where VR represents the constant water flow through the
respirometer (L h1), a denotes the solubility coefficient for
O2 in water (mlO2 L1mmHg1) and Wt the bodymass (kg).
Both fR and V˙ O2 were measured simultaneously at the
following PiO2: 130T2.6, 91 T3.2, 61 T3.5, 42 T 3.8,
33T6.2, 24T5.2 and 16T4.2 mm Hg. In these experiments
fish had no access to the surface to breathe air.
The critical O2 tension (PcO2) was determined graphically
by the intersection of the linear regression plotted
among the decreasing values of V˙ O2 and the horizontal line
through the mean V˙ O2 values above that tension