There was an error published in J. Exp. Biol. 211, 206-214.

In the legend to Fig. 10, the sentence `Reproduced with permission (Lauder et al., 2007)' is incorrect. This error has now been removed in the online full-text version. The print version is correct.

The correct wording for the legend is:

Fig. 10. Comparison of the averaged measurements of instantaneous drag forces with the cross-flow vortex model. The steady fin measurements are also included. Blue and green data indicate tests with a 20 or 30 cm span,respectively. The inset expands the data up to an angle of attack of 20°where stall occurs in the steady case (Fig. 9) to clarify that the cross-flow vortex model does not account for viscous drag.

We apologise to the authors and readers for this error.