The native freshwater fish fauna of the Hawaiian Islands is composed of four gobiid species and one eleotrid. All five species are amphidromous. They spawn in freshwater, go to sea as free embryos and, as juveniles (sometimes referred to as post-larvae), enter fresh water again. Juveniles of two of these species, Awaous guamensis and Sicyopterus stimpsoni, had been observed maintaining directed migratory activity in the absence of water flow during the early freshwater phase of their upstream migration. Our experiments demonstrate that these juveniles are strongly attracted to flowing water. But, when water flow stops the fish persist in migratory behaviour in the same compass direction even when the tank is rotated, controlling for local landmarks and chemical cues, or when the trap that was the original water source is moved. This indicates a rapid (10 min or less) learning of directional cues. Preliminary data indicates a similar ability in a third species, Lentipes concolor. Rapid acquisition of directional preferences may be critical during upstream migration, when these tiny fish traverse water falls and other barriers by climbing in intermittent water flows. We suggest that rapid directional learning may have evolved in gobies as part of their predator avoidance repertoire and been subsequently applied to migration in streams.