Non-infectious diseases

Asphyxiation:

• Occurs due to the low dissolved oxygen content of water.
• Occurs when D/O level is below 1 mg/L.

Signs of low DO in fishpond

• Fish come to the water’s surface and gulp air very frequently.
• Fish aggregate in water inlet.
• Mouth wide open, gill opercula raised and gill spread wide apart.
• Mortality of fish in the morning

Control measures

• Using aerators
• Thinning out the fishes
• Supply cool water
• Liming the pond @ 500 kg/ha.
• Use chemicals like KMnO₄ @ 1-2 ppm