There are literally hundreds of afflictions that can effect the health of farm fish. The most common maladies seen in home aquaculture production are usually either bacterial, parasitic, or viral diseases in origin. Fungal infections are also sometimes seen, and occasionally physical ailments.
Luckily, most fish ailments are easily diagnosed and can be treated with success. Here is the most common of these afflictions. How to prevent fish disease has methods you can take to reduce the possibility of disease and help to keep disease from spreading if it should occur.
Common Fish Diseases & Symptoms in Freshwater Cultured Fish
1. Bacterial Disease
Bacterial diseases are caused by the infection of bacteria in fish body.
Bacterial hemorrhagic disease: This disease is most likely to harm grass carp. In early stage of illness, fish will show signs of bleeding, which usually occurs in the fin base, gill cover, mouth and lower jaw, if it continues to develop the fish body will have bleeding, the abdomen will be expanding, and red spots will appear at liver and kidney.
Gill rot disease: The disease is most likely to harm grass carp and common carp. In early stage of illness, the fish will loss of appetite, the head will go black with increased mucus, if it continues to develop, the gill part will appear the wax yellow and mud gray spot.
2. Parasitic disease
The most common parasitic diseases is Myxospore disease, Dactylogyrusis, Trichodiniasis, Lernaeosis, etc. Common carp were the most susceptible to the Myxospore disease, the carp and Bighead are most susceptible to the Dactylogyrusis, wheel worm is the main invasion of common carp, it is not easy to find in the early stage, and the biggest victims of the Lernaeosis is grass carp, especially the most popular in the summer.
3. Viral diseases
Virus disease is a disease caused by a variety of viruses that invade the body of a fish. Hemorrhage of grass carp is the most serious disease in breeding stage, virus will invade the gills of fish, around the eyes, head, jaw and other parts, and the whole fish is dark black. This disease is more likely to occur in small grass carp, once suffering from the disease, the mortality rate is very high, can reach 80%, and will die in 3 – 2 hours.
Viral hemorrhagic septicemia virus (VHSV) is a rhabdovirus, could cause rainbow trout (Oncorhynchus mykiss) infection on the acute and sub acute, the mortality rate as high as 80%. Pathological features of the disease are necrosis of hematopoietic organs such as spleen, kidney and pancreas. Acute type of performance shows the exophthalmus, bleeding and rapid death; Chronic infection showed movement disorders, anemia and slow death. The disease is prone to outbreaks in the late winter and early spring, when water temperature is below 14oC. Pathogens could be diagnosed by isolating the viscera, blood or ascites of the diseased fish.
What Factors would Cause Fish Diseases
1. Natural factors
Effect of water temperature：Temperature of natural fresh water will change with the seasons change, but this change will cause a lot of fish sick and dying in large numbers, because some of the parasites that threaten the health of fish disappear or appear to be affected by temperature change, for example, early winter, late spring and early summer, the water temperature at this time is more suitable for the survival of Ichthyophthirius, August and September are hemorrhagic disease of grass carp in the epidemic period, early spring and late winter is saprolegniasis popular period.
The impact of dissolved oxygen: Dissolved oxygen is the content of oxygen in water, will have a very large impact on the survival of fish. If the oxygen content in the water is too low, the fish will be prone to rotten gill disease, if the oxygen content in the water is as low as 1mg/kg, then it will lead to a large number of fish deaths, of course, too high oxygen content will cause the fish suffering from gas disease.
The pH value of the water: pH in 8.5-7 is the most suitable for the growth of fish, that means neutral and weakly alkaline environment is more suitable for the survival of fish, if pH is less than 5 or higher than 9, it will lead to a large number of fish dead.
2. Water pollution
Now with the rapid development of township enterprises, leading to a lot of sewage into rivers and lakes, and these sewage is the cause of the fish disease, sewage contains a large number of heavy metals and a variety of micro-organisms, will pose a threat to the survival of fish.
Abnormal fishing: If the fishing method is improper, it will cause the disease and death of the fish, for example, careless operation will cause the fish to be injured, will give microbe an opportunity to cause fish ill. In addition, if the production density is too large, it will also lead to the death of fish sick.
3. Feeding fish with fish feed pellets of low nutritions
Good nutrition in animal production systems is essential to economically produce a healthy, high quality product. In fish farming, nutrition is critical because feed represents 40-50% of the production costs. Fish nutrition has advanced dramatically in recent years with the development of new, balanced commercial diets that promote optimal fish growth and health. When it comes to fish feed nutrition, we have to talk a little about fish feed formulation: the feed formulation is not immutable. In different fish growth stages, different formulation should be used to satisfy its nutrition demands! In our previous articles, we have summarized several quality formulations, such as Shrimp Feed Formulation and its Manufacturing Process, for your reference only!
The following is essential nutrient in fish feed.
Protein is an important nutrient for fish survival, is an important material composition of cells, tissues and organs of the body. Fish normal growth need to feed in a number of sufficient, easy to digest and absorb, a variety of amino acid ratio of the appropriate protein. When fish intake protein deficiency, it will cause slow growth, decreased body immunity, slow tissue regeneration, poor wound healing ability, easy to sick. Excessive protein intake, the protein that not digest and utility will be excreted in the form of nitrogen. It not only decreases the body of protein utilization efficiency, and increase the pressure of the water quality management, at the same time, it is easy to cause the occurrence of intestinal diseases. In the relative suitability of protein level, amino acid balance will not only enable fish to obtain rapid growth rate and enhance the immunity.
Fat, especially fatty acid, is an important regulator of the immune response of fish, adding essential fatty acids in daily diet can improve the humoral immunity and cellular immunity of animal body, can promote the production of cellular immune factors, it has an important effect on the proliferation of lymphocytes stimulated by mitosis, which can enhance the phagocytic ability of macrophages.
VC is the necessary nutrients for fish and shrimp to have normal growth and maintenance of normal physiological function, while many fish can not be synthesized, must be obtained from the diet. VE is also important nutrients for fish, its main function is to protect the fat soluble cell membranes and unsaturated fatty acids from oxidation. The appropriate amount of VE can be used to enhance immune, enhance the function of phagocytosis cells, enhance production of phagocytic cells. VA is required for fish to maintain the normal function of the immune system, high levels of VA in fish feed can can improve lymphocytes in vivo phagocytic ability, vitality of serum lysozyme and specific complement, which has an important effect on the fish immune function.
Mineral elements such as iron, selenium, copper, zinc and other elements are very important for disease resistance and immune response of fish and shrimp.
Except for the quality of fish feed pellets, Feeding Rate, Frequency, and Timing also influence the growth of farmed fish!
All in all, there are certain reasons and conditions, in the general case, the occurrence of fish diseases decided to pathogens, perception of fish body, and the environment.
Fish Disease Treatment Strategies
1.Treatment strategy of bacterial diseases
There are two kinds of bacterial diseases: bacterial hemorrhagic disease and bacterial Gill disease. Bacterial hemorrhagic disease is a common disease of freshwater fishes, in the early stage, mild bleeding symptoms will appear in both sides of the fish body and mouth, as well as the fin base and the upper and lower cheek, later it will find the bleeding in the fish body, some fish scales will appear erect phenomenon, fish belly will appear swollen phenomenon, this needs to be treated with drugs, can use the aerator to put chlorine such dags into water. Bacterial Gill disease, under normal circumstances, you can use Calcium lime to clear the fish pond, or add drag into fish feed.
2.Treatment strategies for parasitic diseases
For Ichthyophthirius disease, need to use special drag, and continuous to use 3 to 7 courses before they can completely eliminate. A mixture of pepper and ginger can also be poured into pond. Myxosporidiosis often occurrence in common carp, once get the disease, it will appear gray white cysts in gill, pectoral, ventral, caudal and other parts. In severe cases, tumor like cyst will appear in mine eyes, intestine and brain, can use Calcium lime or bleacher to clear the fish pond. For already sick fish, you can use the Junduke and iodine and other drag to cure.
3.Treatment strategies for viral diseases
In freshwater fish, grass carp is the most susceptible to viral hemorrhagic disease, once grass carp infected with viral hemorrhagic disease, its eyes, head and gill and other parts appear congestion, the whole body is dark black. For viral hemorrhagic disease, now it has not developed effective drugs, can only use lime and bleaching powder to disinfect fishpond and remove the pond sludge.
Fish Disease Preventive Measure & Control
Scientific stocking, raising the disease resistance of the fish body, control of the pathogen and the use of drugs and other measures.
Scientific stocking: the water should be adequate, clean, free from pollution, the physical and chemical characteristics of water should be suitable for fish habits. Therefore, water should be from the independent intake channels, fill the new water regularly, the water must not discharged into other ponds, to prevent the spread of fish diseases. A variety of fish polyculture can reduce the incidence of parasitic disease; dense stocking but not make the density too high can not only ensure the yield per unit area, but also prevent excessive contact with the fish from causing a highly contagious disease. Fish Feed should be qualitative, quantitative, positioning, timing, periodically check the fish season, eliminate weeds, bait, dead fish and parasite intermediate hosts, to prevent disease occurrence and spread. If you produce fish feed pellets yourself, please choose suitable feed formulation, and High Quality Fish Feed Machines.
Improving the disease resistance: Vaccine for fish, or immersing the fish body into vaccine liquid can make the fish body get immunity. Vaccine generally isolated from the diseased fish, pathogens was made after culture, inactivation and other processes. Sometimes grinding disease fish viscera, filter to the residue, inactivate filtrate. Through artificial selection or hybrid method to cultivate fish varieties with strong resistance to disease, it is a positive means of preventing fish diseases.
Control pathogen: Before stocking, farmers should drain the water, remove the bottom surface of the sun and remove the pool sludge, weeds etc., to eliminate pathogens and parasite oviposition sites. Can also sprinkle lime, bleaching powder, tea cake into fish pond for drug cleaning, disinfect the water weeds, manure, fish feed, farming tools and other places before use them. In order to prevent the spread of the international spread of pathogens, the import and export of fish to be quarantine. Regulations of the people’s Republic of China on import and export of animal and plant quarantine and Interim Provisions on Quarantine of freshwater fish at the port Determined scope, object, method and processing method of quarantine, any of the pathogens causing serious harm to the fish but lack of effective methods of prevention and control, such as the infectious pancreatic necrosis virus from salmon and trout of, the Myxosoma cerebralis could cause rotation disease, etc. are listed as the main object of quarantine.
Administration of drugs: For the prevention and treatment of fish diseases are the main types of halogen(Bleaching powder, sodium chloride, iodine,etc.), Heavy metal salt(copper sulfate and ferrous sulfate, cupric chloride, potassium dichromate, etc.), sulfonamides (sulfadiazine, sulfathiazole, sulfonamides, etc.), furan (nitrofurazone, furan ketones, disable fishery drugs), organic phosphorus insecticide trichlorfon, etc.), antibiotics (penicillin, streptomycin, chloramphenicol, chlortetracycline, oxytetracycline, erythromycin, etc.), Chinese herbal medicine (Sapium sebiferum, rhubarb, garlic, Euphorbia humifusa, iron, etc.), As well as other bactericidal effects(Malachite green and methylene blue dye, lime, sulfur, borax, Potassium Permanganate etc.).
