Effects of Acute Drop of Ambient Temperature on Respiration and Blood Circulation of Porgy

Abstract

Adjustments in respiration and blood circulation of a porgy Pagrus major exposed to acute drop of temperature were investigated. Water temperature was lowered from the acclimated level of 21°C to the test level of 16°C at the rate of 0.13°C-min^-1, kept at 16°C for 3hours, and returned to 21°C at the same rate. In the period of lowered temperature, oxygen consumption was reduced to 60% of the precooling level. Respiratory frequency, stroke volume of gill ventilation, and minute volume of gill ventilation decreased to 73%, 41%, and 57% of the pre-cooling level. Oxygen utilization at the gills, partial pressure and concentration of oxygen, hematocrit value, hemoglobin concentration of the arterial blood, and oxygen concentration in the mixed venous blood did not show any significant change. Arterial pH elevated. Heart rate decreased, stroke volume of cardiac output increased, and minute volume of cardiac output did not significantly change. Oxygen utilization at the tissues did not change. All the parameters showed the pre-cooling level when water temperature was returned to 21°C. From these results, lowering temperature by 5°C is considered to be an effective and safe way for successful transportation of live fish.