Potential impact of metabolic acidosis on the fixed-acid Bohr effect in snapper (Pagrus auratus) following angling stress

Oxygen equilibrium data were obtained for intact erythrocytes from Pagrus auratus and the pH-dependence of the fixed-acid Bohr and Root effects described. Indicators of aerobic–anaerobic poise were then measured following a period of strenuous exercise induced by angling capture. Haematological indices and plasma metabolites were evaluated with respect to their potential impact on the blood oxygen transport mechanism. An increase in post-capture haemoglobin content, blood lactate, and glucose were observed. The fall in caudal venous pH from 7.53 to 7.41, reflecting the acid–base status of blood draining the working tail musculature, remained within the operational zone of the maximal fixed-acid Bohr effect (Φ7.4–7.8 = − 0.95), but above the critical pH at which the Root effect suppresses oxygen transport capacity. These stress-induced changes reflect a strategy of optimal O2 unloading to tissues with the Root effect unlikely to be expressed in the swimming vasculature.