EFFECTS OF STRESS ON PLASMA-CORTISOL LEVELS AND BLOOD-VISCOSITY IN BLUE MAO MAO, SCORPIS-VIOLACEUS (HUTTON), A MARINE TELEOST

1. Freshly captured wild Scorpis violaceus had low plasma levels of cortisol (mean of 3.3 ng/ml). This rose to 30.4 ng/ml following 10 min of confinement stress. 2. Scorpis acclimated to laboratory conditions for up to 21 days after capture had higher mean plasma cortisol levels than freshly captured fish (19.6-38.3 ng/ml). Disturbance during serial netting from a stock tank resulted in a further increase to 73.9 ng/ml over 10-15 min. 3. Tank-acclimated fish exposed to 30-60 min of confinement stress showed a further increase in plasma cortisol to 276 ng/ml. Serial sampling of fish over 60 min of confinement gave similar plasma cortisol levels. 4. Hematocrits were not different in freshly captured, tank-acclimated or acutely stressed fish. Hermatocrits and hemoglobin concentrations were, however, lower in fish that were scrially sampled after 60 min. 5. Mean corpuscular hemoglobin concentration did not change in response to handling or confinement, indicating that erythrocyte swelling did not occur in response to stress. 6. Fish exposed to 60 min of confinement stress had lower blood viscosity at high shear rates than either tank-acclimated fish or fish exposed to 5 min of confinement. Only part of this effect could be explained in terms of reduction in hematocrit.