The regulation of hypercapnic acidosis in two Salmonids, the freshwater trout (Salmo gairdneri) and the seawater salmon (Onchorynchus kisutch)

A comparison was made between the ability of a freshwater teleost (Salmo gairdneri) and a seawater teleost (Onchorynchus kisutch) to regulate hypercapnic acidosis (1% CO2). Although both species regulated blood pH in the same manner, by accumulating plasma bicarbonate, it was observed that O. kisutch regulated the acid‐base disturbance much more rapidly and efficiently than S. gairdneri. The differences in regulatory efficiency are not due to fundamental differences in kidney or gill function. It is speculated that the marine fish (O. kisutch) regulates hypercapnic acidosis more effectively than the freshwater fish (S. gairdneri) due to greater buffering capacity of the external medium.