of fins and body surface, protruding eyeballs on one or both sides, blindness or lameness, and black or white body surface, which is the "bloating disease" that is seriously prevalent in grouper farming. The average white blood cell count is 48.09%, and the monocyte count is 2.82%, which is significantly higher than the normal value. The pathogen is a protozoan myxozoan with a high incidence rate. Feeding with the drug "Yubaosan" developed by the South China Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences has a significant effect.

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