Fish Disease (Fish and Fisheries) by CBCS NOTE

 

Fish Diseases


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Fishes are aquatic organisms where they encounter various infectious agents such as bacteria, virus, fungi and sometimes parasitic organisms. Healthy fishes cultured in ideal aquatic parameters generally donot developed diseases. But sometimes those pathogens infact the fishes, thus affecting the productivity of cultured form ( the fish production)

 

   It is important to monitor the cultured fish in routin basis. Proper examination of fishes should be done if they developed.

        Unusual movement or swimming.

        Show abnormal growth.

        Complete or partial discoloration of body.

        Lost of scale.

        Rotting or infection in any part of body including fins.

        Damage or Discoloration of gills.

        Development of fill like covering in the skin.

        Excess slime secretion.

 

Fishes diseases can be divided on the basis of causative pathogen. The different types of fish Diseases are described below-

 

A) Bactericidal Disease:- 

Different types of bacteria can infect fishes & produced diseases.

a)      Tail and Fin Rot Disease:- This diseases are caused by

Pathogen:-Aeromonas, Pseudomonads, Mycobacterium and vibrio species (spp)

Symptom and Damage:- Initial damage in the fin or tail occurs due to mechanical reasons where the bacteria infect a whitish line or spot developes.

b)      Droapsy:- It is caused by

Pathogen:- Aeromonas punctata & Viral agent.

Symptom and Damage:- Accumulation of liquid occurs in the belly of the fish, liver and kidney are affected at later period. Ulceration of skin and lose of Scale may occur.

c)      Eye Disease:-

Pathogen:- Aeromonas sp.

Symptom & Damage:- Initially the cornea of the eye become reddish which turns opaque gradually. The eye ball also degenerate.

d)      Columneris Disease:-

Pathogen:- Flexibacter columneris.

Symptom & Damage:- Discoloration of body occurs followed by mile ulceration.

e)      Ulcer Disease:-

Pathogen:- Haemophillus piscicum.

Symptom & Damage:- Initially small lesion developes followed by formation of open ulcer. Secondary fungal infection may occur.

f)       Furunculosis:-

Pathogen:- Aeromonas salmonicidea.

Symptom & Damage:- Formation of boil containing blood & pus seen under the skin.

g)      Gill Rot Disease:-

Pathogen:- Flexibacter columneris, Mixi coccus.

Symptom & Damage:- Necrosis occurs in the gill filament where mucus & debrish accumulate.

h)      Vibriosis:-

Pathogen:- Vibrio spp.

Symptom & Damage:- Darkening of body, ulceration and abdominal droapsy.

 

B. Fungal Disease:-

 

Various aquatic fungi are capable of infecting fish species. Usually mechanical damage or ulcer produced due to bacterial infection increases the chances of fungal disease.

A)    Water Moule Disease or Saprolegniasis:-

Pathogen:- Saprolegnia, Achlya.

Symptom & Damage:- At first the fungi developed as a thin grayish or whitish layer on the wounded part of the body. The hypi of the fungi inved the inner tissue as time passes or infection increases. Water body rich in organic substance increases the chances of Saprolegniasis in fishes.

B)     Branchiomycosis:-

Pathogen:- Branchiomyces.

Symptom & Damage:- Decaying of gill occurs resulting haemorage, slim secretion increases, eye & body colour become pale.

 

 


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