10 
Fishery Bulletin 1 13(1) 
Upon harvest, 77% of recaptured individuals were 
identified as female, indicating that white seabass sex 
can be adequately determined on the basis of the detec- 
tion of sound production during the spawning season. 
The skewed sex ratio of 3. 1:1.0 observed in this study 
may be related to temporal or size-related segregation 
among sexes; however, practical inferences cannot be 
made without a suitable sex-ratio estimate for the wild 
population. 
Vertical movements 
The observed shift of white seabass to deeper waters 
during the winter months may be in response to de- 
creased thermal stratification or possibly to the in- 
terrelated effects that these conditions have on prey 
distribution and availability. As reported for other spe- 
cies, multiple factors, such as changes in oceanographic 
conditions and prey distribution, contribute to the ver- 
tical movements displayed by a species 
at different times and locations (Hinke 
et ah, 2005; Shepard et ah, 2006; Schae- 
fer et ah, 2007; Sepulveda et al., 2010). 
Annual cycles of surface productivity 
and temperature structure off the coast 
of California have been shown to influ- 
ence the vertical distribution of Chinook 
salmon ( Oncorhynchus tshawytscha), 
with deeper profiles documented during 
the winter months (Hinke et ah, 2005). 
Seasonal shifts in vertical distribution 
have also been described for Atlantic cod 
( Gadus morhua) (Neat et ah, 2006) and 
yellowtail flounder (Limanda ferruginea ) 
(Walsh and Morgan, 2004) in the north- 
west Atlantic. 
Given the interannual variability in 
the depth and temperature profiles ob- 
served for multiple tagged individuals 
(Fig. 3, A and B), it is likely that seasonal 
trends in vertical distribution are closely 
related to localized oceanic conditions. 
Interannual variation between consecu- 
tive winter seasons was evident from the 
723-day track of fish A03595, which tran- 
sitioned from a mean depth of 31.8 m (SD 
13.2) in the winter months of 2009-2010 
to a mean depth of 8.4 m (SD 3.6) during 
the winter months of 2010-2011. Simi- 
larly, 5 tracks that extended throughout 
the winter months of 2010-2011 exhib- 
ited a considerable reduction in mean 
depth (18.4 m [SD 7.3]) compared with 
the 6 tracks recorded in the winter of 
2008-2009 (30.8 m [SD 13.0]), but mean 
temperature values remained consistent 
(12.8°C) for both sets of time-series data. 
Spectral peaks at 1 and 2 cpd may 
represent increased vertical movements 
around dawn and dusk, and harmonic peaks at 3 and 
4 cpd may indicate weaker movement patterns sur- 
rounding daily tidal fluctuations (Fig. 5A). Periodic os- 
cillations in the vertical thermal gradient within the 
coastal waters off San Diego have been shown to cycle 
at 6, 8, 12, and 24 h (1, 2, 3, and 4 cpd) relative to in- 
ternal tidal fluctuations (Cairns, 1968), which typically 
lag 3 to 5 h behind mixed semidiurnal surface tides 
(Cairns and LaFond, 1966). Therefore, consistent daily 
shifts in depth distribution of white seabass may corre- 
spond with semidiurnal fluctuations in coastal thermo- 
cline depth. Diel and circatidal rhythms in the vertical 
movement patterns of basking sharks ( Cetorhinus max- 
imus) also were identified in the northeast Atlantic on 
the basis of spectral peaks in fine-scale depth records 
at periods of 1 and 2 cpd (Shepard et ah, 2006). In the 
study described here, inconsistent harmonics in longer 
period (0.02-0.14 cpd) spectral density plots (Fig. 5B) 
indicate that the time-series data did not continuously 
