Fish Diseases and Management

2.1.5 General Adaptation Syndrome (GAS)

The changes which occur in response to environmental stress are termed as General Adaptation Syndrome,  by which  animal tries to adopt to its original condition. 

These adaptations normally occur in three phases.

i)    Alarm reaction

ii)   Stage of resistance

iii)  Stage of exhaustion

i) Alarm reaction

            This is due to physical response of the animal to stressor i.e animal escape due to the external stimuli eg:handling nething change in  physiology if D.O reduces significantly and the animal comes to the surface, chemical change i.e. change in pH or dissolved oxygen or range amount of ammonia.

ii) Stage of resistance

            During this period, adaptation to achieve homeosatasis under the changed circumstances takes place.

iii) Stage of exhaustion

            When the animal is unable to achieve homeostasis i.e. resistance / change.

the animal gets exhausted. If it reaches this stage, it may lead to disease. 

            When an animal course these three stages and comes back to the normal condition, the animal does not have disease.