types of fish diseases : how to prevent and what causes

types of fish diseases

fish diseases, according to wikipedia, like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.

With the arrival of spring, the temperature starts to rise gradually and the water temperature keeps rising, which also accelerates the growth and reproduction of harmful bacteria in fish ponds. As the temperature gets higher and higher, summer comes, the water temperature is suitable for fish growth and fish food is flourishing in summer, which is the prime season for fish growth.

However, due to the high summer temperatures, the weakness of fish after overwintering, the vigorous metabolism of fish, the massive accumulation of feces, and the large amount of residual bait deposited on the bottom of the pond, resulting in the deterioration of pond water quality and substrate ( you can check our post about How To Improve Pond Water Quality ), This has led to the frequent occurrence of various types of fish diseases, which can easily cause water mold, erysipelas, bile duct disease, trichinosis, etc., and directly affect the economic benefits. The following are some common types of fish diseases.

Types Of Fish Diseases

1. water mold disease

Water mold disease is an infectious disease caused by damage to the surface of freshwater fish caused by factors such as straining and frostbite. The causative agent is widely present in the water column and is an opportunistic pathogen. After invading the fish body, the water mold will reproduce sexually and form white flocculent material, which adheres to the surface of the fish body. Fish are irritable, appetite decreases, cannot move normally, immunity gradually decreases, and other infectious diseases are easily induced. If the treatment is not timely, the fish will easily die due to weakness.

2. red skin disease

The occurrence and prevalence of erysipelas is very similar to that of water molds. It is usually caused by factors such as net pulling and frostbite, which cause damage to the surface of the fish and infection with Pseudomonas fluorescens. Pseudomonas fluorescens is also an opportunistic pathogen that is widely present in the water column. When there is no damage to the surface of the fish, infection does not usually occur.

If there is visible damage on the surface of the fish, pathogenic bacteria will enter and multiply through the damaged area and produce clinical symptoms. After the fish are infected with the pathogen, the body surface will be severely congested and inflamed, the scales will fall off, and the fin tissue will be severely damaged, forming a “broom” shape. When the disease is severe, a large number of water molds will be parasitized in the sick fish where the scales fall off and the fins rot, leading to more severe clinical symptoms and higher mortality. The disease mainly affects grass carp, herring, carp and crucian carp.

Prevention Of Fish Diseases

3. vertical scale disease

The main manifestation of vertical scale disease is that the fish scales open outward and fall off with light pressure, and there is liquid overflow. At the later stage, the fish abdomen swells, loses balance and dies quickly. It is generally prevalent in the season of low water temperature or when the water temperature changes in a short period of time.

4. oblique tubeworm disease

The main symptom of oblique tubeworm disease is that the diseased fish begin to secrete large amounts of mucus, forming a white mucus layer on the body surface. Once the water temperature conditions are suitable, chinstrap worms will multiply and cause mass mortality within 2-3 days.

5. Bacterial putrefaction

Inflammation and congestion of part or most of the body surface of the diseased fish; descaling; congestion of the fin bases, vesicles of the fin tips, and destruction of the tissue between the fin bars; erythema often appearing on the zygomatic bone and upper and lower foreheads, with the zygomatic bone sometimes decaying to expose the zygomatic bone. The disease mostly occurs in late spring and early summer. Diseased fish swim slowly, often alone on the water surface, and die quickly.

How To Prevent Fish Diseases

what causes of fish diseases

1. fish farmers to pursue economic benefits to increase the density of breeding, which will increase the probability of disease. With the increase in farming density, the amount of baiting increases, a large amount of residual bait and manure accumulates in the bottom of the pond, pollution exceeds the pond’s self-purification capacity, resulting in unstable and deteriorating water quality The bottom of the pond is in a state of oxygen deficiency, resulting in an increase in nitrite, ammonia, hydrogen sulfide and other toxic and harmful substances, making it easier to break out various fish diseases.

2. Moldy, spoiled or nutritionally incomplete feed and the frequent use of antibiotics are also important causes of fish illness in the summer. Frequent use of antibiotics and feeding spoiled and moldy feeds can easily cause malnutrition, pale liver, swollen gall bladder and discoloration of lesioned parts, resulting in poor fish quality, reduced resistance and susceptibility to various diseases.

3. Poor water quality, increased water pollution, pond water hypoxia, ammonia, nitrite, hydrogen sulfide and other toxic and harmful substances increased, resulting in increased fish diseases and increased breeding costs.

4. As a result of split-pond stocking, the fish body is damaged, opening the way for bacterial invasion. Such fish diseases mainly include water mold, vertical scale disease and gill rot, as well as red skin disease.

5. In spring, the fish are weaker after overwintering. This is the time when some parasites multiply and invade the cultured fish. One way is to invade the gills of the fish, causing inflammation and decay of the gill filaments.

What Causes Of Fish Diseases

how to prevent fish diseases

1. The amount of feeding can be flexibly controlled according to the weather, water quality and fish eating conditions. The feed insists on using the full-price compound feed produced by regular manufacturers. It is required to use fixed-point baiting, build a baiting table and observe the fish eating situation in time.

2. Pay attention to water quality adjustment, regularly replenish new water, generally once every 7 to 10 days. Regularly turn on the aerator to agitate the sludge at the bottom of the pond to promote sludge decomposition. Stirring is best at noon on sunny days. Stirring should be stopped when the weather is hot and the air pressure is low.

3. When transporting fish fry out of the pond, mechanical damage should be avoided as much as possible. When selecting and purchasing fry, choose fry that are robust, active and of neat specifications. Disinfection should be carried out before entering the pond. Generally, physiological saline or potassium permanganate solution should be used to disinfect before entering the pool.

4. Clean the bottom of fish ponds regularly, every 10 to 15 days, depending on the condition of the pond. Maintain a good fish pond environment that does not provide an environment for parasites to live in. Effectively prevents parasites from multiplying.

Treatment Of Fish Diseases

prevention and treatment of fish diseases

1. Saprolegnia Diseases

prevention of fish diseases

Thorough cleaning of the pond with quicklime can reduce the incidence of this disease. Take care not to injure the fish when fishing and stocking, and stocking density should be reasonable. Fish species transported over long distances should be disinfected with 2% to 3% brine or disinfectant before stocking.

treatment of fish diseases

Choose to spray the disinfectant on a sunny day. If fish are poorly energized, spray disinfectant 2 hours before disinfection. In the afternoon, soak the disinfectant solution in hot water above 70℃ for 30 minutes and sprinkle it evenly over the whole pool. Sprinkle 15 pounds of salt and 15 pounds of baking soda per mu, just once.

2. red skin disease

prevention of fish diseases

During the catching, transportation and stocking of fry, damage to the fish should be avoided as much as possible and the surface damage should be inspected before stocking. You can choose to completely soak the fish with an iodinated disinfectant for 30 minutes before placing them in the fry. When the fish in the pond are sick, you can choose to spray the entire pond with an iodinated disinfectant.

treatment of fish diseases

Sprinkle lime 10-15kg/mu in the whole tank; Chlorine dioxide powder 0.25kg/mu, once every other day, 3-4 times in a row. The mixture is fed with 100lbs of mixture per bag or evenly sprinkled into the whole tank, with a water depth of 3-5μm per bag, once a day for 2-3 days, with dosage adjusted as appropriate .

3. vertical scale disease

prevention of fish diseases

Avoid injuring fish during stocking in separate ponds and kill parasites on fish in a timely manner. Spray the whole pool with chlorine-based disinfectant to prevent it from happening. Also, disinfect with 3-5% brine soaking before releasing the fry.

treatment of fish diseases

Sprinkle bleaching powder 1.5-2 kg / mu, once every other day, 3-4 times in a row. Feed with 100 kg of mixture, or evenly sprinkle the whole tank into the whole tank, watering depth of 3-5μm per bag, once a day, for 2-3 days.

4. oblique tubeworm disease

prevention of fish diseases

Clean the pond with quicklime to kill pathogens that remain on the bottom. Soak fry in 2% brine for 20 minutes before stocking.

treatment of fish diseases

Use 200 kg of ingredients per bag of Roundup, 2 times a day for 5-7 days. Or sprinkle the whole pool evenly with Roundup, sprinkle 3-5μm water depth per bag, once a day for 2-3 days, and adjust the dosage as appropriate.

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