Author: Chen Qi, Technician of Sihai Fishing Shop, Jiangdi Road, Wuxue City, Hubei Province (Beijing Yumeikang Biotechnology Co., Ltd.); Cheng Huihui, College of Fisheries, Huazhong Agricultural University
Fish parasites are widely available, but most are conditionally pathogenic. Some parasites are specific and can only parasitize on specific hosts (fish), but a fish can be parasitized by multiple parasites. After being parasitized by parasites, fish often cause a decrease in their appetite, difficulty breathing, inflammation and anemia in the body, and lead to death. For parasite control, the main thing is to cut off the source of infection, maintain a good water quality substrate, improve the fish's own immunity and resistance, and do a good job in disinfection at various stages. Remember, do not wait until the parasitic disease is serious before starting to kill insects, because insecticide is not only risky and has a great impact on the growth and breeding of fish, some insecticides are also easy to kill some of the plankton in the water caused by water imbalance and make the water quality worse, so for parasitic diseases to focus on prevention, to water care.
1 wheel worm
Rotifers are in the genus Ciliate Phylum, Order Phylloscopus, Family Rotiferidae. The side of the insect body is felt-like, the reverse side is disc-shaped, and when it moves, it is like a wheel turning, the raised side is the front or mouth surface, and the relatively recessed side is the back or reverse mouth surface. The wheelworm attaches to the gill or skin of the fish with an attachment disc and slides back and forth, sometimes leaving the host to swim freely in the water. When swimming, it is generally turned like a wheel with a back mouth facing forward, so it is called a wheel worm. Wheelworm can be detected all year round, endemic in April to July, but summer and autumn as the peak season, its suitable water temperature of 20-28 ° C, often parasitic fish on the gills and fins, fry can appear "white head white mouth" or "running horse" (swimming around) symptoms. The number of wheelworms on healthy fish living in a good environment is very small, even if they exist; but in poor environments, such as small water bodies, excessive stocking density, etc., or when fish bodies are injured and other diseases occur, and the body is weak, wheelworms often multiply in large numbers and become diseases. Seeing a small number of insects under the microscope does not have much effect and cannot be blindly killed, because it is common for small amounts of insects to attach to the gills. On microscopy, more than 10 × under the microscopic field of view can confirm the onset of the disease.
Prevention: Pay attention to inspection before releasing seedlings, the stocking density should not be too large, reduce the mechanical damage of the fish body, improve the immunity of the fish body, and maintain good water quality.
Treatment: Copper sulfate and ferrous sulfate combined (5:2) are sprinkled in the whole pool, or the formalin is sprinkled in the whole pool. There are special drugs on the market to kill wheel worms, and mandarin fish should be cautious in killing wheel worms.
2 Gill mold
Gill mold invades the gills of the fish body and causes the onset of fish disease, which is gill mold disease. Gill mold disease is a common disease of fish, this disease often occurs in water bodies with high organic matter content and poor water quality, often occurs in May to October, June to July is the peak of the incidence, the incidence rate can reach 70%-80%, the mortality rate can reach 90%, the harm is serious.
Prevention: Keep the water fresh frequently to prevent the deterioration of water quality, and regularly sprinkle 25ppm quicklime throughout the whole pool.
Treatment: sprinkled with mold net or poultry with erythromycin full name.
3 small melon worms
The small melon worm belongs to the protozoa phylum, ciliate, notch family, and small melon worm genus, mainly parasitic in the skin, fins, gills, head, mouth and eyes of fish, forming a small white dot-like sac, which is visible to the naked eye. In severe cases, small white spots can be seen all over the body of the fish, so it is called white spot disease. Under the microscope, the small melon worms are spherical trophozoites and the nuclei are horseshoe-shaped.
Prevention: Regularly clean and disinfect cages, daily feeding should strengthen nutrition, improve the resistance of fish.
Treatment: Use betel nut medicine packs hanging around the cage for treatment, wash the cage before hanging bags, and use the drug treatment continuously according to the course of treatment.
4 Larvae
Twigs are protists and are called twigs because their growth forms resemble dendritic. The individual form is bell-shaped, the stalk is straight and thick, transparent and muscleless, and the group stalk does not contract. Mycoccystium generally grows solid in the bacterial gel group, relies on the cilia on the bell body to prey on food, and has elasticity, using bacteria as food sources, especially preferring to eat E. coli, Pseudomonas and so on. Mycoidium and monotococcystes, polycontozoans and bellworms, once epiphytic on the surface, appendages, eyes and gills of shrimp and crabs, cause shrimp and crab disease, that is, ciliate disease.
Prevention: Strict insecticidal disinfection of aquaculture water, reasonable feeding of feed and enhancement of fish body immune resistance.
Treatment: Mix formalin (concentration 10mg/L) and hyacinth (Shanxi Yuncheng Jinlin Biotechnology Co., Ltd., concentration 10mg/L0.075g/m3) to mix the whole tank and evenly sprinkle.
5 solitary shrunken worms
Monotochophyllum is a single-celled protozoa, belonging to the bell worm class, with the characteristics of small size and complex structure, which can ingest organic matter into the cell-eating organs to decompose, and has the ability to purify sewage, so it has important applications in sewage treatment. Monotochoccals and tired insects, polycarpies and bellworms, once attached to the surface, appendages, eyes and gills of shrimp and crabs, thus causing the onset of shrimp and crab disease, that is, ciliate disease.
Prevention: Sprinkle quicklime once every half a month to keep the pool fat, live and cool for a long time.
Treatment: Whole tank sprinkled with 1 ppm zinc sulfate or 1 ppm chiroathine net.
6 Ringworms
Ringworms are parasites of the genus Helminths and are a common parasite that is mainly transmitted by eggs and larvae. It is endemic in late spring and early summer, and the suitable temperature is 20-25 ° C. In large amounts of parasitism, the gill filament mucus of the diseased fish increases, and the gill filament is swollen, pale, and anemia. The gills of the sick fish are open, have difficulty breathing, swim slowly and die. The main hazards are silver carp, bighead carp and grass carp, which are common when inspecting grass carp in the market.
Prevention: Soak with potassium permanganate for ten minutes before releasing seedlings, the stocking density is moderate, and the water quality is maintained.
Treatment: Sprinkle crystal enemy worms throughout the pool, or use the special medicine on the market to kill ringworms.
7 Myxosporidium
Myxosporidium refers to a large class of protozoa of the myxosporid class, found in China's freshwater fish species have more than 300 species, almost every fish has parasitism, can invade the fish body and foreign tissues and organs, for the common parasites of fish. Myxosporidium parasitizes, multiplies and forms sacs in fish, causing damage to parasitic tissues and organs, destroying their normal function, causing corresponding symptoms, affecting the growth and development of fish, and even death. Myxosporidium reproduces only with water earthworms as an intermediate host. Mature spores are difficult to kill and are prone to drug resistance. Today's myxosporidium has no specific drug that can kill it completely.
Prevention: Completely remove water earthworms from the water.
Treatment: external use of copper sulfate to kill, internal administration of chlorobenzanide hydrochloride, dikopramide, artemisinin, etc.