In the past two years, more and more people have been farming mandarin fish, and at this stage, large-scale aquaculture is being carried out in Guangdong, Jiangsu, Zhejiang, Hubei and Hunan on the mainland. During the market visit, several problems in the intensive culture of mandarin fish were briefly analyzed.
Under natural conditions, mandarin fish like to live in a still water or micro-flowing water and clean and fresh water, so it is believed that the clearer the water quality of the aquaculture pond, the greater the transparency, the better, so in order to keep the water quality of the intensive mandarin fish pond fresh and not fertilize for a long time.
However, in the environment of artificial culture, after high-density aquaculture, the metabolism of bait fish and mandarin fish increases, the plankton biomass in the lean water body is relatively small, the material and energy circulation is not smooth, and the residual bait and feces cannot be converted into nutrients used by algae in time, so that the metabolites continue to accumulate, producing a large number of toxic and harmful substances such as ammonia nitrogen, nitrite, hydrogen sulfide, etc., breeding a large number of pathogenic microorganisms and endangering the health of mandarin fish.
Second, mandarin fish fry above 2.5cm are prone to ciliate diseases such as wheel worms and oblique tube worms during the cultivation process, and some nursery farms use a lot of irritating insecticides to control and control parasites, which aggravates the pressure of seedlings and increases the probability of suffering from viral diseases. Mandarin fish is sensitive to most conventional drugs, especially organophosphorus insecticides, heavy metal salts and halogen chemical disinfectants.
These drugs have strong corrosive and toxic effects, while killing insects and sterilization, cause inflammation of the gill tissue of mandarin fish, affect the normal breathing of mandarin fish, destroy the mucus protective layer on the body surface of mandarin fish, thereby opening the door to the invasion of various pathogenic microorganisms, and if used in the mandarin fish fry stage, it is easy to cause fish deformity.
In addition, the use of these strong irritating drugs has a strong killing effect on plankton in the water body, which is easy to cause thin water quality, and will also have adverse effects on mandarin fish feeding, resulting in a decrease in mandarin fish resistance and infection with diseases, forming a vicious circle.
Therefore, in mandarin fish culture, algae should be maintained, the water color should be kept light green, and the transparency of 30cm should be appropriate. The water quality is fertile, the dissolved oxygen is sufficient, and the water environment is stable, which can effectively avoid the stress of the fish body and reduce the incidence of viral diseases. In aquaculture production practice, grass and fertilizer can be piled in a corner of the pond, so that the water quality cultivated is long-lasting, and attention should be paid to reducing the water quality of fertilizer cultivated with ammonium carbide, urea and other chemical fertilizers.
During the production process, a certain number of filter-feeding fish such as tarpon and silver carp can be appropriately set to maintain the normal material and energy circulation in the pond, maintain the good water color of the pond, and provide a good water quality environment for the healthy growth of mandarin fish. For parasites, some plant-based eucalyptus essential oil can be used for prevention and control to reduce the chance of parasite infection.