Fig. 8. Mean propulsive wavelength () versus fork length (FL) for individual chub mackerel at 18 °C (open squares) and 24 °C (filled squares). Because there was no significant effect of speed on , the mean of the propulsive wavelengths at all swimming speeds was calculated for each individual. Error bars represent ±1 S.E.M. The lines are the best-fitting linear regressions: =1.11FL-1.32, r²=0.89, N=9, P<0.001, at 18 °C (dashed line); =1.09FL+1.32, r²=0.83, N=12, P<0.001, at 24 °C (solid line). Mean increases with FL at the same rate at the two temperatures but, at a given FL, is significantly greater at 24 than at 18 °C (ANCOVA, P=0.0024).