Blood Respiratory Properties of Rainbow Trout (Salmo Gairdneri) Kept in Water Of High CO2 Tension

Abstract

1. Blood O2 transport and acid-base balance were studied at 20°C in rainbow trout (Salmo gairdneri) which had been kept in water of high CO₂ content (15 mmHg) for at least a week. Also the blood gas chemistry of fish rapidly entering or leaving the hypercapnic environment was studied. 2. Fish entering high CO₂ water suffered a sharp decrease in blood pH which significantly reduced O₂ transport by the blood, but after a few hours considerable compensation was achieved. 3. After at least a week in high CO₂ water, trout showed elevated plasma bicarbonate and PCO₂ levels, and a decrease in plasma chloride, while pH was about 0 - 1 pH unit below the level for control fish. Oxygen transport by the blood was marginally reduced. 4. Hypercapnic fish rapidly entering fresh water showed a sharp increase in blood pH and a decrease in blood PO₂. These parameters regained normal values after a few hours but plasma bicarbonate and chloride levels took much longer to regain control concentrations. 5. Acid-base balance in hypercapnic fish is discussed with particular reference to the role of the branchial ion exchanges.