... whole-animal air exposure. These hypercapnic challenges caused an immediate reduction in arterial pH, followed by progressive compensation through a marked elevation of plasma HCO 3 − over the course of 72 h. There was no appreciable rise in urinary acid excretion in fish exposed to hypercapnia in water...

...Richard F. Burton SUMMARY Mean values of normal arterial pH in different species of fish, amphibians and reptiles at 15 and 25°C, taken from the literature, are negatively correlated with arterial P CO 2 and plasma [Na + ]. At either temperature, the data accord with the hypothesis...