The mechanical scaling of coasting in zebrafish (Danio rerio)

Many fish species span two or three orders of magnitude in length during the growth from larvae to adults, and this change may have dramatic consequences for locomotor performance. We measured how the performance of coasting changes over the life history of zebrafish (Danio rerio) and examined the scaling of mechanics underlying this change. Adult zebrafish coast disproportionately further and faster and maintain their speed for a longer duration than do larvae and juveniles. Measurements of drag on tethered dead fish suggest that adult fish operate in an inertial regime by coasting at relatively high Reynolds numbers (Re>1000), and in vivo drag measurements showed adults to operate with a drag coefficient (Cinert 0.024) that was consistent with previously published estimates. However, drag scaled differently at lower Re values than those assumed in previous studies. We found a viscous regime at Re