Freshwater sharks, also known as pangasias sutchi, and pudding fish, commonly known as tiger sharks, are part of the oyster-shaped head, the nymphalidae, and the fish genus, which are mainly distributed in the southeast Asia and are native to Malaysia and Thailand. In other places, China began to introduce it in 1998. Freshwater shark breeding technology is simple, feed requirements are not high, meat quality (no intermuscular puncture) is delicate and delicious, and economic benefits are significant (commercial fish market value is 60-80 yuan/kg). Besides freshwater sharks, they can be used as food fish. Chondroitin sulfate, which has higher ornamental value and its cartilage tissue contains higher nutritional value and medicinal value, is a better freshwater culture species in China. At present, freshwater sharks have set off a breeding boom in southern China and will continue to show good market prospects in the coming years. This article describes the biological characteristics of freshwater sharks and artificial breeding techniques for reference.
Biological characteristics
1.1 Morphological characteristics Freshwater sharks are smooth and scaleless. They are divided into black, white and gray body types. They are long flat on one side, uplift on the back, conical head flat, short kiss, lower subaortic, distant nostrils, and aponeurosis. Not connected to the cheeks. With fat fins, must be 2 pairs, whiskers, whiskers and a pair of sideways straight. There are 3-4 longitudinal blue stripes on the juvenile side, and adult fish stripes disappear. Large, with the function of assisting the breathing of air, is not easy to lack of oxygen, and when the carp species in the same pool polyculture raises their oxygen deficiency, they can still survive.
1.2 Habits of life Freshwater sharks are tropical fish. They are benthic habitats. The suitable living temperature is 20 to 30°C, preferably 24 to 28°C. The appropriate pH value is 6 to 7.2. The water temperature starts to die when the water temperature falls below 12°C. The food intake and activity decreased significantly when it fell below 18°C. It could not naturally overwinter in the northern regions of China, and it was suitable for breeding in the south or greenhouses and indoor breeding. The growth rate was fast, generally about 1 kg in 1 year. Freshwater sharks are more adaptable to the environment, can tolerate hypoxia and swim quickly, but have a timid nature and are constantly excited in the water when disturbed by the outside world. The breeding environment should be quiet.
1.3 Edible freshwater sharks have omnivorous feeding habits mainly based on herbivorous feeding. Juveniles feed on plankton, such as rotifers, copepods, horny horns, or various algae, and may also feed artificial compound feed. Aquatic plants and artificial feeds are used for food, but also eat leftovers, rice bran, wheat bran, and residual feed. If there is no specialized artificial feed, tilapia feed can be used instead, and pig manure, chicken manure, duck dung can also be fed.
1.4 Breeding habits Freshwater sharks tend to mature later, generally requiring 3 to 4 instars and weighing more than 3 kg to reproduce. Every year from June to September is the breeding season. Is a spawning fish 1 year, each spawn about 300,000 to 700,000 tablets, eggs, small, sticky, yellow-green, transparent.
2. Seed cultivation
2.1 Fry cultivation The cultivation pool is generally a cement pool with a depth of 1.0-1.5m. It is convenient for drainage and irrigation, and a grille is installed at the inlet and outlet to prevent enemy organisms from entering the pool. The fry were disinfected with clear lime and other drugs in front of the pool to kill pathogenic bacteria and harmful organisms. The amount of quicklime is 150kg/667m2. Add basal fertilizer 1-2d after disinfection and add water to facilitate the growth of bait organisms.
About 1 d after hatching, the fry can reach 1.0 cm in length and has been able to feed on copepods and branches. At this point, the fry pool cultivation was started. Before soaking, soaking with 3 to 4% salt water for about 5 minutes. Before stocking, apply several fry to test the water. The initial pool water depth starts from 0.6m, and is gradually deepened with microfluidic water; the stocking density is 50-100/m2, and special attention should be paid to the temperature difference not exceeding 3°C during stocking.
The second day after the seedlings were placed, they were fed with cooked egg yolks, which were divided into 6 times every 4 hours. After 7 days, the fish meal was changed. Since the fish meal is likely to cause froth bubble disease, it should be fed several times. During the cultivation process, it is best to drain 10 cm of sewage every day from the bottom of the pool, and add new water. Every 10 days, 1 ppm of bleach is used to prevent disease.
After about 30 days of cultivation, the fry generally grows to a size of about 4 to 5 cm in length, and can be placed in large pools for fingerling cultivation.
2.2. Breeding of fingerlings Individual stocks with strong physique, no disease, no injuries, neat specifications, and strong water-returning qualities should be selected. The area of ​​fish breeding ponds is preferably 500-2000 m2, with a water depth of 1.5-2.0 m. After the fish species have been stocked for 7-10 d, they shall be sterilized with quick lime ponds and then used as spares. When stocking, attention should be paid to the temperature difference should not be too large, the weather is clear, when the wind is smaller, the seedlings have better results. Fish seedlings were soaked with 3 to 4% salt water for about 5 minutes. Ponds with stocking densities of 3 to 4 tails/m2, fish ponds with adequate water sources, good water quality, and large water exchange volume can be appropriately increased in stocking density to reach 5-6 tails/m2.
Fish species are best fed with full-grain pellets containing more than 35% crude protein. The fish species began to feed on the third day after the pond, the initial reasons for transportation scared, etc., eating less, it is appropriate to take a small number of multiple feeding, 5 ~ 7d, with the fish species into the normal food, feeding time To reduce it appropriately, every day, every time in the afternoon, the amount of fish fed every day should be about 3% to 5% of the weight of the fish body, and it should be appropriately increased or decreased according to the specific situation. After 10 days, the fish body will be as long as 5~6cm. The principle of feeding is that 80% of the fry are fed and leave.
3. Adult fish farming At present, the artificial breeding of freshwater sharks is mainly based on pond culture, and cage culture is available where conditions permit.
3.1 Pond culture Aquaculture waters should be of suitable area, convenient for drainage and drainage, adequate water supply, and the water quality should meet the fishery water standard, with a water depth of 1.0-2.0m. The ponds should be sterilized in clear ponds in the week prior to planting. Fertilizer water quality, water quality fertilizer, and appropriate water temperature are favorable to the rapid growth of freshwater sharks. Fertilizer after fry under the aquaculture, stocking density for the fry stage put 6 ~ 8 / m3, fish stage put 3 ~ 4 / m3, adult fish rearing 2 ~ 3 tail / m3.
3.1.1 Single ponds 1000 to 3000 m2 can be water depth of 1 ~ 2m, every year from April to May, when the water temperature is above 18 °C, stocking specifications of 5 ~ 10cm seedlings, put 1000 ~ 3000 tails per 667 m2. Use artificial feed or small fish, shrimp, rice bran, etc. to feed.
If feeding artificial compound feed requires tame food, generally it is better to tame food during the period of the flattened piece. That is, when the fish is baited after the fish is stocked, the objects (such as pots, buckets, etc.) may be struck or audible, so that the fish form a conditional reflex. Focus on bait stations to catch food. Normally, it is fed twice a day, about 40% of the diet is fed at about 8 to 9 am, and about 60% of the diet is fed at about 3 to 4 in the afternoon. At the same time, the bait should be flexibly adjusted according to the principles of “four rules†(timing, qualitative, quantitative, and positioning) and “three observations†(see the weather, water quality, and eating habits of fish), and neither waste nor fish. Saturation to ensure that there is sufficient nutrition for the growth of fish.
3.1.2 Polyculture can be mixed with common home fish, tilapia, shrimp, crab, etc. Generally, 60 to 100 tails per 667 m2, 5 to 10 cm in size, without additional feeding, can make full use of pond water space, Improve production and efficiency.
3.2 Cage Aquaculture cages with a volume of 15 to 20 m3 and 50 to 150 tails/m3 of 8 to 10 cm in length are released. In general, 60 to 100 kg of fish can be produced per m3. Must be fed with artificial feed, protein requirements in more than 35%. Generally, the survival rate of aquaculture reaches 80% to 90%, which is lower than the survival rate of pond culture. This is related to the benthic life of freshwater sharks.
Seedling stage can be poured daily soy milk, powdered feed, etc., cast 3 to 4 times a day, after a week can be used to feed red worms, leeches, or artificial pellet feed. When feeding, we still need to do "three look" and "four sets." To be able to eat without being wasted, but the fish is bulimia, and should avoid over-eating, generally every time 80% of fish in the cages eat 80% full, quality and quantity, so that the fish grow faster. In the breeding process, cages are still required to be cleaned frequently to ensure good water exchange, and to prevent escape, theft, disease prevention, and flood control.
4. Disease prevention and treatment Freshwater sharks have strong disease resistance. As long as they are well-prevented and have fewer diseases, their diseases mainly include the following:
4.1 Enteritis disease fish Slow action, do not eat, abdomen enlargement, body color black, anal swelling, light pressure on the abdomen by hand, there is yellow mucus outflow, open abdominal cavity, increased body fluid, intestinal wall congestion, reddish-brown, fasting Black mucus, sick fish died faster, control can use "Allicin", add 0.1 ~ 0.3g per kg of feed fed; can also be used "Fu Ling Ling" 0.2 ~ 0.3g/kg feed added; "Cerberine hydrochloride "Feeding is the most effective. Water body is disinfected every other day with "dichlorohydantoin" or "bromochloroheine".
4.2 white spot disease, also known as small melon worm. On the fish's skin, fins or gills, there are white spots, and a large amount of mucus is secreted. Microscopic examination reveals the small melon body. The medicines used can be used to kill 200g of fish per 667m21m water depth, such as "fish and insect killing"; "insecticide" 0.5mg/l splash; or use "fish and insect clear" 4% added feed to drive insects, The use of fish and insecticides, insecticides, or trichlorfon should be used with caution. The fish is more sensitive to them, and the side effects of the above-mentioned Chinese medicine preparations are less.
4.3 Bubble Disease Freshwater sharks are prone to air bubbles when applying fertilizers such as agricultural organic fertilizers. Under oxygen saturation, seedlings are prone to cause bubble disease. Excessive ammonia-nitrogen gas at the bottom of the pool can also cause air bubbles and cause death. Therefore, fertilizers should be used in water bodies such as "Fei Shui Bao" or nitrogen fertilizer, phosphate fertilizer, and potassium fertilizer mixture. The bottom of the pool should be treated with "bottom net", "ammonia net", etc. In case of lack of oxygen, appropriate amount of oxygenating agent should be used, and less or no oxygen pump should be used. And pay attention to keeping the water fresh and lively, which can effectively prevent the occurrence of the disease.
In addition, trichomonads, third-generation worms, ringworms, etc. may have parasitic fish. Its treatment is similar to white spot disease. A variety of vitamins should be added to the feed, and drugs such as “Allicin†or “Fodamine†and “Fish Health†should be added to prevent the occurrence of fish diseases such as enteritis, skin decay, and acne. Water, such as "Bromochlorohydantoin" and "Chlorine Dioxide", are regularly sprayed on water to prevent bacterial or viral diseases. In the prevention of drugs should be avoided as much as possible the use of side effects of chemicals, such as potassium permanganate, formaldehyde, copper sulfate, malachite green, mercury nitrate and so on. Because freshwater sharks do not have Scales, they are more sensitive to chemical drugs and should use more Chinese herbal medicines for prevention and treatment. However, they should pay attention to the incompatibility of Chinese herbal medicines when they are used. Also note that the concentration of the drug should be slightly lower than that of the ichthyotic fish.
5. Breeding prospects Freshwater sharks have shown great market potential since they were introduced into China. However, they are still breeding in southern provinces and cities such as Guangdong and Hainan, and Hubei, Jiangsu, Sichuan, Chongqing, Zhejiang and other provinces and cities have also cultivated. However, the scale of breeding needs to be improved. Due to the inability of the fish to naturally overwinter in the northern regions of China, swimming in some areas is dominated by only part of the season. The reason for the higher price of the fish is mainly because the seed of the fish is basically imported. How to increase its breeding effect in China will be the main subject of future research on fishery scientists. However, considering the breeding technology, economic benefits, and nutritional value, freshwater white sharks will continue to be active in the aquatic product market in the next few years and will be accepted by more and more consumers.
Biological characteristics
1.1 Morphological characteristics Freshwater sharks are smooth and scaleless. They are divided into black, white and gray body types. They are long flat on one side, uplift on the back, conical head flat, short kiss, lower subaortic, distant nostrils, and aponeurosis. Not connected to the cheeks. With fat fins, must be 2 pairs, whiskers, whiskers and a pair of sideways straight. There are 3-4 longitudinal blue stripes on the juvenile side, and adult fish stripes disappear. Large, with the function of assisting the breathing of air, is not easy to lack of oxygen, and when the carp species in the same pool polyculture raises their oxygen deficiency, they can still survive.
1.2 Habits of life Freshwater sharks are tropical fish. They are benthic habitats. The suitable living temperature is 20 to 30°C, preferably 24 to 28°C. The appropriate pH value is 6 to 7.2. The water temperature starts to die when the water temperature falls below 12°C. The food intake and activity decreased significantly when it fell below 18°C. It could not naturally overwinter in the northern regions of China, and it was suitable for breeding in the south or greenhouses and indoor breeding. The growth rate was fast, generally about 1 kg in 1 year. Freshwater sharks are more adaptable to the environment, can tolerate hypoxia and swim quickly, but have a timid nature and are constantly excited in the water when disturbed by the outside world. The breeding environment should be quiet.
1.3 Edible freshwater sharks have omnivorous feeding habits mainly based on herbivorous feeding. Juveniles feed on plankton, such as rotifers, copepods, horny horns, or various algae, and may also feed artificial compound feed. Aquatic plants and artificial feeds are used for food, but also eat leftovers, rice bran, wheat bran, and residual feed. If there is no specialized artificial feed, tilapia feed can be used instead, and pig manure, chicken manure, duck dung can also be fed.
1.4 Breeding habits Freshwater sharks tend to mature later, generally requiring 3 to 4 instars and weighing more than 3 kg to reproduce. Every year from June to September is the breeding season. Is a spawning fish 1 year, each spawn about 300,000 to 700,000 tablets, eggs, small, sticky, yellow-green, transparent.
2. Seed cultivation
2.1 Fry cultivation The cultivation pool is generally a cement pool with a depth of 1.0-1.5m. It is convenient for drainage and irrigation, and a grille is installed at the inlet and outlet to prevent enemy organisms from entering the pool. The fry were disinfected with clear lime and other drugs in front of the pool to kill pathogenic bacteria and harmful organisms. The amount of quicklime is 150kg/667m2. Add basal fertilizer 1-2d after disinfection and add water to facilitate the growth of bait organisms.
About 1 d after hatching, the fry can reach 1.0 cm in length and has been able to feed on copepods and branches. At this point, the fry pool cultivation was started. Before soaking, soaking with 3 to 4% salt water for about 5 minutes. Before stocking, apply several fry to test the water. The initial pool water depth starts from 0.6m, and is gradually deepened with microfluidic water; the stocking density is 50-100/m2, and special attention should be paid to the temperature difference not exceeding 3°C during stocking.
The second day after the seedlings were placed, they were fed with cooked egg yolks, which were divided into 6 times every 4 hours. After 7 days, the fish meal was changed. Since the fish meal is likely to cause froth bubble disease, it should be fed several times. During the cultivation process, it is best to drain 10 cm of sewage every day from the bottom of the pool, and add new water. Every 10 days, 1 ppm of bleach is used to prevent disease.
After about 30 days of cultivation, the fry generally grows to a size of about 4 to 5 cm in length, and can be placed in large pools for fingerling cultivation.
2.2. Breeding of fingerlings Individual stocks with strong physique, no disease, no injuries, neat specifications, and strong water-returning qualities should be selected. The area of ​​fish breeding ponds is preferably 500-2000 m2, with a water depth of 1.5-2.0 m. After the fish species have been stocked for 7-10 d, they shall be sterilized with quick lime ponds and then used as spares. When stocking, attention should be paid to the temperature difference should not be too large, the weather is clear, when the wind is smaller, the seedlings have better results. Fish seedlings were soaked with 3 to 4% salt water for about 5 minutes. Ponds with stocking densities of 3 to 4 tails/m2, fish ponds with adequate water sources, good water quality, and large water exchange volume can be appropriately increased in stocking density to reach 5-6 tails/m2.
Fish species are best fed with full-grain pellets containing more than 35% crude protein. The fish species began to feed on the third day after the pond, the initial reasons for transportation scared, etc., eating less, it is appropriate to take a small number of multiple feeding, 5 ~ 7d, with the fish species into the normal food, feeding time To reduce it appropriately, every day, every time in the afternoon, the amount of fish fed every day should be about 3% to 5% of the weight of the fish body, and it should be appropriately increased or decreased according to the specific situation. After 10 days, the fish body will be as long as 5~6cm. The principle of feeding is that 80% of the fry are fed and leave.
3. Adult fish farming At present, the artificial breeding of freshwater sharks is mainly based on pond culture, and cage culture is available where conditions permit.
3.1 Pond culture Aquaculture waters should be of suitable area, convenient for drainage and drainage, adequate water supply, and the water quality should meet the fishery water standard, with a water depth of 1.0-2.0m. The ponds should be sterilized in clear ponds in the week prior to planting. Fertilizer water quality, water quality fertilizer, and appropriate water temperature are favorable to the rapid growth of freshwater sharks. Fertilizer after fry under the aquaculture, stocking density for the fry stage put 6 ~ 8 / m3, fish stage put 3 ~ 4 / m3, adult fish rearing 2 ~ 3 tail / m3.
3.1.1 Single ponds 1000 to 3000 m2 can be water depth of 1 ~ 2m, every year from April to May, when the water temperature is above 18 °C, stocking specifications of 5 ~ 10cm seedlings, put 1000 ~ 3000 tails per 667 m2. Use artificial feed or small fish, shrimp, rice bran, etc. to feed.
If feeding artificial compound feed requires tame food, generally it is better to tame food during the period of the flattened piece. That is, when the fish is baited after the fish is stocked, the objects (such as pots, buckets, etc.) may be struck or audible, so that the fish form a conditional reflex. Focus on bait stations to catch food. Normally, it is fed twice a day, about 40% of the diet is fed at about 8 to 9 am, and about 60% of the diet is fed at about 3 to 4 in the afternoon. At the same time, the bait should be flexibly adjusted according to the principles of “four rules†(timing, qualitative, quantitative, and positioning) and “three observations†(see the weather, water quality, and eating habits of fish), and neither waste nor fish. Saturation to ensure that there is sufficient nutrition for the growth of fish.
3.1.2 Polyculture can be mixed with common home fish, tilapia, shrimp, crab, etc. Generally, 60 to 100 tails per 667 m2, 5 to 10 cm in size, without additional feeding, can make full use of pond water space, Improve production and efficiency.
3.2 Cage Aquaculture cages with a volume of 15 to 20 m3 and 50 to 150 tails/m3 of 8 to 10 cm in length are released. In general, 60 to 100 kg of fish can be produced per m3. Must be fed with artificial feed, protein requirements in more than 35%. Generally, the survival rate of aquaculture reaches 80% to 90%, which is lower than the survival rate of pond culture. This is related to the benthic life of freshwater sharks.
Seedling stage can be poured daily soy milk, powdered feed, etc., cast 3 to 4 times a day, after a week can be used to feed red worms, leeches, or artificial pellet feed. When feeding, we still need to do "three look" and "four sets." To be able to eat without being wasted, but the fish is bulimia, and should avoid over-eating, generally every time 80% of fish in the cages eat 80% full, quality and quantity, so that the fish grow faster. In the breeding process, cages are still required to be cleaned frequently to ensure good water exchange, and to prevent escape, theft, disease prevention, and flood control.
4. Disease prevention and treatment Freshwater sharks have strong disease resistance. As long as they are well-prevented and have fewer diseases, their diseases mainly include the following:
4.1 Enteritis disease fish Slow action, do not eat, abdomen enlargement, body color black, anal swelling, light pressure on the abdomen by hand, there is yellow mucus outflow, open abdominal cavity, increased body fluid, intestinal wall congestion, reddish-brown, fasting Black mucus, sick fish died faster, control can use "Allicin", add 0.1 ~ 0.3g per kg of feed fed; can also be used "Fu Ling Ling" 0.2 ~ 0.3g/kg feed added; "Cerberine hydrochloride "Feeding is the most effective. Water body is disinfected every other day with "dichlorohydantoin" or "bromochloroheine".
4.2 white spot disease, also known as small melon worm. On the fish's skin, fins or gills, there are white spots, and a large amount of mucus is secreted. Microscopic examination reveals the small melon body. The medicines used can be used to kill 200g of fish per 667m21m water depth, such as "fish and insect killing"; "insecticide" 0.5mg/l splash; or use "fish and insect clear" 4% added feed to drive insects, The use of fish and insecticides, insecticides, or trichlorfon should be used with caution. The fish is more sensitive to them, and the side effects of the above-mentioned Chinese medicine preparations are less.
4.3 Bubble Disease Freshwater sharks are prone to air bubbles when applying fertilizers such as agricultural organic fertilizers. Under oxygen saturation, seedlings are prone to cause bubble disease. Excessive ammonia-nitrogen gas at the bottom of the pool can also cause air bubbles and cause death. Therefore, fertilizers should be used in water bodies such as "Fei Shui Bao" or nitrogen fertilizer, phosphate fertilizer, and potassium fertilizer mixture. The bottom of the pool should be treated with "bottom net", "ammonia net", etc. In case of lack of oxygen, appropriate amount of oxygenating agent should be used, and less or no oxygen pump should be used. And pay attention to keeping the water fresh and lively, which can effectively prevent the occurrence of the disease.
In addition, trichomonads, third-generation worms, ringworms, etc. may have parasitic fish. Its treatment is similar to white spot disease. A variety of vitamins should be added to the feed, and drugs such as “Allicin†or “Fodamine†and “Fish Health†should be added to prevent the occurrence of fish diseases such as enteritis, skin decay, and acne. Water, such as "Bromochlorohydantoin" and "Chlorine Dioxide", are regularly sprayed on water to prevent bacterial or viral diseases. In the prevention of drugs should be avoided as much as possible the use of side effects of chemicals, such as potassium permanganate, formaldehyde, copper sulfate, malachite green, mercury nitrate and so on. Because freshwater sharks do not have Scales, they are more sensitive to chemical drugs and should use more Chinese herbal medicines for prevention and treatment. However, they should pay attention to the incompatibility of Chinese herbal medicines when they are used. Also note that the concentration of the drug should be slightly lower than that of the ichthyotic fish.
5. Breeding prospects Freshwater sharks have shown great market potential since they were introduced into China. However, they are still breeding in southern provinces and cities such as Guangdong and Hainan, and Hubei, Jiangsu, Sichuan, Chongqing, Zhejiang and other provinces and cities have also cultivated. However, the scale of breeding needs to be improved. Due to the inability of the fish to naturally overwinter in the northern regions of China, swimming in some areas is dominated by only part of the season. The reason for the higher price of the fish is mainly because the seed of the fish is basically imported. How to increase its breeding effect in China will be the main subject of future research on fishery scientists. However, considering the breeding technology, economic benefits, and nutritional value, freshwater white sharks will continue to be active in the aquatic product market in the next few years and will be accepted by more and more consumers.
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