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Fishery Bulletin 107(2) 
56°N- 
54°N- 
Fish Release Recovery 
Northern O O 
Southern O O 
PMEL 
Mooring 
-60° N 
■58°N 
-56°N 
— 
168°W 
1 
164°W 
100 km 
1 
160°W 
168°W 
172°W 
Alaska 
164°W 
160°W 
I 
Figure 1 
Map of release and capture locations for two female northern rock sole (Lepidopsettci polyxystra) 
tagged with archival tags in the eastern Bering Sea off Alaska in 2003. The locations of the 
Pacific Marine Environmental Laboratory (PMEL) subsurface moorings where tidal current 
velocity data (speed and direction) were collected are also shown. Gray lines with numbers 
indicate the bathymetric contours (in m) in the area. 
no tidal assistance (Hunter et al., 2004a; Metcalfe et 
al., 2006). In addition to accurately determining peri- 
ods when a fish is off-bottom, successful selective tidal 
stream transport modeling also requires the ability to 
accurately predict tidal currents. 
Tidal currents over most of the eastern Bering Sea 
shelf have characteristics that offer fish a mechanism 
that assists horizontal movement. Such currents range 
from rotary motion on the central continental shelf (e.g., 
east of Pribilof Islands) to bidirectional motion along 
the Alaska Peninsula (Kowalik, 1999; Pearson et al., 
1981), and a strong semidiurnal component everywhere 
which offers fish two opportunities within a 24-h period 
to use currents to migrate in a particular direction. 
Near-bottom tidal current velocities over much of the 
eastern Bering Sea shelf average approximately 20 cm/s 
and peak to over 50 cm/s, which if used for transport, 
could provide a significant increase in migration veloc- 
ity. Moreover, the rotary nature of the currents offers 
an intriguing mechanism for transport because it can 
provide a means of transport in any direction a fish 
chooses. 
Here, we examine depth and time data from archival 
tags attached to two northern rock sole to determine 
whether vertical excursions are related to diel and tidal 
influences, and whether a simple model of selective tidal 
stream transport can be used to construct a hypotheti- 
cal horizontal migration path that is consistent with the 
observed tag release and recovery locations 
Methods 
Tagging 
Two northern rock sole were recovered from among 115 
released with attached electronic data storage tags in the 
eastern Bering Sea between 4 June and 26 July 2003. 
Release locations were approximately 200 km northeast 
of St. Paul Island in the Pribilof Islands (northern fish) 
and 18 km northwest of Unimak Island (southern fish) 
(Fig. 1). Fish were initially captured with a bottom trawl, 
tagged, and released during the course of the annual 
eastern Bering Sea bottom trawl survey (Acuna and 
