Nichol and Somerton: Tidal stream transport of Lepidopsetta polyxystra In the eastern Bering Sea 
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ample in January, when the northern fish made vertical 
excursions with greatest frequency, it did so when tidal 
currents were southerly directed, yet the prevailing 
nighttime tidal currents were directed toward the west 
and northeast (Fig. 4). During months with frequent 
excursions, the probability of being off-bottom was not 
significantly related to current speed but was highly 
significantly related to current direction (Table 2; GAM 
(generalized additive modeling) test). Considering the 
rotary nature of the tidal current where the northern 
fish resided, the timing of vertical excursion was selec- 
tive, as opposed to random, with respect to tidal current 
direction. This selection was particularly evident during 
January when nighttime periods were sufficiently long 
to allow for two separate southerly directed currents in 
a single night. Coincident to these duel nightly southern 
currents, the fish sometimes made two separate nightly 
vertical excursions (Fig. 3A). 
Migration path 
The predicted migration path based on selective tidal 
stream transport for the northern fish extended for 
503 km and ended 0.26 km from the reported capture 
