This data have been digitized from:

Peck, M. A., Buckley, L. J., & Bengtson, D. A. (2006). Effects of temperature and body size on the swimming speed of larval and juvenile Atlantic cod (Gadus morhua): implications for individual-based modelling. Environmental Biology of Fishes, 75(4), 419-429, https://doi.org/10.1007/s10641-006-0031-3

This figure shows the cod swimming speed as a function of cod length as digitized from Peck et al, 2006. You can download the data here.

The best-fit equation for the swimming speed (CSS) provided by Peck et al, 2006 (their Eq 7) is:

However, this equation causes an unrealistic increase of the swimming velocity with an increase of the larval size, as it is shown below:

Therefore, we suggest a better fit to the original data from Peck et al (2006):