Fig. 2.

Bio-logging sensor tag-measured swim speed at mouth opening (U_open) versus estimated body lengths, both from Cade et al. (2016). All data for krill–feeding by rorquals at depth. The minimal speeds (U_min) lines are calculated from Equation (12), in the cases of the maximal net approach speeds of 1.0 m/s (dashed lines) and 1.2 m/s (continuous).