Common diseases and prevention measures of bluefish
In the process of breeding bluefish, it is easy to produce diseases such as enteritis, red skin, rotten gills and so on. Different prevention and treatment measures should be taken for different diseases. First of all, we must do a good job in prevention, disinfect water bodies with quicklime, strong chlorine and other water bodies; secondly, do not feed moldy feed, feed green material with bleach powder to disinfect and then feed. If broodstock are found to be sick, they should be diagnosed in time and treated symptomatically.
1. Bacterial enteritis
There are two types of pathogens in blue fish enteritis, one is a parasite, the most harmful is Emmy's coccidiosis; the other is bacterial, bacterial enteritis is very harmful to green fish, especially for grass carp, second-aged bluefish in that year, more serious, some fish pond mortality rate of up to 90%.
1. Symptoms
The anus of the sick fish is swollen and purple-red; the belly of the fish is cut along the midline of the abdomen, and a lot of abdominal fluid often flows out. The bowel tubes are inflamed and red or purple-red. The intestines are filled with blood pus or milky yellow mucus. Pressing the abdomen of the sick fish with your hand, mucus flows out of the anus. At the beginning of the disease, it is only in the vicinity of the anus 6.6 to 10 cm or the esophagus and stomach congestion and inflammation, and then gradually expands until the whole intestine is purple-red. Sick fish generally have no appetite, have a black body color, and swim slowly on the surface of the water at the edge of the pool.
2. Prevention and control measures
(1) Water disinfection: In the season of high incidence of disease, do water disinfection every half a month, using bromochlorohydantoin, dibromohydantoin, chlorine dioxide and other products.
(2) Regulate water quality: During the peak feeding period, the substrate modifier is released every half a month, and the ozone is used at the same time; the next day, the whole pool is sprinkled with high-efficiency bacillus compound preparations, with the use of EM bacteria and yishuining.
(3) Internal sterilization: use compound Enrofloxacin and aquatic V C mixed bait feeding; or use sanhuangshan, aquatic V C, Enrofloxacin mixed bait feeding. 5 to 7 days is a course of treatment.
2. Erythroderma
Erythroderma is more common in large fish aged 2 to 3 years, and it also occurs in fish in that year, often occurring at the same time as enteritis and gill rot, forming complications. It is endemic all year round, especially after fishing and transportation, and injured fish are more susceptible to disease.
Fish body bleeding inflammation, scale shedding, especially on both sides of the fish body and abdomen is the most obvious; the base of the fin is congested, the tip end is rotten, and the borer fin appears; the upper and lower jaws and gill caps of the fish are partially congested, and the middle of the gill cap is sometimes faded or even transparent; most fish intestines are engorged and inflamed. Sometimes ulcers appear in muscle tissue.
(3) Internal sterilization: use Enrofloxacin and aquatic V C mixed bait feeding; or use sanhuangshan, aquatic V C, Enrofloxacin mixed bait feeding; or use allicin mixed bait feeding. 5 to 7 days for a course of treatment.
3. Bacterial gill rot disease
April to October is the epidemic season for the disease. The water temperature above 20 °C began to circulate, the most suitable water temperature is 28 ~ 35 °C, and the water temperature is less common when the water temperature is below 15 °C. The pathogen is mycoccus, which has suitable growth conditions: good growth at pH 6.5 to 7.5, and no growth below pH 6 and pH above pH 8. 0.7% salt water kills this bacterium.
The body color of the sick fish is black, especially the head, so it is also called "aconitum plague". With the aggravation of the disease, the epidermis inside the gill cover of the diseased fish appears hyperemic, and the inner membrane of the middle part is often corroded into round or irregular transparent small windows, commonly known as "open skylights"; the gill lobes become grayish white or white, and the gill lobes are attached to sludge or a large amount of mucus. The gills are rotting with a white tinge of yellow, the tip cartilage is exposed, and there is sludge or mucus, and a large number of slender, glideming bacilli are seen on microscopy.
(1) Water disinfection: In the season of high incidence of disease, do water disinfection every half a month, using bromochlorohydantoin, dibromohydantoin, chlorine dioxide and other products; in the case of water exchange, saline can be used to sprinkle the whole pool.
(3) Internal sterilization: use salt to mix bait feeding, 2 to 3 days to see the effect.
Table salt has a preventive and therapeutic effect on bluefish diseases. Table salt has a strong insecticidal and sterilizing effect, especially in freshwater aquaculture, which is of great significance for the prevention and control of fish diseases. The specific method is: (1) soaking. Soak in 3% saline for 10 to 15 minutes to kill most pathogens and parasites such as intracula, gill whipworm, wheelworm, third-generation worm, and ringworm. (2) Spilling. The water depth is 1 meter, and the salt per mu is 7.5 to 15 kg, which can prevent and control gill disease and red skin disease of green fish.
(3) Mixing feeding. Mixing 2.5% table salt into the compound feed can prevent and treat bluefish enteritis and gill rot. (4) Use with drugs. Use the combination of cessation of water outbreaks, enrofloxacin and table salt, sprinkling, and internal administration, effectively preventing the "three diseases" of greenfish. Salt dosage 5 to 7 mg/L.
