Now those of the fish which are caught as they swim out to sea are found to be rubbed on the left side of the head, but those which are caught as they swim up again are rubbed on the right side. This happens to them because as they swim down to the sea they keep close to the land on the left side of the river, and again as they swim up they keep to the same side, approaching and touching the bank as much as they can, for fear doubtless of straying from their course by reason of the stream.
Eta hona zergatik jasaten duten hori: itsasora jaitsi, ibaiertza ezkerraldera dutela jaisten dira, eta ibai gora itzultzean ertz berean mantentzen dira, erantsirik eta ahalik gehien ukituz, hain zuzen korronteagatik desbidera ez daitezen.