Caudal Fin

undulation, whip!
move it east, move it west
a feathered turbine

Are you always on the go, perpetually in motion as you torpedo from one destination to the next? Your inner fish may be a tuna! Now in order to confirm this please look behind you, is your tail shaped like a double-sided scythe?

As one of the ocean’s cruising specialists, tuna possess a tail, or caudal fin, optimized for continuous and rapid travel. Generally speaking caudal fins generate thrust for fishes that move through water by undulating their bodies. The combined movement of the body and caudal region propels cruising tuna forward, launches Chinook salmon away from hangry grizzly bears, and accelerates Northern pike toward the prey they are lurking.

But not all caudal fins look the same. Tuna have lunate caudal fins that attach to the body at a narrow bridge (i.e. narrow necking) which reduces drag and maximizes thrust. In contrast, Nemo the clownfish has a round caudal fin that is attached to his body by a wide bridge. Of course Nemo isn’t traversing an ocean at rocket speeds but instead must maneuver through anemones and corals.

What fins do coral reef fish rely on to navigate through their complex habitats? I’ll save that for another tail…err…tale.