A slim banded fish that is almost never seen alone: it travels at the snout or flank of a shark, a ray, a turtle or a drifting log, matching every turn, and if the host leaves it goes with it.
The position is physics, not courage. A large swimming animal pushes a pressure wave ahead of it, and a fish riding that wave is carried along at a fraction of the effort - the same trick a cyclist uses behind a truck. That is the main payment; the scraps from the host's meals and the parasites picked off its skin are a bonus rather than the point.
What the host gets is debated and probably very little. Sharks tolerate the escort rather than benefit from it, and pilot fish do not appear to clean enough to earn their keep.
Juveniles do the same thing with jellyfish and floating weed, which is where the young of a great many open-ocean fish spend their first months: a drifting object is the only structure in a habitat that otherwise has none. Old accounts of pilot fish guiding ships across oceans describe exactly this, with the hull as the host.
The species. Naucrates ductor (Linnaeus 1758) - leader (see genus). ETYFish
- slim silver-white fish crossed by five or six broad dark vertical bands
- swims immediately ahead of or beside a larger animal, matching its speed exactly
- keeps station in the pressure wave at the host's snout
- length up to 70 cm
