A case of prevention and control of fish outbreak in small reservoir

In early October 2005, fulminant hemorrhagic disease occurred in farmed fish in Tuonan Reservoir of our town. Through our active treatment, the disease was basically controlled. The situation of prevention and control is summarized as follows:

I. basic situation

Tuonan Reservoir normally has a water area of 100 mu and a high water season of 150 mu, with an average water depth of 3 meters and a maximum depth of 6 meters. Artificial culture has been carried out in the reservoir since the early 1990s, mainly conventional fish, including green shrimp, yellow catfish and so on. The water quality of the reservoir is fresh and there is no epidemic history. In recent years, with the continuous increase of stocking density, unreasonable stocking structure, invasion of exotic bacteria, non-disinfection during the release of fish species, and unreasonable drug use in the past two years, fish disease in the reservoir has occurred from time to time. and showed an upward trend, resulting in a large-scale outbreak of hemorrhagic disease in early October 2005.

Second, symptoms of diseased fish

The main symptoms of this disease are silver carp and crucian carp, the symptoms are as follows: congestion in the mouth, head, orbit, operculum epidermis and fin base of diseased fish, mild congestion of muscles on both sides, exophthalmos, abdominal enlargement, anal redness and swelling; dissection of diseased fish, Gill filaments gray and white, sometimes purple, severe Gill end rot, red or yellow ascites in abdominal cavity, enlargement of liver, spleen and kidney, congestion of intestinal wall, no food in intestine.

III. Treatment process

After the occurrence of the disease, 50 million 100 kg of fish died every day, and no measures were taken from October 2 to 5. After on-the-spot investigation, the author took the following treatment measures: first, the fish was sprinkled with high copper in the whole pond, with a water depth of 1 meter per mu, and 15 ml per mu of water; every other day, bromochlorohydantoin strong chloride (1 ∶ 1) + Yudazhuang mixture was used in the whole pond, the concentration of the first two drugs was 0.3mg / L, and the dosage of fish was 50g per mu. After the use of drugs, the dead fish became less and less, and the dead fish basically stopped after 5 days.

IV. Suggest prevention and control measures

In view of the characteristics of the general reservoir, such as relatively large water area, deep water level, high cost of medication, and difficulties in prevention and control, it is suggested that the following comprehensive prevention and control measures should be taken.

1. Strictly disinfect fish fingerling. To resolutely put an end to the fluke mentality, insist on using drugs to disinfect the fish during the release of the fish, using 3%-5% salt water or 10 mg / L potassium permanganate.

two。 Try to reduce mechanical damage when pulling nets and transporting fish species.

3. If the water body mixed culture of green shrimp, river crab, do not use pesticides. If it is really necessary to use, the first choice is the mixture of copper sulfate and ferrous sulfate (5 ∶ 2) or high copper in Yujing to avoid great damage to prawns and crabs as far as possible.

4. If the water body has no history of drug use, it is recommended to sprinkle bleach in the whole pool for prevention, which can greatly reduce the cost of medication, and the preventive effect is also good: if fungicides are used many times, the drug should be changed to avoid drug resistance, and bromine or bromochlorine preparations with little side effects should be used with little effect on water and fish. According to this treatment, dibromohydantoin + bromochlorohydantoin (1 ∶ 1) or fish and shrimp strong chlorohydantoin + bromochlorohydantoin (1 ∶ 1) mixture has a good effect, combined with fish Dazhuang (VC, VE) to enhance fish immunity and speed up wound repair, the effect is better.