Freshwater sharks, also known as Pangasius, tigerhead sharks, sardines, or Bazhen fishes, are mainly distributed in Southeast Asia. They are newly introduced freshwater species. The key farming techniques are now described as follows:
First, biological characteristics
1, body type and body color. Freshwater shark body color is black, white, gray, red four. The sharks of the first three colors are mostly kept as food fish, and grey sharks are the most popular. Their back is blue, blue on the side of the body, and silvery white on the abdomen; red sharks are crystal puddles and are mostly kept as ornamental fish.
2, adaptability and food habits. Freshwater sharks are resistant to hypoxia and have wide adaptability, but they have low resistance to low temperature. The optimum temperature is 20°C-34°C, and the optimum growth temperature is 26°C-32°C. When the water temperature is lower than 18°C, the activity is slow and unresponsive; when the water temperature is lower than 12°C, it begins to die. The fish has a more complex diet. Juveniles use zooplankton as feed. Adult fish feed on aquatic plants and artificial compound feed. The feed protein requirement is 28%-32%.
3, growth and reproduction. Freshwater sharks are omnivorous, have a large food intake and grow fast. The fry (3 cm-4 cm) was farmed for 4 months and the body weight was more than 0.6 kg. The fish is more mature and can breed for 3 to 4 years, weighing more than 3 kilograms. The breeding season is April-September and it is a one-time spawning fish.
Second, aquaculture technology
1, the pond is raised. The pond area can be between 1 mu and 10 mu, with a water depth of 1.2 to 2 meters. From April to May each year, when the water temperature is stable above 18, the stock size of 5 cm to 10 cm can be stocked, and stocked per mu. The amount is generally 1000-2000, and the stocking capacity of the pond with good conditions can reach 2000-3000. Feeding artificial pellet feed, feeding twice a day, the feeding amount is 3%-5% of the fish's weight.
2, pond polyculture. It can be mixed with other four species of fish, tilapia, catfish, shrimp, and crabs. Generally, the amount of polyculture on the water surface per mu is 100 to 200 (5 cm to 10 cm in size). No additional feed is needed. .
3, cage culture. The cage size is generally 4m 4m 2m or 5m 5m 2m. The effective breeding water body is 25m3 - 45m3, and the stocking size is 8cm - 10cm and 100 species - 150/m3. Feed artificial pellet feed, feed protein requirements 28% -32%, preferably floating water feed.
Third, feeding and management
1, feed and feeding. Newly hatched fish fry use aquatic animals and plants as baits, which can be cultivated by means of rearing four fry fish fry. If the cement tank is used for breeding, it can be fed with leeches or squid feed. When the larvae grow to more than 5 cm, they can feed the nutritious pellet feed. Adult fish breeding mainly to feed particles. The grain size of the pellets fed at each stage should be compatible with the caliber of the fish. They should be fed twice or three times per day, and the daily feeding amount should be 3%-5% of the body weight of the fish. When feeding feed, it should be "three look, four set."
2, disease and prevention. The practice of breeding shows that freshwater sharks are more sensitive to chemical drugs. Therefore, chemical drugs with strong irritation and high side effects should be avoided during feeding. In the epidemic season of fish disease, regular spillage of drugs containing “chlorine†or the addition of “allicin†and “oxytetracycline†to feeds will prevent the occurrence of bacterial or viral viruses. In the stage of fry, it is easy to infect parasitic diseases such as small worms and trichotomous worms. If suffering from skin diseases such as skin skin, acne and other skin diseases, 20 micrograms/gram of formalin can be used to splash and keep the efficacy for more than 2 hours.
Sprinkler irrigation and micro-irrigation automatic control equipment With the development of economy, water resources, energy shortage and labor cost increase, more and more water-saving irrigation systems will adopt automatic control. This article focuses on the advantages and classification of automated irrigation.
The advantages are as follows:
(1) It is possible to truly control the amount of irrigation, irrigation time and irrigation cycle in a timely and appropriate manner, thereby increasing crop yield and significantly improving water utilization.
(2) Saving labor and operating expenses.
(3) The work plan can be arranged conveniently and flexibly, and the management personnel do not have to go to the field at night or other inconvenient time.
(4) Since it can increase the effective working time every day, the initial capital investment in pipelines, pumping stations, etc. can be reduced accordingly.
classification:
First, fully automated irrigation system
The fully automated irrigation system does not require direct human involvement. The pre-programmed control procedures and certain parameters that reflect the water requirements of the crop can automatically open and close the pump for a long time and automatically irrigate in a certain order. The role of the person is simply to adjust the control program and overhaul the control equipment. In this system, in addition to emitters (heads, drip heads, etc.), pipes, fittings, pumps, and motors, it also includes central controllers, automatic valves, sensors (soil moisture sensors, temperature sensors, pressure sensors, water level sensors, and rain sensors). Etc.) and wires.
Second, semi-automatic irrigation system
In the semi-automated irrigation system, no sensors are installed in the field. The irrigation time, irrigation volume and irrigation period are controlled according to pre-programmed procedures, rather than feedback based on crop and soil moisture and meteorological conditions. The degree of automation of such systems is very different. For example, some pump stations implement automatic control, and some pump stations use manual control. Some central controllers are only one timer with simple programming function, and some systems have no central control. The controller, but only some of the sequential switching valves or volume valves are installed on each branch pipe.
Automated irrigation is the trend of the times. In the future water-saving irrigation projects, more and more automated irrigation systems will be applied.
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