Fig. 1. Experimental setup. (A) The routine swimming of zebrafish was recorded from a dorsal perspective with high-speed video. High-contrast video images were generated by illuminating the translucent floor of the aquarium with a fluorescent light, which was prevented from heating the floor of the tank by the use of a computer fan. (B) Drag was measured by tethering dead fish from the ventral surface and exposing the body to flow (see text for details).