Fig. 5. A theoretical estimate of the venous oxygen delivery to the heart via the cardiac circulation for cold- and warm-acclimated rainbow trout (see Discussion for an explanation of the derivation of the oxygen-delivery curves). The filled squares (cold-acclimated rainbow trout) and circles (warm-acclimated trout) represent the venous oxygen delivery at the measured venous blood oxygen partial pressures for rainbow trout under resting conditions and at 100% critical swimming speed (U_crit) with cardiac output () at the routine levels indicated. Because cardiac output would have increased at U_crit, the curve underestimates the true venous oxygen delivery. The open symbols, which account for the effect of a 2.1-fold increase in , indicate that the increase in would have restored venous oxygen delivery for both cold- and warm-acclimated fish. 1 torr=133.3 Pa.

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