Fish health management

The best cure for any disease is prevention”

Fish health is influenced by three factors: environment, stress and pathogens (diseases). To have healthy fish you will need to have enough good food available, enough oxygen in the pond, protect them from predators, avoid too high stocking densities and handle fish well.

Make sure you get feeds and fingerlings from a reliable source, keep wild fish out of your farm and always disinfect your pond with lime to kill anything that could carry diseases.

Health management is more difficult and needs some experience. We thus strongly recommend asking an expert when abnormalities, signs of pathogens or parasites, are observed!

Common sources of stress for fish include:

        1.Poor nutrition

        2.Poor environmental conditions

        3.Overcrowding in ponds

        4.Rough handling of fish by farm workers

Symptoms of fish diseases

Diseases can be observed through changes in the fish appearance, behaviour and at an advanced stage: death.

Through observation you can already see if there is a potential disease/parasite popping up in your fishpond by looking out for any of the followings signs:

        1.Fish jumping out of the water

        2.Parasites on the scales/skin of the fish (might need a magnifying glass or microscope)

        3.Many fish “gulping air” at the water surface

        4.Large numbers of fish crowding around an inlet of freshwater

        5.Loss of appetite by fish

        6.Individual fish swimming erratically and apart from the rest

        7.Individual fish of unusual colouration—often very dark in appearance

        8.Individual fish swimming in circles (“whirling”)

        9.Retarded growth

        10.Distended stomach

        11.Fish flipping on water surface, scraping or jumping

        12.External parasites visible on the fins, body, or gills of fish; parasites (worms) visible on/in internal organs

        13.Excess mucus on skin

        14.Cotton- or wool-like growths (fungus) on the skin surfaces

        15.Peeling skin, ulcers, lesions, and erosion of fins.

        16.Fish deaths increasing over time

         17.Make sure your farm workers are trained to look out for these symptoms can record and report them to the farm manager/owner.

Disease prevention

        1.Proper fish handling to avoid abrasion, which causes removal of scales and slime.

        2.Screen at the inlets and stocking disease free fish or fingerlings.

        3.This is done after draining the pond.

        4.Use uncontaminated water supply.

        5.Proper aeration by addition of fresh water at the inlet.

        6.Stock fish at recommended density, control overcrowding due to overpopulation by stocking catfish.

        7.Prevent accumulation of organic matter, which takes up oxygen during decomposition.

Waterborne human diseases

Malaria

Malaria is caused by mosquitoes which breed in stagnant water.To prevent mosquitoes breeding construct regular pond i.e. rectangular with smooth banks to avoid creation of spaces where water would stagnate and fish cannot get to the larvae.

Bilharzia

Spread by water snails. Make sure you NEVER pee directly into the water to avoid spreading the disease.

Fish diseases

In general: tilapia and catfish tolerate adverse water quality and other stressors to a certain extent. Because stress and environmental quality play such important roles in the disease process, tilapia is labeled as being very "disease resistant".

Examples of parasite infestations

Examples of extreme or advanced cases of disease or parasite infestations include:

        1.White lesions on the head, back, and gills

        2.Hemorrhagic ulcers on body or on internal organs

        3.Deep ulcers extending into muscles

        4.Internal bleeding and kidney damage or anemia

        5.Sloughing away of gills and excessive slime

Preventing diseases

The best way to avoid diseases is to prevent them from happening. Most important is good hygiene on the farm and for anything entering the farm.

The following should be taken into consideration:

        1.Maintain good personal hygiene (washing hands and foot baths) also for visitors

        2.If there is one pond with a disease, disinfect any tool used there before using it in any other pond

        3.Remove dead fish immediately and fish showing symptoms of disease (rather kill 10 fish than losing 1,000)

        4.Reduce stocking density to reduce stress

        5.Lower or stop feeding (can reduce mortality)

        6.Treat the disease with antibiotics or salt, if prescribed

        7.In case of serious infection (mass mortality), harvest all and sell immediately, drain your pond, clean and disinfect thoroughly and start         afresh.

If you get caught with parasites, you can kill them pretty easily!

        1.Change the salinity of the water to 6 parts per thousand, using non-iodized salt as this will wipe out the parasites very quickly.

        2.EXAMPLE: 300 m 2 pond , 1m water depth: (300x1000)x0.006= 1.8 kg

        3.Individual tilapia with parasites can be treated by placing them in a tank of water containing 6 ppt of non-iodized salt for a few hours.

        4.Adding salt to a measurement of 6 parts per thousand is roughly one tablespoon of salt per liter of water; never expose tilapia to water         containing salt levels above 18 parts per thousand (e.g. 18 g per liter water).

        5.If you have individual fish to be treated you can also use formalin.

Symptom Pathogen Prevention
1. Cottony grey-white or brown patches on the skin Fungus Good handling Avoid handling fish in cold water. Low organic matter in water
2. Black spots -Yellowish cysts on gills Trematodes Control snails and discourage birds. Remove infected fish.
3. Loss of appetite. -Fin and tail rot. Pale gills -Fluid in abdomen Bacteria Improved water quality
4. Round worm in spiral shape near gills Nematode (Contracaecum) Not really a problem for fish health but leads to consumer dissatisfaction
5. Fish try to scrap their bodies on hard surfaces (flashing) Parasitic protozoan Dip in salt, Potassium Permanganate or formalin. Keep water temperature near optimum range for that species of fish.