Fig. 4. Relationship between oxygen consumption, and (A) heart rate and (B) cardiac output, when Atlantic cod acclimated to 10-11°C were exposed to an acute temperature increase of 1.7°C h^-1. Open circles represent data for individual fish; filled circles represent mean values (± s.e.m.) recorded at particular temperatures. The broken lines define the linear regressions that were fitted to the individual data (heart rate: y=2.92x-18.5, r²=0.744; cardiac output: y=3.55x+16.7, r²=0.759). The solid lines are third order regressions that were fitted to the mean data to show the general trends in cardiac parameters with temperature (heart rate: y=-18.7x+0.4x²+0.0019x³+372.5, r²=0.986; cardiac output: y=-20.0x+0.7x²+0.0069x³+242.8, r²=0.995).