Biological characteristics and breeding techniques of gentian grouper
2018-06-12 13:00:05
The scientific name of gentian grouper is Epinephelus Lanceolatus, which is the largest fish of the grouper, and belongs to the order Diptera, Taxus, Brancher, and Grouper. The main origin of gentian grouper is in Southeast Asia. Australian seas have also been found in China's South China Sea (Nansha Islands), but they are scarce. In recent years, its artificial breeding has been developing rapidly in Taiwan. China's southern coastal areas such as Guangdong and Fujian have also begun to introduce and develop artificial breeding of gentian grouper. At the same time, gentian grouper is also a popular object in the fishing industry.
First, biological characteristics
1. Morphological characteristics. The gentian grouper is long oval in shape, laterally flat, 2.7-fold to 3-fold longer than the body height, dorsal fin XI-15, arm fins III-7, pelvic fins I-5, pectoral fins 16, caudal fins 17, caudal fins For the garden. The posterior edge of the front humerus is serrated and the lower edge is smooth. The posterior edge of the humeral cap has 2 rough spines. The head of the head except the kiss end and the upper and lower jaws are finely scaled, the lateral line is completely parallel to the dorsal edge, and the dorsal fin spines and The fins are connected to each other without nicks. In addition to the pelvic fins, the fins are yellow and covered with small black dots. There are 5-7 horizontal stripes on the body side. The gentian grouper has a large split, a prominent jaw, and a retractable maxillary. The back of the maxilla expands and reaches below the posterior edge of the eye. The maxillary front has a number of canine teeth, followed by a cluster of inverted teeth. The sparsely small canine teeth have a villous tooth belt on the medial side. The mandibular front has a canine tooth opposite to the maxilla, followed by multiple lines of lashed teeth, and two rows of teeth on both sides are closely spaced.
2. Habitat habits: Gentian Grouper is a warm-water fish that is widely distributed in the Indian Ocean. In the tropical and subtropical waters of the Pacific and Atlantic Oceans, adults and juveniles will appear in estuarine brackish waters. The fish is a mid-lower layer of benthic fish, ferocious, strong regional, adult fish are not clustered, often inhabiting the coral reefs, rocky caves, sunken boats during the day, there is the habit of digging caves in the sea, night foraging. The sea area with smooth gravel sediments and seawater is a wide-salt coral reef fish that can survive in seawater with a salinity of 11-41 ,. The optimal salinity is 25-35 ‰ and the salinity is less than 5 ‰. Death, up to 15 minutes in fresh water. The suitable water temperature is 22°C-3O°C, but when the water temperature drops to 2O°C, appetite subsides, and when it falls below 15°C, it stops feeding and does not swim. Hi-light dark areas, in the cage when the hi-heavy bottom or concealed in the mesh wrinkles, body color with light and lighter, weaker and darker. The requirement for dissolved oxygen in seawater is not high. At a water temperature of 25°C, the oxygen consumption is 1.99 0• 53 μg/g.min, which is much less than the 4.650.81 μg/g.min.
3. Diet: The larvae, juveniles, and juveniles of gentian grouper feed on micro- and small-scale zooplankton and remain carnivorous after growing. Main food crustaceans (especially lobsters), sea urchins, and fish. Small turtles, even small sharks. The gentian grouper is a sneak attack animal and eats in a swallowing manner. It usually hides in the dark corners of the water or in coral reefs and other rocks. When a prey is found, it uses the sheltering effect of rocks and rocks to tighten the side of the eye. Staring at the prey and constantly adjusting its position and posture, it slowly approaches the prey and seeks to align its head and tail with the head and tail of the prey. It is curved in an S-shape. Once it enters the attack distance, it Suddenly attacking quickly, biting the prey, usually biting the head of the prey, then swallowing the prey, but sometimes biting the other parts of the prey, but also in the mouth to adjust until the prey is swallowed from the head, if the prey specifications Larger can not swallow, it may bite and give up prey.
4. Growth habits: The gentian grouper grows rapidly, raising the fry from about 6cm to 1kg, only 7 months to 8 months. After 1kg, the growth rate is faster and it can grow to 3kg-6kg in only two years. According to records, the wild caught individuals can weigh up to more than 280 kg. The gentian grouper is the best fish to make sashimi. The higher the market size is, the higher the price is. The general market size in Taiwan is 6-8kg.
5. Reproductive characteristics: The gentian grouper is a hermaphrodite hermaphrodite. In the development of the gonad, the ovary part develops first and becomes the female phase. Then, as the fish grows, some fish will undergo sexual transformation, and the female will become male. That is, when the gentian grouper is first matured (wild fish is 3rd age, Artificial breeding 2nd age) is female, the fish grows to a certain age (wild fish 4 inf - 5 years old, artificial breeding 3 inflrence) becomes male, so male broodstock is more difficult to obtain. In order to solve the problem of male broodstock deficiency in artificial reproduction, 17α-methyl-testosterone is implanted into the fish to induce early "sex change" of gentian grouper to obtain male broodstock with reproductive function. In the non-breeding season, it is difficult to judge males and females more than other grouper fish. During the breeding season, female females have enlarged abdomen and three holes. From the front to the back, they are the anus, gonopore and urinary foramen. The reproductive hole is dark red and slightly outward. There are many fine lines outward from the opening; males only have anal and urogenital holes. The gentian grouper is a spawning type, and its fecundity and broodstock age, size, and nutritional status. There is a close relationship between environmental factors and other conditions, and there is a large gap between them. Oviposition of each female is generally between 100,000 and 6.0 million grains. The fertilized eggs are spherical, transparent and colorless floating eggs. The general spawning behavior occurs from 6 o'clock in the evening to 2 o'clock in the morning. The males chase the female at the beginning, and then the two fish approach and swim side by side. Then the head and the front half jump out of the water for ovulation and ejaculation. In vitro fertilization is normal. In the case of continuous spawning for 3 days. The incubation time of fertilized eggs is greatly affected by temperature and salinity. Water temperature at 28°C-30°C requires approximately 20 hours of hatching. With increasing temperature, hatching time is shortened. However, water temperature is lower than 16°C or higher than 34°C, and embryonic development may be deformed or cause massive death. The suitable salinity for embryonic development is 25-3 3.5 ‰, the hatching rate of fertilized eggs below 15 ‰ salinity is O, the hatching rate of salinity 30 最佳 is the best, up to 9O%, the survival rate after three days 48%, and the survival rate was 65% on the first day after hatching at a salinity of 35 degrees, and all died within 25 days. In the artificial breeding, due to the small amount of male fish, male and female broodstock should be matched with a ratio of 1:1-3, and by injecting a certain dose of oxytocin, natural spawning can be made. The doses are human chorionic gonadotropin (HCG) 30O International Units - 500 International Units / kg body weight of fish and luteinizing hormone (LHRH-A) 25ug-50 ug / kg fish body weight, two kinds of mixed use, diluted with 0.6% physiological saline Suspensions were made and the injection volume was 1.5-2 mL. The back muscles were injected subcutaneously and the male fish was injected at a dose of one-third of the females. Artificial insemination should be dry insemination, oxytocin incubation, the water temperature is controlled at 25 °C ~ 28 °C, salinity 28-33 ‰, pH 7.8-8.5, shading on the pool, about 24 hours hatched.
Second, seed cultivation:
1. Seedling pond: The area is 25-3O square meters, the pool depth is 1.5-1.8m, there must be sufficient diffuse light above the nursery pond to avoid direct sunlight, and every 2 square meters of cloth in the pool is oxygenated with aerogel to keep the dissolved oxygen at 5mg. /L.
2. Fish fry stocking: Before stocking, the ponds are kept at a depth of 70-80cm, and 3O-500,000/mL micro-green algae fluid is added, and the newly hatched larvae are moved from the hatching cage into the pond at a stocking density of 20,000/sq. About meters, if the fertilized eggs hatch directly in the nursery pond, the egg density is 2.5-3 million grains/cubic meter.
3. Feeding management: After hatching, the fish body is slender and has no swimming ability. The temperature of the water was 25 hours after hatching at 25°C and 29°C. The yolk sac was absorbed after 72 hours. At this time, food intake began. Most of the fry are gathered in the upper layer of the fish pond and like to feed along the pool wall. With the development of the fry, it is necessary to change the feeding of different food organisms. According to the conversion of the bait during the development from the yolk sac to the juvenile, it can be divided into three cultivation stages:
The first stage is the yolk sac larvae to the larvae: the fry is converted from endogenous nutrition to exogenous nutrition, usually 2 to 3 days after opening the food. The exogenous nutrients fed at this time were small zooplankton, mainly oyster fertilized eggs and larval prototype rotifers. At the same time, a small amount of green algae water was added, and then about 10 ppm of photosynthetic bacteria could be fed.
The second stage is from the late larvae to the juvenile stage: usually after the first stage until the 20th. At this time the fry has an elongated dorsal fin spine and a pelvic spine at the left and right, shaped like a kite, commonly known as the winged antelope. Feeding from small zooplankton to large zooplankton, the main food has rotifers. After feeding for about 5 days to 7 days, the dorsal fin and left and right pelvic fins of the fry begin to grow long spines, and the dorsal fin and left and right pelvic fins are extended with time, similar in shape. flying fish. At this time, water quality control is very important. Try to keep the water quality as stable as possible. It is better to keep the water color green. At the end of this phase, small copepods, Artemia larvae, etc. can be fed, and the pelvic fin spines are retracted on the 15th and the long spines of the dorsal spines are retracted on the 2Oth.
The third stage is the late juvenile to juvenile period: the fry has grown to 5cm-6cm. Due to the growth of other fin spines, the long spines of the former dorsal fin and the left and right pelvic fins “disappearâ€. This means that the fry is about to metamorphose into the juvenile period of benthic life and feed to benthic bait. The main food organisms are Artemia, copepods, prawn, fish, shrimp, and shellfish.
In the breeding process of seedlings, in order to improve the survival rate, the following points should be noted:
(1) Timely screening of sub-pools. The gentian grouper may experience residual food in larvae longer than 7mm in length. Sometimes, due to the large number of individuals that are swallowed, swallowing does not enter or exit, often resulting in loss of both ends, thus greatly reducing the survival rate of seedlings. In order to avoid the occurrence of residual food, it is usually screened once in about 2 weeks. When the water temperature is low, it can be filtered once in 20 days to 30 days.
(2) According to different stages, timely change. Feed; timely feed a sufficient amount of palatability food, increase the frequency of feeding, 4 times -5 times a day. The food organisms such as rotifers and Artemia were applied before the feeding of yeast (the rotifers fed yeast were supplemented with green algae for 12 hours) and highly unsaturated fatty acids (EPA and DHA) were used for intensive cultivation.
(3) Maintain a reasonable cultivation density. For a full-length 10mm larvae, the density should be less than 10,000/m3, and when the total length exceeds 10mm, the density should be maintained at 500 to 1000/m3.
(4) Set up shelters in the water body, such as hanging algae or putting plastic pipes at the bottom, which can reduce mutual food.
Third, adult fish breeding:
1. Site selection and pond preparation: Culture of gentian grouper mainly includes cage culture and pond culture. In cage culture, the sheltered sea area should be provided with good shelter conditions and little wind and waves. Sandy bottom, reef bottom, and gravel bottom are preferred. The water depth at low tide should be 4m or more. The flow rate is moderate, and the flow rate in the cage remains at 0. 1~O. 2m/s is good, winter water temperature is not lower than 15°C, salinity is 25-32‰. pH 7-9. There is no large amount of fresh water injected during heavy rain, the salinity is not less than 16 ‰, and the transparency is more than 1.5m. Pond culture can use shrimp ponds for transformation. Pond water depth should be maintained at 2m-3m, and the area is between 5 and 10 acres. Artificial reefs can be installed at the bottom of the pool; before soaking, bleached lime with 75kg or 10-15ppm lime per acre is soaked for 2 days. After 3 days, drain, expel 2-10 days, then inject 10-20cm of fresh water, use 4-10kg of tea acre per acre to remove the wild fish in the pond, etc., and fill the pond with water after 5-7 days of drug treatment. Higher transparency can be introduced into green algae water and fertilization.
2. Breeding management: When the fry is cultivated to a size of 5cm-8cm, it can be placed in cages or raised in ponds. In order to prevent fish fry death due to excessive changes in water temperature, it is advisable to stock fry in the early morning or evening when the weather is fine, and to do temperature adjustment work. Because of the fast growth rate of gentian grouper, the stocking density should not be too high, and stocking of 30 to 5 O0 per acre is recommended. The cage stocking density can be controlled from 15 to 30/m3. In practice, we have found that the maximum size of the gentian grouper consuming fish is equivalent to 52%-55% of its total length. Therefore, during the breeding period, if the size of the gentian grouper differs by 1/3 In the above, timely screening should be conducted for grading so as to avoid mutual food. Cage fishes can be mixed in cages, and their appetite is used to stimulate the appetite of gentian groupers. At the same time, blue-fishes are mixed to remove cage attachments and residual baits. In areas with low winter temperatures, winter preparations should be made. Net cages can be used for deep winter caisson wintering.
3. Feeding Technology: The gentian grouper is a carnivorous fish. When it is hungry, there is no strict selectivity for food. As long as it is animal food, it feeds regardless of life or death. In nature, it mainly eats coelenterates, crustaceans, and mollusks. Fish and so on. Artificial fish can be used to feed small, fresh fish that are good in freshness, crushed into pulp, and mixed with squid feed for feeding. In the land-based fish ponds, artificial fish reefs can be used to feed the feed to the artificial reefs at fixed spots to bait. If compound feed is used, the degree of softness and hardness of gentian grouper will be determined. The palatability such as color and taste is more demanding, and soft particles (softness of about 30% of water content) should be selected, and light-colored floating feed should be used. Feed particles are too hard to have spit food phenomenon, too soft do not like to eat; feed particle size is generally 1/3-1/4 gentian grouper diameter, shape is a long strip, length and width of 2-3:1 Too small feed does not like to eat. The number of feedings is twice a day, and the water temperature in winter is less than 2O°C and can be taken once a day or once every two days. Each dose was 3% to 5% of the body weight of the fish, depending on the state of food intake, and the degree of appetite decreased. When feeding, they should be sprinkled slowly and in batches. After grabbing the feed before the end of the batch, sprinkle the next batch until the feed is full, and never dump the feed into the cage or pool at one time. The gentian grouper Do not eat food at the bottom.
4. Disease prevention and control: The gentian grouper is particularly greedy. The common fish diseases in feeding are due to excessive feeding, resulting in gastro-intestinal disease. The stomach is prone to flatulence and forms “dilatationâ€. Therefore, feeding should be done well; Regularly add allicin for oral prevention; if "expansion" occurs, needles can be used to eliminate gas. In the breeding of gentian grouper, the main attention should be paid to the prevention of parasites such as trichomonads and bell-shaped worms, and special attention should be paid to disinfection of the water environment.
First, biological characteristics
1. Morphological characteristics. The gentian grouper is long oval in shape, laterally flat, 2.7-fold to 3-fold longer than the body height, dorsal fin XI-15, arm fins III-7, pelvic fins I-5, pectoral fins 16, caudal fins 17, caudal fins For the garden. The posterior edge of the front humerus is serrated and the lower edge is smooth. The posterior edge of the humeral cap has 2 rough spines. The head of the head except the kiss end and the upper and lower jaws are finely scaled, the lateral line is completely parallel to the dorsal edge, and the dorsal fin spines and The fins are connected to each other without nicks. In addition to the pelvic fins, the fins are yellow and covered with small black dots. There are 5-7 horizontal stripes on the body side. The gentian grouper has a large split, a prominent jaw, and a retractable maxillary. The back of the maxilla expands and reaches below the posterior edge of the eye. The maxillary front has a number of canine teeth, followed by a cluster of inverted teeth. The sparsely small canine teeth have a villous tooth belt on the medial side. The mandibular front has a canine tooth opposite to the maxilla, followed by multiple lines of lashed teeth, and two rows of teeth on both sides are closely spaced.
2. Habitat habits: Gentian Grouper is a warm-water fish that is widely distributed in the Indian Ocean. In the tropical and subtropical waters of the Pacific and Atlantic Oceans, adults and juveniles will appear in estuarine brackish waters. The fish is a mid-lower layer of benthic fish, ferocious, strong regional, adult fish are not clustered, often inhabiting the coral reefs, rocky caves, sunken boats during the day, there is the habit of digging caves in the sea, night foraging. The sea area with smooth gravel sediments and seawater is a wide-salt coral reef fish that can survive in seawater with a salinity of 11-41 ,. The optimal salinity is 25-35 ‰ and the salinity is less than 5 ‰. Death, up to 15 minutes in fresh water. The suitable water temperature is 22°C-3O°C, but when the water temperature drops to 2O°C, appetite subsides, and when it falls below 15°C, it stops feeding and does not swim. Hi-light dark areas, in the cage when the hi-heavy bottom or concealed in the mesh wrinkles, body color with light and lighter, weaker and darker. The requirement for dissolved oxygen in seawater is not high. At a water temperature of 25°C, the oxygen consumption is 1.99 0• 53 μg/g.min, which is much less than the 4.650.81 μg/g.min.
3. Diet: The larvae, juveniles, and juveniles of gentian grouper feed on micro- and small-scale zooplankton and remain carnivorous after growing. Main food crustaceans (especially lobsters), sea urchins, and fish. Small turtles, even small sharks. The gentian grouper is a sneak attack animal and eats in a swallowing manner. It usually hides in the dark corners of the water or in coral reefs and other rocks. When a prey is found, it uses the sheltering effect of rocks and rocks to tighten the side of the eye. Staring at the prey and constantly adjusting its position and posture, it slowly approaches the prey and seeks to align its head and tail with the head and tail of the prey. It is curved in an S-shape. Once it enters the attack distance, it Suddenly attacking quickly, biting the prey, usually biting the head of the prey, then swallowing the prey, but sometimes biting the other parts of the prey, but also in the mouth to adjust until the prey is swallowed from the head, if the prey specifications Larger can not swallow, it may bite and give up prey.
4. Growth habits: The gentian grouper grows rapidly, raising the fry from about 6cm to 1kg, only 7 months to 8 months. After 1kg, the growth rate is faster and it can grow to 3kg-6kg in only two years. According to records, the wild caught individuals can weigh up to more than 280 kg. The gentian grouper is the best fish to make sashimi. The higher the market size is, the higher the price is. The general market size in Taiwan is 6-8kg.
5. Reproductive characteristics: The gentian grouper is a hermaphrodite hermaphrodite. In the development of the gonad, the ovary part develops first and becomes the female phase. Then, as the fish grows, some fish will undergo sexual transformation, and the female will become male. That is, when the gentian grouper is first matured (wild fish is 3rd age, Artificial breeding 2nd age) is female, the fish grows to a certain age (wild fish 4 inf - 5 years old, artificial breeding 3 inflrence) becomes male, so male broodstock is more difficult to obtain. In order to solve the problem of male broodstock deficiency in artificial reproduction, 17α-methyl-testosterone is implanted into the fish to induce early "sex change" of gentian grouper to obtain male broodstock with reproductive function. In the non-breeding season, it is difficult to judge males and females more than other grouper fish. During the breeding season, female females have enlarged abdomen and three holes. From the front to the back, they are the anus, gonopore and urinary foramen. The reproductive hole is dark red and slightly outward. There are many fine lines outward from the opening; males only have anal and urogenital holes. The gentian grouper is a spawning type, and its fecundity and broodstock age, size, and nutritional status. There is a close relationship between environmental factors and other conditions, and there is a large gap between them. Oviposition of each female is generally between 100,000 and 6.0 million grains. The fertilized eggs are spherical, transparent and colorless floating eggs. The general spawning behavior occurs from 6 o'clock in the evening to 2 o'clock in the morning. The males chase the female at the beginning, and then the two fish approach and swim side by side. Then the head and the front half jump out of the water for ovulation and ejaculation. In vitro fertilization is normal. In the case of continuous spawning for 3 days. The incubation time of fertilized eggs is greatly affected by temperature and salinity. Water temperature at 28°C-30°C requires approximately 20 hours of hatching. With increasing temperature, hatching time is shortened. However, water temperature is lower than 16°C or higher than 34°C, and embryonic development may be deformed or cause massive death. The suitable salinity for embryonic development is 25-3 3.5 ‰, the hatching rate of fertilized eggs below 15 ‰ salinity is O, the hatching rate of salinity 30 最佳 is the best, up to 9O%, the survival rate after three days 48%, and the survival rate was 65% on the first day after hatching at a salinity of 35 degrees, and all died within 25 days. In the artificial breeding, due to the small amount of male fish, male and female broodstock should be matched with a ratio of 1:1-3, and by injecting a certain dose of oxytocin, natural spawning can be made. The doses are human chorionic gonadotropin (HCG) 30O International Units - 500 International Units / kg body weight of fish and luteinizing hormone (LHRH-A) 25ug-50 ug / kg fish body weight, two kinds of mixed use, diluted with 0.6% physiological saline Suspensions were made and the injection volume was 1.5-2 mL. The back muscles were injected subcutaneously and the male fish was injected at a dose of one-third of the females. Artificial insemination should be dry insemination, oxytocin incubation, the water temperature is controlled at 25 °C ~ 28 °C, salinity 28-33 ‰, pH 7.8-8.5, shading on the pool, about 24 hours hatched.
Second, seed cultivation:
1. Seedling pond: The area is 25-3O square meters, the pool depth is 1.5-1.8m, there must be sufficient diffuse light above the nursery pond to avoid direct sunlight, and every 2 square meters of cloth in the pool is oxygenated with aerogel to keep the dissolved oxygen at 5mg. /L.
2. Fish fry stocking: Before stocking, the ponds are kept at a depth of 70-80cm, and 3O-500,000/mL micro-green algae fluid is added, and the newly hatched larvae are moved from the hatching cage into the pond at a stocking density of 20,000/sq. About meters, if the fertilized eggs hatch directly in the nursery pond, the egg density is 2.5-3 million grains/cubic meter.
3. Feeding management: After hatching, the fish body is slender and has no swimming ability. The temperature of the water was 25 hours after hatching at 25°C and 29°C. The yolk sac was absorbed after 72 hours. At this time, food intake began. Most of the fry are gathered in the upper layer of the fish pond and like to feed along the pool wall. With the development of the fry, it is necessary to change the feeding of different food organisms. According to the conversion of the bait during the development from the yolk sac to the juvenile, it can be divided into three cultivation stages:
The first stage is the yolk sac larvae to the larvae: the fry is converted from endogenous nutrition to exogenous nutrition, usually 2 to 3 days after opening the food. The exogenous nutrients fed at this time were small zooplankton, mainly oyster fertilized eggs and larval prototype rotifers. At the same time, a small amount of green algae water was added, and then about 10 ppm of photosynthetic bacteria could be fed.
The second stage is from the late larvae to the juvenile stage: usually after the first stage until the 20th. At this time the fry has an elongated dorsal fin spine and a pelvic spine at the left and right, shaped like a kite, commonly known as the winged antelope. Feeding from small zooplankton to large zooplankton, the main food has rotifers. After feeding for about 5 days to 7 days, the dorsal fin and left and right pelvic fins of the fry begin to grow long spines, and the dorsal fin and left and right pelvic fins are extended with time, similar in shape. flying fish. At this time, water quality control is very important. Try to keep the water quality as stable as possible. It is better to keep the water color green. At the end of this phase, small copepods, Artemia larvae, etc. can be fed, and the pelvic fin spines are retracted on the 15th and the long spines of the dorsal spines are retracted on the 2Oth.
The third stage is the late juvenile to juvenile period: the fry has grown to 5cm-6cm. Due to the growth of other fin spines, the long spines of the former dorsal fin and the left and right pelvic fins “disappearâ€. This means that the fry is about to metamorphose into the juvenile period of benthic life and feed to benthic bait. The main food organisms are Artemia, copepods, prawn, fish, shrimp, and shellfish.
In the breeding process of seedlings, in order to improve the survival rate, the following points should be noted:
(1) Timely screening of sub-pools. The gentian grouper may experience residual food in larvae longer than 7mm in length. Sometimes, due to the large number of individuals that are swallowed, swallowing does not enter or exit, often resulting in loss of both ends, thus greatly reducing the survival rate of seedlings. In order to avoid the occurrence of residual food, it is usually screened once in about 2 weeks. When the water temperature is low, it can be filtered once in 20 days to 30 days.
(2) According to different stages, timely change. Feed; timely feed a sufficient amount of palatability food, increase the frequency of feeding, 4 times -5 times a day. The food organisms such as rotifers and Artemia were applied before the feeding of yeast (the rotifers fed yeast were supplemented with green algae for 12 hours) and highly unsaturated fatty acids (EPA and DHA) were used for intensive cultivation.
(3) Maintain a reasonable cultivation density. For a full-length 10mm larvae, the density should be less than 10,000/m3, and when the total length exceeds 10mm, the density should be maintained at 500 to 1000/m3.
(4) Set up shelters in the water body, such as hanging algae or putting plastic pipes at the bottom, which can reduce mutual food.
Third, adult fish breeding:
1. Site selection and pond preparation: Culture of gentian grouper mainly includes cage culture and pond culture. In cage culture, the sheltered sea area should be provided with good shelter conditions and little wind and waves. Sandy bottom, reef bottom, and gravel bottom are preferred. The water depth at low tide should be 4m or more. The flow rate is moderate, and the flow rate in the cage remains at 0. 1~O. 2m/s is good, winter water temperature is not lower than 15°C, salinity is 25-32‰. pH 7-9. There is no large amount of fresh water injected during heavy rain, the salinity is not less than 16 ‰, and the transparency is more than 1.5m. Pond culture can use shrimp ponds for transformation. Pond water depth should be maintained at 2m-3m, and the area is between 5 and 10 acres. Artificial reefs can be installed at the bottom of the pool; before soaking, bleached lime with 75kg or 10-15ppm lime per acre is soaked for 2 days. After 3 days, drain, expel 2-10 days, then inject 10-20cm of fresh water, use 4-10kg of tea acre per acre to remove the wild fish in the pond, etc., and fill the pond with water after 5-7 days of drug treatment. Higher transparency can be introduced into green algae water and fertilization.
2. Breeding management: When the fry is cultivated to a size of 5cm-8cm, it can be placed in cages or raised in ponds. In order to prevent fish fry death due to excessive changes in water temperature, it is advisable to stock fry in the early morning or evening when the weather is fine, and to do temperature adjustment work. Because of the fast growth rate of gentian grouper, the stocking density should not be too high, and stocking of 30 to 5 O0 per acre is recommended. The cage stocking density can be controlled from 15 to 30/m3. In practice, we have found that the maximum size of the gentian grouper consuming fish is equivalent to 52%-55% of its total length. Therefore, during the breeding period, if the size of the gentian grouper differs by 1/3 In the above, timely screening should be conducted for grading so as to avoid mutual food. Cage fishes can be mixed in cages, and their appetite is used to stimulate the appetite of gentian groupers. At the same time, blue-fishes are mixed to remove cage attachments and residual baits. In areas with low winter temperatures, winter preparations should be made. Net cages can be used for deep winter caisson wintering.
3. Feeding Technology: The gentian grouper is a carnivorous fish. When it is hungry, there is no strict selectivity for food. As long as it is animal food, it feeds regardless of life or death. In nature, it mainly eats coelenterates, crustaceans, and mollusks. Fish and so on. Artificial fish can be used to feed small, fresh fish that are good in freshness, crushed into pulp, and mixed with squid feed for feeding. In the land-based fish ponds, artificial fish reefs can be used to feed the feed to the artificial reefs at fixed spots to bait. If compound feed is used, the degree of softness and hardness of gentian grouper will be determined. The palatability such as color and taste is more demanding, and soft particles (softness of about 30% of water content) should be selected, and light-colored floating feed should be used. Feed particles are too hard to have spit food phenomenon, too soft do not like to eat; feed particle size is generally 1/3-1/4 gentian grouper diameter, shape is a long strip, length and width of 2-3:1 Too small feed does not like to eat. The number of feedings is twice a day, and the water temperature in winter is less than 2O°C and can be taken once a day or once every two days. Each dose was 3% to 5% of the body weight of the fish, depending on the state of food intake, and the degree of appetite decreased. When feeding, they should be sprinkled slowly and in batches. After grabbing the feed before the end of the batch, sprinkle the next batch until the feed is full, and never dump the feed into the cage or pool at one time. The gentian grouper Do not eat food at the bottom.
4. Disease prevention and control: The gentian grouper is particularly greedy. The common fish diseases in feeding are due to excessive feeding, resulting in gastro-intestinal disease. The stomach is prone to flatulence and forms “dilatationâ€. Therefore, feeding should be done well; Regularly add allicin for oral prevention; if "expansion" occurs, needles can be used to eliminate gas. In the breeding of gentian grouper, the main attention should be paid to the prevention of parasites such as trichomonads and bell-shaped worms, and special attention should be paid to disinfection of the water environment.
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