Fig. 6. In vitro haemoglobin concentrations in the cod blood used to generate the haemoglobin-oxygen binding curves presented in Fig. 5. For the 20 or 24°C experiments, temperature was increased from 7°C (acclimation temperature) to these temperatures over a 1 h period. Haematocrit was initially set at 20%, and changes in P_O2 were made every 30 min. Values are means ± s.e.m. (N=5-6). A two-way ANOVA revealed that haemoglobin levels at 24°C were significantly (P<0.05) lower than measured at the other two temperatures.