diseases in biofloc fish farming

Diseases and prevention in Biofloc fish farming

It is difficult to avoid fish diseases completely, it is better to try to prevent it. 

   

 Note: part is only to give you a general idea about the common diseases. no treatment should be tried on the basis of this chapter. Experts should be consulted before trying any treatment. 

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Understand the Causes of diseases first.

These are the main three causes of disease:

·         Improper feeding.

Be careful with fish feed. Lake of nutrition in feed can make them more vulnerable to disease. Also, Toxic factors in artificial food, any kind of unsuitable chemicals, fungus in stored foods, pesticides can also cause damage.

·         Stress due to hard handling.

Most of the damaged occur to the seed is due to the Rough handling when harvesting or in transportation. Which could damage skin and can grow to fungal decease if not take care of on urgent basis. overcrowding in storage or transport can also cause same damage.

·         Toxicity in water

Example of toxic water. Unsuitable water temperature, lack of dissolved oxygen, presence of toxic gases such as ammonia or hydrogen sulphide  pollution of the water due to agricultural or industrial chemicals, sewage water.

·         Germs Attack.

Get to know a few names related to fish diseases.

Saprolegniasis

Branchiomycosis

Ichthyophonus

The three most common fungal diseases. (Fungi are a group of organisms called heterotrophs. )

Fungi usually attack on the following conditions

If fish are stressed by disease, 

Poor environmental conditions, 

Receive poor nutrition, 

Injury

These factors weaken the fish or damage its tissue makes it vulnerable to infection.

SAPROLEGNIASIS

Attacks an existing injury and on poor water quality which could be due to ..

low water circulation

low dissolved oxygen

or high ammonia

high organic loads

presence of dead eggs

How will you recognize Saprolegniasis 

It can be observed in the form of fluffy tufts of cotton-like material colored white to shades of grey and brown on skin, fins, gills, or eyes of fish.If seen in microscope Saprolegnia appears like branching trees called hyphae. With infection fish usually becomes lethargic and less responsive to external.

Management and Control

Proper sanitation should be done. Common treatments include potassium permanganate. Caution should be taken as overtreatment can further damage fish tissue. 

BRANCHIOMYCOSIS

Commonly known as "Gill Rot" . High mortalities are often associated with this infection. (It is caused by the fungi Branchiomyces sanguinis (carps) and Branchiomyces demigrans (Pike and Tench). 

Main causes:

environmental stress

low pH  

low dissolved oxygen

high algal bloom 

unsuitable temperatures 

The main sources are fungal spores carried in the water and detritus on pond bottoms.

Disease Signs

Gills appear striated or marbled with the pale areas.

 Fish may appear lethargic.

Fish may be seen gulping air at the water surface.

 Gills need to be examined under a microscope for verification of the disease. 

Management and Control

Prevention is the best control for Branchiomycosis. Create environment unsuitable for fungi growth. Great precaution must be taken to prevent movement of the disease to non infected areas. All tanks must be disinfected, dried and treated with quicklime (calcium oxide). Dead fish should be buried. Formalin and copper sulphate is used to help stop mortalities.

ICTHYOPHONUS DISEASE

Caused by the fungus, Icthyophonus hoferi. It grows in cool temperatures (36° to 68°F). 

Disease Signs

Initially fish will not show any external sign. But in extreme cases, Some fish may show the curvature of the spine and curious swinging movements. Internally, the organs may be swollen with white to grey-white sores.

Management and Control

Prevention is the only control. Infected fish will carry the infection for life. To avoid the introduction of infective spores, never feed raw fish or raw fish products to cultured fish. Remove and destroy any fish with the disease. The complete disinfection of tanks is encouraged.