Depth data from archival tags on northern rock sole (Lepidopsetta polyxystra) were examined to assess whether fish used tidal currents to aid horizontal migration. Two northern rock sole, out of 115 released with archival tags in the eastern Bering Sea, were recovered 314 and 667 days after release. Both fish made periodic excursions away from the bottom during mostly night-time hours, but also during particular phases of the tide cycle. One fish that was captured and released in an area of rotary currents made
vertical excursions that were correlated with tidal current direction. To test the hypothesis that the fish made vertical excursions to use tidal currents to aid migration,
a hypothetical migratory path was calculated using a tide model to predict the current direction and speed during periods when the fish was off the bottom. This migration
included limited movements from July through December, followed by a 200-km southern migration from January through February, then a return northward in March and
April. The successful application of tidal current information to predict a horizontal migratory path not
only provides evidence of selective tidal stream transport but indicates that vertical excursions were conducted
primarily to assist horizontal migration
