Main diseases and control of Pseudosciaena Crocea

I. bacterial diseases

1. Vibrio disease

Pathogen: Vibrio parahaemolyticus.

Symptoms: ulcers on the body surface of diseased fish are typical features of the disease. In the early stage of the disease, there are petechiae, ecchymosis and irregular erythema on the body surface, which are more common in the abdomen and tail. In severe cases, the lower jaw bleeding, ulcer, fin base congestion and redness, fin strip defect, caudal stalk muscle decay, the formation of hemorrhagic ulcer. The liver, spleen, kidney and intestine are congested, the liver is enlarged and yellowish mucus is found in the intestine. Microcurved bacteria could be seen in the focus tissue under microscope.

Epidemic: the disease is the most common disease in large yellow croaker. It occurs from March to October every year, and it is common after 6 months, with a body weight of about 80 grams. The time of onset is long, the infection is rapid, and the mortality rate is high.

Prevention and treatment methods: ① oral norfloxacin, ofloxacin and other antibacterial baits, adding 2 grams per kilogram of feed, the course of treatment is 3-7 days. ② formalin 200ml / m3 plus norfloxacin and other antimicrobials 20g / m3 seawater oxygenated for 20min. ⑧ each cage with "chlorine-rich" 1 piece hanging bag, at the same time take "Fish Health No. 1" or "Fish Health No. 1 ~ 2000", according to the dosage of the instructions.

two。 Bacterial enteritis

Pathogen: intestinal type Aeromonas punctata.

Symptoms: at the initial stage of the disease, there were no obvious symptoms on the body surface of the diseased fish. The typical symptoms in the later stage were anal redness, abdominal distension and ascites. Anatomy found that the intestinal congestion and inflammation was purplish red, the intestinal wall elasticity was poor, there was no food or a small amount of food in the intestinal tract, and there was a lot of yellow mucus.

Epidemic: the peak of epidemic is in summer and autumn, the course of disease is short, the mortality rate is high, and the mortality rate can reach more than 80% within 3 to 5 days.

Prevention and treatment: prevent vibrio disease. Treatment: do not use medicine bath, first stop eating, then a small amount of bait, plus appropriate amount of antibiotics treatment. ① oral norfloxacin or berberine hydrochloride bait, every kilogram of feed added 2-4 grams of medicine, the course of treatment of 3-5 days, the first day dose doubled. ② each cage with "chlorine-rich Ⅰ" 1 piece hanging bag, and oral "Fish Health No. 1" or "Fish Health No. 1-2000" and "Aquatic Special Vc" bait, every kilogram feed added "Fish Health No. 1" or "Fish Health No. 1-2000" 20 grams and "Marine Fish Duowei" 2 grams for 3 days. When the disease is serious, bait should be given continuously until cured for another 2 days to consolidate the efficacy.

II. Parasitic diseases

1. Starch egg whipworm disease (also known as starch egg dinoflagellate disease)

Pathogen: eye starch egg whipworm, also known as eye point starch egg dinoflagellate.

Symptoms: the parasite is mainly parasitic on the gills, skin and fins of fish. Many small white spots are visible to the naked eye on the gills; the skin on the body surface is inflamed, bleeding, and even ulcers. The sick fish are restless and swim up and down, rubbing the net with their bodies.

Epidemic: the popular seasons are from March to June and from September to October. From March to June, the disease mainly occurred in parent fish, larvae and juveniles, and the water temperature was 18-25 ℃. From September to October, it mainly occurred on Pseudosciaena Crocea cultured in soil ponds, and both seedlings and cultivation could be infected, and the water temperature of the disease was 2529 ℃. Acute onset, rapid spread and great harm often cause a large number of deaths of Pseudosciaena Crocea. The degree of the disease is mild in the low-salt area of the estuary. The occurrence of the disease is related to the fact that the pathogen is directly brought into the seedling pond by copepods or sand filtered water and the cross-use of seedling tools.

Prevention and control method: reduce the specific gravity of seawater to less than 1.01 to prevent the reproduction of the pathogen. Main treatment: ① fresh water washing diseased fish for 5 minutes, repeated every 3-4 days. ② copper sulfate 10g / m3 fresh water for 10 minutes for 15 minutes for 4 consecutive days. Or use the mixture of copper sulfate and ferrous sulfate (5 ∶ 2) to increase oxygen and wash for 10 minutes.

two。 Stimulation of cryptonucleosis (also known as white spot disease of marine fish)

Pathogen: stimulate cryptonuclei, also known as "sea water melon insects".

Symptoms: the worm is mainly parasitic on the body surface, Gill, cornea and oral cavity of the fish. In the early stage of the disease, the fish body is itching due to stimulation and rub the bottom of the pool, the wall, the net or jump up and down the water. In the middle stage of the disease, the secretion of mucus in the parasitic place increases, and many small white spots can be seen with the naked eye; in severe cases, the body surface is covered with a white film, and some are blind on one or both sides, sick fish do not feed, have difficulty breathing, suffocate to death, or secondary infection leads to death. Microscopic examination of the white spot or Gill mucus, generally each visual field has 5 to 8 worms can be diagnosed.

Epidemic: the peak of epidemic is from May to August. Fry, adult fish and spawning parent fish can all be infected, and the incidence rate is the highest in the seedling stage. Cage culture is most likely to occur in areas where there is no flow or poor water flow, poor water quality, rich organic matter and high density culture. In pond culture, the water exchange rate is low, and the ponds with serious water pollution are the most likely to occur.

Prevention and treatment methods: reduce stocking density, disinfect regularly and improve water quality. Soak ① in fresh water for 5 minutes. ② formalin 200ml / m3 seawater aeration for 20 minutes, or 20g / cu m medicine bath for 20 hours, thoroughly change the water or pour the pool. ⑧ is washed with copper sulfate 10 g / m3 fresh water for 10 minutes. ④ uses carbendazim 60cm 100g / m3, pulls the net to one side in the early morning, and mentions that it is sprinkled evenly about 0.5m above the surface of the water for 20min, or soak the fish in a canvas bag, but need to be inflated with aerator.

3. Valvular disease (also known as white spot disease)

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