Anaesthetics

Abstract

The following stages of anaesthesia in fish are generally recognized:

• 1. Light sedation — Slight loss of reactivity to external stimuli, equilibrium normal:

• 2. Deep sedation — Total loss of reactivity to external stimuli except strong pressure; slight increase in opercular ventilation rate; equilibrium normal;

• 3. Partial loss of equilibrium — Partial loss of muscle tone, erratic swimming; reaction only to strong tactile and vibrational stimuli;

• 4. Total loss of equilibrium — Total loss of muscle tone and equilibrium; rapid opercular ventilation (slow with some agents); reaction only to deep pressure stimuli;

• 5. Loss of reflex reactivity — Total loss of reactivity; opercular movements very shallow, heart rate very slow;

• 6. Medullary collapse — Opercular movements cease immediately after gasping, followed by cardiac arrest.