Freshwater sharks (Pangasius sutchi Fowier), also known as Pangasius sutchi Fowier, tiger head shark, sardines, or Bajin fishes, are attached to the scorpion-like head, and are mainly distributed in Southeast Asia. They are Malaysia, Thailand, etc. Excellent freshwater fish in the area. Freshwater shark body color is black, white, gray, red four. The sharks of the first three colors are mostly raised as food fish, and gray sharks are the most popular. Their back is blue, blue on the side of the body, and silvery white on the abdomen. It has fast growth, mixed food, low disease, high yield, and low oxygen tolerance. , adaptability, easy to grasp and other advantages of breeding techniques. Since the introduction of China in 1998, there has been an upsurge of breeding in Guangdong, Hainan, Sichuan, Chongqing, Hubei, Jiangsu and other provinces and cities, showing a huge market potential.
In order to adjust the structure of aquaculture species in the region, expand the proportion of special and superior aquaculture, and increase the output of the â€œShangnongxiayuâ€ pond, we introduced freshwater sharks and local flower whitefish in freshwater in Shandong Province in May 2005. Area polyculture tests have achieved good results, and the results of the aquaculture trials are summarized as follows:
1 Biological characteristics
1.1 Morphological characteristics Freshwater sharks are long, head-conical, short-knee, sub-nasal and inferior, front and rear nostrils far apart, aponeurosis and cheeks are not connected, two jaws with plate-like small teeth, vomer teeth belt separation, The cheekbones connect together. There must be 2 pairs of whiskers and whiskers. The back is obviously raised, the dorsal fin has a stout hard spine, and fat fins. The abdomen is round, without abdominal ridges, and the pelvic fins are small. The posterior extension is accessible to the anus. The pectoral fin is in an upright position with an extremely developed hard spine on the outer edge, and the inner edge of the hard spine is serrated. The body surface is smooth and scaleless, with mucus. There is a flat lateral line from the posterior edge of the lid to the caudal fin base. Fresh individual body is grayish black, belly is silvery white, and the body side has 3 to 4 vertical blue stripes, and the adult fish stripe disappears. .
1.2 Habits and habits Freshwater sharks are tropical fishes that inhabit the middle and lower layers of water bodies under natural conditions. Because of its cockroach's assisted respiration, it often swims to the surface to draw water and directly breathes oxygen from the air. It has strong anti-low dissolved oxygen ability, can survive long-term in the sewage, and has stronger disease resistance and adaptability than other fish. Freshwater sharks are omnivorous fish that are dominated by vegetal foods. They are very bulimia and have a wide range of food choices. Juveniles mainly feed on zooplankton, such as rotifers, flatworms, copepods, and aquatic insect larvae. They can also feed on artificial feeds. From the time of the fishes to the adult stage, the food is more miscellaneous, in addition to feeding various natural foods. In addition, all kinds of commercial feeds, animal waste, vegetables, leftovers, etc. can all be ingested. Under artificial feeding conditions, a large amount of compound feed can be ingested. If there is no specialized artificial feed, tilapia feed can be used instead, and pig manure, chicken manure, and duck manure can also be fed.
1.3 Adaptation to temperature The freshwater shark is a tropical fish. Its optimum temperature range is 20 ~ 33 Â°C, and the optimal growth temperature is 25 ~ 32 Â°C. Its ability to adapt to low temperature is relatively weak, and the temperature at the low temperature is 12 Â°C. In winter in northern China, it is not possible to overwinter over winter and it is necessary to provide overwintering equipment. When the water temperature drops below 18 Â°C, the food intake and activity are significantly reduced. The water temperature falls below 12 Â°C and begins to die. Freshwater sharks have a timid, dry nature and are constantly excited in the water when disturbed by the outside world. Therefore, the breeding environment should be quiet.
1.4 Growth and breeding habits Freshwater sharks grow extremely fast. In the country of origin, Thailand, the largest aquaculture can weigh up to 10 kg, and under appropriate cultivation conditions, it can grow about 1.5 kg per year, and grow faster in natural waters. Commercial fish breeding, breeding cycle 1 to 2 years more economical.
The sexual maturity of freshwater sharks is relatively late. Generally, it takes 3 to 4 years of age, and the body weight is more than 3 kg to reproduce. Each year, from June to September, it is the breeding season. It is a spawning type for 1 year, and each spawns about 300,000 eggs. 700,000 grains, small, spherical, transparent light green, sticky.
2 pond polyculture
2.1 Materials and Methods
2.1.1 Pond Condition The breeding pond has an area of â€‹â€‹5 mu and a water depth of 1.7 meters. The pond is rectangular, with mud bottom, flat bottom and shallow sludge. There is a 3 kW aerator in the pond.
2.1.2 Water source The water source comes from a medium-sized reservoir near the pond. The water source is sufficient and the water quality is fresh. The amount of water-soluble oxygen in the culture is above 5 mg/l, the pH of the water is 7.2-8.1, and the water injection and drainage are convenient.
2.1.3 Feed source The raw materials such as cow dung and pig dung were used in the previous period to provide abundant biological feed, and fed with feed, and feed for fish in the middle and later stages.
2.2 Fish fry stocking
2.2.1 Disinfection of ponds Before the fishes are used in the lower pool, disinfect with 100kg/mu of clear lime in the clear pond to remove the predator organisms, wild fish and pathogens in the pond.
2.2.2 Bait preparation The fish seedlings are used to ferment 150 kg/mu of fermented cow dung 7 to 10 days before the lower pond to breed natural bait so that there is a rich bait behind the fish pond. When the fish is under the pond, the pool water is dark brown or oil green, and the transparency is about 30 cm.
2.2.3 Fangmiao On April 1, 2005, 2000 white-billed seedlings purchased from a nearby seedling plant were planted at an average length of 10 cm. On May 7, 2005, 2000 freshwater sharks were purchased from the Shandong Institute of Freshwater. The average body length is 10 cm.
2.3 Daily Management
2.3.1 Water Quality Management Water quality requires fat and cool, not muddy, when the pool water is too thick, yellow, white or black, change new water in time, change the water every time by about 30 cm, so that the transparency of the pool water is kept at 30 cm all year round. about. When the weather changes, aerators can be opened in time, or quicklime can be used to regulate water quality. Analytical determination of water samples was performed daily, including water temperature, salinity, DO, pH, transparency, water depth, and water color (see Table 1).
Table 1 Water temperature (Â°C) Specific gravity DO (mg/l) pH water depth (m) Water transparency (cm)
24.3 to 31.4 1.008 to 1.012 5.1 to 7.8 7.3 to 8.5 1.5 to 2.1 Light brown or light green 25 to 35
2.3.2 Fertilization and Feeding Fertilization Fertilizer or biological agent is applied once every 25 days to keep the amount of bio-litter in the tank adequate. Feed the fish with bait twice a day, ie at 10:00 a.m. and 16:00 p.m. once a day, and the amount of bait per day is 3% to 5% of the fish's body weight. When feeding the feed, it should adhere to the â€œthree observationsâ€. Four set."
2.3.3 Inspecting the patrol pond The patrol basin is inspected twice a day, in the morning and in the evening, to observe the activity of the fish. When the weather is hot or melted, new water is added and the aerator is started to avoid floating heads. If any problems are found, take timely measures.
3 Disease Prevention and Control
3.1 Enteritis Disease Fish are slow to move, do not eat, abdomen enlargement, body color blackening, anal swelling, gently press the abdomen by hand, there is yellow mucus outflow, sick fish die faster. "Allicin" can be used to feed 0.1 to 0.3 grams of feed per kilogram of feed. It is also possible to use furazolidone to feed 0.2 to 0.3 grams per kilogram of feed.
3.2 White spot disease is also known as small melon worm disease. On the fish's skin, fins or gills, a small white spot can be seen, and a large amount of mucus is secreted, and the small melon body can be observed by microscopic examination. Can be used to kill fish, kill 200 grams per acre; or use 40% "fish and insect clear" feed to feed insecticide.
3.3 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 air bubble disease. Excessive ammonia-nitrogen gas in the bottom of the pool can cause air bubbles and cause death. Therefore, in the water body fertilization should use nitrogen, phosphorus, potassium compound fertilizer mixture. The bottom of the pool should be treated with "bottom net", "ammonia net" and other treatments. In the absence of oxygen, the appropriate amount of oxygenating agent should be used, and less or no oxygen pump should be used.
No fulminant disease occurred during the whole culture experiment. Fish species were soaked with 3% saline for 10 minutes before stocking. During the growing season, the bait is fed once every two weeks (50 kg of feed plus 25 grams of oxytetracycline, twice daily, for three days). In addition, fertilizers and baits, tools, etc. are often disinfected with bleach.
4 Results and Discussion
4.1 Results From the middle of September, the harvest was completed, and the harvest was completed on November 1. A total of 1,779 freshwater sharks were harvested, with an average weight of 810 grams and a total of 1441 kilograms. There were 1,876 white pelicans harvested and an average weight of 1,256 grams, a total of 2356.2 kilograms.
4.1.1 The cost of seedling fees and seed transportation costs 7126 yuan, fertilizer fee 570 yuan, bait fees 18 226.6 yuan, utilities 850 yuan, drug costs 282 yuan, labor costs 5323 yuan, pond rent 600 yuan, other costs 3230 yuan A total of 36207.6 yuan.
4.1.2 The output value of freshwater sharks is 60 522 yuan; Baiyun is 10 367.5 yuan; total income is 70 889.5 yuan.
4.1.3 Benefit Analysis The total income is 70 889.5 yuan, the total investment is 36 207.6 yuan, and the net profit is 34 681.9 yuan. The average profit per mu is 6936.4 yuan, and the input-output ratio is 1:1.96.
4.2.1 Experiments show that during the period from mid-May to early October, freshwater shark farming in the northern region is completely feasible, and the growth rate is fast, the survival rate is high, and high yield and high efficiency can be achieved.
4.2.2 Freshwater shark has strong resistance to diseases and no disease occurred during domestication.
4.2.3 The polyculture of freshwater sharks and whitefishes not only improves the three-dimensional application of water resources, but also improves the utilization rate of the bait. It is a new mode of utilization of the â€œShangnongxiayuâ€ pond in the Yellow River beach area.
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