What are the comprehensive prevention and control measures for hemorrhagic disease of farmed fish?

I. Affected species

Grass carp, crucian carp, mud carp, common carp, and even silver carp.

II. Symptoms: punctate or patchy hemorrhages on the head, orbit, fin base, and abdomen of the fish body, gill filaments bleeding or pale, sometimes ascites, and rotting at the ends of fin rays.

III. Causes

1. Fish diseases caused by bacteria are mostly caused by conditional pathogenic bacteria, and will not occur before the water environment has deteriorated. Only when various factors in the substrate and water body become unsuitable for the survival of fish, reducing the fish body's resistance, and at the same time bacteria in the water body multiply in large numbers, will the fish disease break out.

2. Because fish ponds are fed for a long time, the fish excrete large amounts of feces, among which incompletely digested organic matter pollutes the bottom water body, and the pond bottom becomes a hotbed for the massive reproduction of various bacteria. The bacteria, after multiplying in large numbers, decompose organic matter, and the hydrogen sulfide, nitrite, ammoniacal nitrogen, methane, carbon dioxide, and other toxic and harmful gases produced accumulate in the water. Fish living in this environment for a long time will have weakened constitutions, providing an opportunity for bacterial infection.

IV. Disease prevention measures

1. The author particularly emphasizes that @#@233@#@ to improve technology, one must work hard on the word "management" and not neglect even seemingly small links. For fish diseases, one must adhere to the principle of "prevention first, prevention is more important than treatment," and achieve careful management and comprehensive prevention and control.

2. Injection of the "triple vaccine" for grass carp fingerlings is one of the scientifically effective and important preventive measures.

3. Thoroughly clear the pond. From the end of each year to February of the following year, the water temperature is relatively low and fish growth is restricted. This period can be used to dry the pond and remove excess pond mud. It is best to drain the pond water completely and expose the pond bottom to the sun until it turns white and cracks with large fissures.

4. A few days before storing water in the pond, use a large amount of quicklime (lump form), 100-150 kg per mu of pond bottom, or 10-15 kg of bleaching powder, diluted with water and splashed over the whole pond.

5. Before fingerlings are put into the pond, they should be soaked to disinfect the body surface. Commonly used drugs include 3% salt water, 1/10000 potassium permanganate, 2/10000 formalin, and 4/10000 furazolidone. The soaking time depends on the water temperature.

6. Reasonable dense stocking and polyculture, making full use of the water body and feed, and not giving the water body environment a load of fish beyond its capacity.

7. Use medium- and high-grade feed, and use less raw materials (raw bran, corn, @#@245@#@, yellow powder, etc.) and less low-grade feed. In this way, producing the same amount of fish will discharge less feces, thereby easing the pressure on the pond.

8. It is advocated to seine once every 20-30 days. Seine and stir the pond on sunny mornings and at noon, stirring the bottom mud rich in organic matter up to near the water surface. This allows part of the organic matter to be oxidized by the oxygen in the water body, also provides sufficient aeration, and can inhibit the reproduction of anaerobic bacteria.

9. After each seining, immediately disinfect with quicklime at 15-20 kg per mu per meter of water depth, or with other water body disinfectants. Disinfection with quicklime is advocated.

10. In high-temperature seasons, new water should be added frequently, or part of the pond water should be replaced.

11. It is advocated to turn on the aerator at noon on sunny days. In addition to being turned on when rescuing fish from floating at the surface, running the aerator for 1-2 hours between 12:00 and 3:00 at noon on sunny days is also an effective measure to ease the pressure on the pond and prevent disease.

12. Pay attention to pond hygiene, and as far as possible do not discharge unfermented human and livestock manure directly into the pond.

13. Frequently remove weeds. In feeding, follow the "four looks" and "four fixeds" principles, leave no residual feed, and dead fish should be taken out of the pond and buried deep in a pit. The four looks principle: look at the season, look at the weather, look at the water color, and look at the fish's feeding situation. The four fixeds principle: fixed location, fixed time, fixed quality, and fixed quantity.

14. Do not raise a certain species of fish for many years in succession, so as to improve immunity.

V. Treatment methods

1. When fish disease occurs, one should adhere to the policy of "early detection and early treatment." Take treatment measures according to the actual situation, so as to control the expansion of the disease and reduce economic losses.

2. In treatment, comprehensive measures of "external disinfection and internal administration" should be adopted.

3. Treatment has a certain course and duration. Any treatment method that seeks to achieve therapeutic effect through only one water body disinfection or one internal administration can hardly achieve the ideal effect.

4. Water body disinfection by splashing over the whole pond is one of the effective methods. The usual medication time is around 10:00 in the morning, and it can be used two to three times in succession. The first two times can be once a day within two days, or once every other day, and the third time can be used one to two days after the latter medication as appropriate.

5. Some currently selectable water body disinfectants: a. Bleaching powder: 0.4-0.5 kg per mu per meter of water. b. Strong chlorine powder: 0.15-0.25 kg per mu per meter of water. c. Disinfectants whose main components are "dichloroisocyanuric acid" and "trichloroisocyanuric acid" have many trade names. Please choose those produced by legitimate manufacturers and use them according to the instructions. d. Fourth-generation disinfectants, mainly those whose main component is "chlorine dioxide," with trade names such as "Kejunwang," "Jundujing," etc. They generally come in two bags, A and B; A and B must be dissolved separately and then mixed to be effective. e. Quicklime. Quicklime cannot be used at the same time as the chlorine-containing disinfectants a-d above. It can be used 2-3 days after the chlorine-containing disinfectant at 15-20 kg per mu per meter of water to consolidate the therapeutic effect.

6. At the same time, internal medication is generally needed for 4-6 days; the use of sulfonamide drugs takes a little longer.

7. Administration method: if most fish feed normally, take half of the day's feed amount and make it into medicated bait. When feeding, first feed the feed without medicine, then feed the medicated bait. If food intake decreases, medicated bait can be used entirely, and the administration time should be extended as much as possible.

8. Self-made method of medicated bait: correct preparation of medicated bait is a measure to ensure that the medicine is not wasted and that treatment is effective. If pelleted feed is used, there are two preparation methods: first, dissolve enough medicine in water, soak the feed for 1 hour, with the amount of water just enough to submerge the feed. After it is fully absorbed, mix an appropriate amount of flour (not too much) on the outside of the medicated bait to coat the medicated bait, so as to prevent the medicine from being lost, and then let it dry slightly. The second method is to add the materials to a flour paste made from flour, with the flour amount being 5%-10% of the feed amount, spread the flour paste on the feed, then coat it with a small amount of flour.

9. Internal medicines: a. Oxytetracycline: 5-7 g per 100 kg of fish per day. b. Sulfonamide drugs: 10-20 g per 100 kg of fish per day. c. Norfloxacin (2-4 g per 100 kg of fish per day) plus enrofloxacin (99% pure agent), 1-2 g per 100 kg of fish per day; please use with caution. d. Appetite-promoting drugs: yeast tablets, rhubarb, baking soda tablets, etc. e. Chinese herbal medicines: rhubarb, Isatis root, Andrographis paniculata, etc., mixed at 0.5%-1% dosage. f. Do not use a certain medicine for a long time, so as to avoid drug resistance. g. On the first day, the medication dosage can be appropriately increased.

VI. Points for attention

1. Operations can be carried out according to the farmer's own experience and actual situation, but the dosage must not be increased arbitrarily.

2. During the period of water body medication, close attention should be paid to the fish's activity, and the aerator should be run at full capacity to prevent death from hypoxia and floating at the surface or from drug poisoning.