1, water and salinity
Because of its wide salt compatibility, tilapia can generally be placed directly in waters with a salinity below 1.8%. Therefore, many low-salinity ponds in the sea are also used for the cultivation of tilapia. Practice has shown that tilapia grows faster in brackish water or seawater than in freshwater, and its specifications are relatively large and the production effect is also better.
The time of fry survival in salt water bodies is related to the size and salinity of the fry. The smaller the fry, the lower the tolerance to salinity and the shorter the survival time; the higher the salinity, the lower the tolerance of the fry, Therefore, the aquaculture body must consider proper salinity.
2, stocking requirements
Tilapia species that are hatched in fresh water cannot be put directly into high salinity water bodies and must be gradually adapted before they can be released. Generally, tilapia seedlings with a total length of 1-2 cm can be preserved in brackish water with a salinity of about 0.5%, and then the salinity of the holding tanks can be increased by about 0.3% every day until the salinity is approached. Only officially put into the pool for stocking.
During domestication, little or no bait should be given to prevent dehydration of the viscera due to excessive salt intake. In addition, due to the high pH value of seawater, the stomach and fish of the fish are not adapted to foods with high pH, ​​and digestive juices in the gastrointestinal tract are neutralized and cause indigestion. At this time, fish body weight loss and weight loss often occur, but as the fish's ability to adapt to high salinity increases, this phenomenon will gradually disappear, and normal activities will be restored, and then gradually increase the amount of feeding.
Generally domesticated tilapia can be cultured in salinity seawater below 3.0%. The farming methods can also be divided into monocultures or polycultures. For single-cultivation, 4 to 50 thousand species of fish are usually placed at about 5 cm per hectare. Mixed breeds can be salmon, barracuda and marine shrimp. Stocking densities and polyculture ratios can be determined based on pit conditions, species supply, and feed availability. For tilapia-based ponds, about 10,000 tilapia species can be placed at 5-7 cm per hectare, and about 5,000 species of squid and barracuda are available. When tilapia is used as the main source of mixed carp and barracuda, 12,000 tilapia species are stocked at 5-7 cm per hectare and about 8,000 species of carp and barracuda are stocked. When stocking, look at the supply of water and increase it slightly.
3, daily management
To inspect the ponds and grounds, observe according to the unified requirements of the Ministry of Agriculture, and do a good job in the records of aquaculture production and records of aquaculture medication. Special attention must be paid to the floating heads of other fish in mixed ponds. It is impossible to fertilize at rainy or low pressure and reduce feeding at the same time to prevent flooding. An aerator must be installed in the large-scale breeding. The start-up and running time of the aerator must be determined according to the weather, fish activity and other conditions. From time to time, fish cultures should be sampled to detect problems and strengthen management.
Before the fall outdoor water temperature dropped to 18°C, the fish moved into the wintering pool. When the outdoor water temperature in the spring rose back and stabilized above 20°C, the fish could be removed from the wintering pool. The wintering pool is a cement pool or earth pool, close to the water source, sheltering from the sun. The indoor pool area is 10-50 square meters and the pool depth is 1.5 meters. Before the fish enters the pond, the dirt on the bottom of the pool should be cleaned, and the walls of the pool and the bottom of the pool should be disinfected with drugs that meet the requirements of environmental protection.
During winter, the water temperature is maintained at about 18°C. According to the change of water quality, the water should be changed regularly or be replenished with new water. Dissolved oxygen in the pool water remained above 3 mg/l. The stocking time of tilapia in seawater or brackish water is stable above 18°C.
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