Prevention and control techniques of common diseases of freshwater fish in spring

The water temperature began to rise in spring, and a variety of bacteria and parasites that could cause disease in fish began to multiply in large numbers. At the same time, fish had a weak physique during the overwintering period, had relatively poor resistance to pathogenic factors, and was easy to be infected with various diseases, causing a large number of deaths of pond fish, causing great losses to farmers and seriously affecting the growth of surviving individuals in the later stage. Therefore, to do a good job in the prevention and control of fish diseases in spring is the key to increase production in aquaculture throughout the year. Based on years of production practice, the author briefly describes the prevention and control methods of common fish diseases in spring as follows, for reference to breeders.

1. Preventive measures

1. Improve the aquaculture water environment and carry out water disinfection prevention.

During the overwintering period, the metabolic wastes of all kinds of aquatic organisms accumulate in the water because the ponds seldom change water. When the water temperature rises in spring, these metabolic wastes begin to decompose, consuming a large amount of dissolved oxygen in the water, and the toxic and harmful substances produced will increase the probability of fish being infected with various diseases. Therefore, after entering spring, in addition to the proper change of water, the application of "Zhongshui Yishuining" or "Yujing good water element" every 10 ~ 15 days can effectively improve the water environment of fish. In addition, in early spring, various biological pathogenic factors such as bacteria, parasite spores and cysts are still in the early stage of reproduction and development, and the insecticidal and sterilization effect is better, which can get twice the result with half the effort. Copper sulfate and ferrous sulfate powder Ⅰ 0.6ppm~0.7ppm or trichlorfon and phoxim powder 0.12ppm~0.3ppm can be sprinkled regularly to prevent protoparasitic fish diseases. Spraying 20ppm quicklime or 0.02ppm bromochlorohydantoin in the whole pool at regular intervals can effectively prevent bacterial diseases.

2. It is necessary to start eating early, strengthen the physique of the fish, and pay attention to improving the resistance of the fish.

Fish overwintering for a long time without feeding, physical consumption is large, poor resistance, very easy to be attacked by pathogens. Therefore, after the water temperature begins to rise in spring, it is necessary to start eating early, feed better formula feed to strengthen nutrition, and according to the number, body size and feeding capacity of eating fish, gradually increase the amount of feeding in the case of rising water temperature. to do the right amount of feeding. At the same time, a part of nutrition and immunomodulators can be regularly added to the feed, such as vitamin C sodium powder, immune activity growth promoter and vitamin E, etc., which can quickly restore the physique of fish and enhance the physique of fish. improve the self-immunity of fish and the ability to resist the invasion of diseases, can effectively prevent the occurrence and epidemic of diseases.

2. Characteristics and treatment of spring fish disease

The epidemic characteristics of fish disease in spring are as follows: first, due to frostbite or pond separation, stocking and other operations, resulting in fish damage, bacterial and fungal fish disease caused by harmful pathogenic bacteria. Second, after the overwintering period, the physique of fish is weak, and at this time, various pathogens or their spores, resting eggs and larvae develop rapidly and reproduce in large quantities with the rise of water temperature in spring, so that the number of pathogens in the water increases rapidly. it increases the chance of contact between fish and pathogens, which is easy to cause parasitic diseases. The common bacterial and fungal fish diseases in spring are water mildew, vertical scale disease, red skin disease, bacterial Gill rot disease, furunculosis; parasitic diseases are mainly fish wave bean disease, oral filariasis, oblique tube disease, melon disease, anchor head disease and Chinese oyster disease and so on.

(1). Bacteria, fungal fish disease

1. Water mildew. Symptoms of water mildew disease: the disease is caused by mold infection, the main symptoms are white cotton hyphae growing in the wound, loss of appetite of diseased fish, restlessness in the water, frequent friction with other solids, muscle decay and slow swimming in the affected area. and finally died of exhaustion.

The first treatment can be washed with 3%-5% salt water for 15 to 20 minutes, or sprinkled with 500ppm salt and baking soda mixture throughout the pool. In the second method, 2ppm~3ppm methylene blue was sprinkled in the whole pool, once every 2 days, and then sprinkled with 0.2ppm~0.3ppm hydantoin drugs 5 days later.

two。 Vertical scale disease. The disease is a kind of disease caused by the accumulation of liquid in the scale sac caused by dirty water quality and bacterial infection caused by fish injury. Fish are very popular in winter and spring and the mortality rate is very high. The main symptoms are that the scales of the diseased fish stand upright, the body surface is rough, and the vertical scales open outward. Press with your hands and liquid is ejected from the scales, and the scales fall off.

For this disease, it can be sprinkled with 0.3ppm~0.5ppm chlorine dioxide in the whole pool once a day for 2 ~ 3 days. The cage fish farmers washed the diseased fish with 0.7ppm~1ppm chlorine dioxide for 20 to 30 minutes, once a day for 3 days.

3. Red skin disease. The disease is caused by fish injuries and invaded by germs. Local or most of the body surface of the diseased fish bleeds, the scales fall off, the fin stem is congested, and the end of the fin decays in the shape of a broom, which is called "fin decay".

It can be sprinkled with 0.04ppm bromochlorohydantoin or 0.25 ppm superiodoquaternary amines in the whole pool. Once a day for 2 ~ 3 days.

4. Bacterial Gill rot. The pathogen is columnar flexor bacilli, which is generally caused by direct contact between fish and pathogens. The body color of the diseased fish is black, especially in the head; the Gill filaments are swollen, mucus is increased, and the end is defective; the skin on the inner surface of the operculum is congested and inflamed, and the middle part is often eroded into a round or irregular transparent window, commonly known as "skylight".

The diseased fish can be washed with the mixed solution of 0.8ppm copper sulfate and 1ppm bleaching powder for 15 ~ 20 minutes, or sprinkled with 0.15ppm benzalkonium bromide solution in the whole pool, once every other day, for 2 ~ 3 times.

(2) parasitic diseases

1. Fish bean disease. Because of the body surface of the parasitic fish, the parasitic place of the diseased fish is congested, inflamed, eroded, the mucus on the skin and Gill is increased, the Gill tissue cells are necrotic, and the diseased fish have difficulty breathing. Microscopic examination showed that a large number of bean worms were parasitized.

The treatment is that the fish can be washed for 20 to 30 minutes with 0.7ppm copper sulfate solution and copper sulfate ferrous sulfate (5 ∶ 2) mixture before stocking.

two。 Oblique tube disease. The pathogen is carp oblique tube worm, which is parasitic on the Gill and skin of freshwater fish. the disease has no special symptoms and is easy to occur in ponds with poor water quality and small area. it is one of the serious diseases in the late overwintering period in northern China.

0.3ppm~0.4ppm copper sulfate and potassium permanganate mixture (5 ∶ 2) or 0.7ppm copper sulfate solution alone can be used for whole pool sprinkling.

3. Melon disease. The pathogen is melon worm. Small dots of white bubbles can be seen on the skin, fin or fin of diseased fish, the scales fall off, the fin split and rot, swim slowly, float on the surface of the water, and sometimes cluster around the pond, and the fish constantly rub against other objects, or die in groups soon after jumping out of the water.

There are two treatments: 500g chilli powder and 100g dried ginger slices per mu, fried into 25kg potion, sprinkle in the whole pool, once a day for 2 days, or with 2ppm methylene blue in the whole pool, once every 2 days, 3 times in a row.

4. Anchor head disease, Zhonghua disease. The disease caused by parasite of Chinese mackerel can be sprinkled with 0.5ppm copper sulfate and 0.2ppm ferrous sulfate whole pool.

0.7ppm crystal trichlorfon can be sprinkled in the whole pool, once every 2 days, 3 times in a row. Or 15 kg ~ 20 kg of pine branches and leaves per mu, tied into 5 ~ 6 bundles, inserted and hung around the food farm or mashed, soaked and sprinkled in the whole pool.

5. Fish lice disease. Fish lice disease is easily prevalent in low temperature season, resulting in thin fish body, affecting growth, and can cause bacterial diseases.

For this kind of disease, 0.3ppm~0.5ppm crystal trichlorfon solution can be sprinkled all over the pond to prevent and cure the disease.