Original report of China Aquatic Products Channel,
Sharing of major pest control in the rearing stage of California sea bass fry
<b>Finishing/Mandarin Perch Frontier Li Xiaoxin</b>
This article is compiled from the mandarin perch frontier no. 3 open class "California perch fry breeding stage of the main pests and diseases and control", the course guest is the Chinese Academy of Fishery Sciences Pearl River Fisheries Research Institute Jiang Lan researcher, long press to identify the following picture QR code can review this course.
<b>01 Bullet virus disease</b>
The viral disease during the California perch seedling period is mainly a bullet virus, and the water temperature of the disease is generally 18-25 °C, which mainly infects the juveniles of California perch (2 cm-6 cm).
The typical clinical symptoms of sick fish are lethargy, spiral or irregular swimming, abdominal swelling, and some diseased fish can see emaciation or even curvature. Autopsies revealed whitish gills, enlarged liver and possibly bleeding spots.
Whether it is the seedling stage or the adult fish farming stage, there is currently no drug that can effectively control the disease of viral diseases, mainly to prevent, once the disease needs to be "prevention and treatment" thinking to control the further deterioration of the disease.
<b>Precautionary approach</b>
1. Thoroughly clear the pond and disinfect the water source.
2. Purchase high-quality seeds, and at the same time, it is best to conduct virus detection on broodstock and fry to ensure that there are no harmful pathogens and reduce the risk of follow-up breeding.
3. Vaccination is the most effective way to prevent viral diseases, but at present, the vaccine for California perch is not commercially produced and used.
<b>Control method</b>
1. Maintain a good and stable water quality environment and reduce the stress response of diseased fish;
2. The use of mild disinfection drugs to disinfect the aquaculture water body to control bacterial secondary infection, many times the death of fish with virus is closely related to the large outbreak of death caused by bacterial secondary infection;
3. Feed Chinese herbal medicine and other immune enhancers to enhance the resistance of fish.
<b>02 Bacterial white skin</b>
In recent years, the most discussed is the mature body disease in the cultivation stage of California perch, but "mature body" is only a manifestation of the disease. Mature body disease is not equivalent to bacterial white skin, and some of them are caused by the aforementioned bullet virus, and the diseases and prevention and control methods of bacterial and viral white skin are not the same.
Bacterial white skin is endemic in early spring, the onset of water temperature is about 20 °C, mainly infected with California perch juvenile (2 cm-10 cm); highly contagious, high mortality.
1. Thoroughly clear the pond and disinfect the water source;
2. Feed high-quality bait to improve the resistance of the fish body.
<b>Treatment</b>
1. Maintain a good and stable water quality environment and dissolved oxygen volume;
2. Topical sterilization and disinfection drugs, such as: sodium trichloroisocyanurate, valeraldehyde + benzalkonium bromide mixture, etc.;
3. Internal administration of antibacterial drugs, such as neomycin sulfate, enrofloxacin, etc.
<b>03 Bacterial enteritis</b>
Enteritis is a common bacterial disease during the seedling period, the abdomen of the sick fish is expanded, the anus is red and swollen, the entire abdomen to the jaw area is dark red, and the light yellow ascites flowing from the anus can be seen in the severely ill fish. The main cause of the disease is caused by the spoilage or unclean feeding of feed, so it is acute and harmful.
<b>Prevention and control methods</b>
1. Do not feed spoiled or unclean feed, especially during the change of material;
2. Regularly add allicin to the bait for prevention;
3. When the disease occurs, it is fed with doxycycline, neomycin sulfate and other mixed feed for 45 consecutive days, and good results can be received.
<b>04 Wheelworm</b>
Wheelworms belong to the ciliate class, mainly parasitizing on the gills of fish, but there are also fish bodies, but the problem of wheelworms parasitizing on gills at the fry stage is larger. Because the fry is originally small, the size and capacity of the gills are also very small, if a large number of parasites are parasitized, it will seriously affect the breathing of the fry, the harm is very large, if not treated in time, it will cause a large number of deaths.
<b>Wheelworm staining tablets, reverse view</b>
<b>A large number of wheelworms parasitize the fins of fry, and the opposite is viewed</b>
1. Before stocking fry and fingerlings, thoroughly disinfect the pond with quicklime and bleaching powder.
2. Before the seedlings are stocked, soak in 3-5% salt water (100 kg of water plus 3-5 kg of table salt) solution for 5-10 minutes.
3. Regularly sprinkle zinc sulfate powder, 0.2-0.3 grams per cubic water body, once every 15-20 days.
1, 0.7ppm copper sulfate and ferrous sulfate (5:2) mixture of the whole pool sprinkling.
2, per acre per meter of water depth with fresh neem leaves 35 kg of boiling water sprinkled throughout the pool.
<b>05 Ringworms</b>
Ringworms are mainly parasitic in fish gills, but can also parasitize on the surface of the body. On the one hand, ringworms will absorb organic matter such as blood or mucus on gills as nutrients; on the other hand, ringworm anchors and hooks will cause gills or body surface damage, causing bacterial secondary infection, resulting in the death of fry.
<b>Diagnostic methods</b>
Microscopic examination of gills or mucus on the surface of the body reveals a large number of parasites.
1. When the fry are released, use potassium permanganate (10-20 g/m3) to soak (15-25 minutes) and then go down to the pond.
2. Sprinkle the whole pond with 90% crystallized dimethoates (333-666 g/mu), repeat the drug every interval of 2-3 days, once or twice.
<b>06 Nutritional disorders</b>
"Diabetes" refers to the low utilization of sugar in California perch, and the accumulation of sugar can cause liver damage. At the seedling stage, everyone may pay less attention to the so-called "diabetes", but if the compound feed used at the seedling stage is not of high quality, this problem will also occur, but there will be no obvious liver lesions, which will have an impact on the later stage of cultivation.
Therefore, it is recommended that we must also pay attention to the quality of compound feed at the seedling stage, so as to cultivate robust seedlings and reduce the risk of disease in the later breeding stage.
<b>07 Summary</b>
1. Strengthen the early prevention and control of parasitic diseases
Parasitic infections can cause damage to the gills or body surface of fish, which can lead to bacterial secondary infections and cause a large number of deaths, so the early prevention and control of parasitic diseases should be strengthened.
2. Strengthen disease prevention and control
It is necessary to monitor some specific pathogens, especially viruses, to ensure that the purchased seeds do not have specific pathogens, and reduce the risks in the later stage of seedling cultivation and breeding.
3. Strengthen breeding management
Strengthen feeding management, especially water quality control and sewage treatment. Aquaculture is a kung fu job, which needs to be observed every day, and abnormal phenomena should be dealt with in time.
Water quality control means that the conditions of various factors in water quality should not change too much, otherwise it is easy to cause the stress response of seedlings; the pond balance is broken, which may also lead to a large number of disease causes, resulting in disease occurrence. When sewage treatment, it is necessary to disinfect the discharged water to avoid cross-infection.
4. Rational use of drugs, the right medicine
Rational use of fishing drugs, the right medicine. The long-term use of drugs will make the pathogen develop resistance, so do not use the same drug repeatedly when taking drugs, it is recommended that whether it is an insecticide or an antibacterial drug, try to choose 1-2 kinds, rotate every 3 months, and avoid the emergence of drug resistance.
5. Correctly grasp the dosage, course and method of administration
Long-term use of drugs with insufficient doses, the pathogen will be easy to tolerate, so it is necessary to correctly grasp the dose to completely eliminate the pathogen. The use of drugs is a course of treatment, which must reach a certain time and frequency.
In addition, we should also pay attention to the method of medication, external drugs must be evenly sprinkled, if poured into a local area and other drugs slowly spread, it will cause the concentration of drugs in the local area to be too high, and the concentration of drugs in the peripheral area is too low, resulting in local areas may still be risky, and the peripheral areas cannot achieve the effect.
Internal drug mixture needs a binder, RAW drug mixture if there is no good adhesive, easy to lose after going to the pond, can not be well eaten by fish, can not achieve the effect, so it is recommended that you still buy finished drugs.
There is also a wonderful interactive exchange session in the class, the specific content will be released in the near future, please pay attention to the frontier of mandarin perch.