4 
Fishery Bulletin 113(1) 
gimes to maximize fine-scale data acquisition within 
the constraints of tag memory capacity and battery life. 
In 2008, Cefas G5 DSTs were programmed to record 
depth (0.15 m resolution) every 2 min and temperature 
(0.1°C resolution) every 4 min. In 2009, Cefas G5 long- 
life DSTs stored depth and temperature records every 
2 min, and tags in 2010 recorded depth at 1-min inter- 
vals and temperature every 2 min. Time-series data for 
cumulative analyses were standardized to a sampling 
regime of 2-min intervals for depth and 4-min intervals 
for temperature for all tag recoveries. 
Upon recovery, fine-scale depth and temperature 
data were downloaded from all DSTs and complete 
time-series records over the entire deployment period 
were recovered from 22 DSTs. Battery life expired 
before recovery of 11 DSTs; however, the time-series 
data for the active recording life of these 11 DSTs 
were retrieved and provided by the tag manufacturer 
(Cefas Technology Limited). Four of the internally im- 
planted DSTs were either shed through the incision 
site or incidentally discarded along with the viscera 
during fish processing, as only conventional identifica- 
tion markers were reported by fishermen Subsequent 
investigations should incorporate 3 recovered data 
sets because recaptures were reported after comple- 
tion of comprehensive data analyses, and 1 DST was 
lost in the mail. 
Data analysis 
Time-series data were formatted in Excel worksheets 
before export into an Access database (Microsoft Of- 
fice 2010, Redmond, WA). All records were classified as 
day , night , or twilight values on the basis of the mean 
monthly time (Pacific Standard Time [PST]) of sunrise, 
sunset, and nautical twilight at the initial tagging loca- 
tion from the Astronomical Applications Department of 
the U.S. Naval Observatory data services portal (http:// 
aa.usno.navy.mil/data/index.php). Daytime was defined 
as the average monthly time of sunrise until the aver- 
age time of sunset; nighttime was assigned to all val- 
ues between the mean time of nautical twilight at dusk 
until the mean time of nautical twilight at dawn; and 
twilight values included all data between mean time of 
sunset and nautical twilight at dusk as well as from 
nautical twilight at dawn until mean time of sunrise 
for each month. 
Vertical rate of movement (VROM) was calculated 
for each fish (n= 33) as the absolute difference of all 
subsequent records of depths taken every 2 min. In- 
dividual VROM values were converted to m h -1 before 
subsequent analyses. For all fish, VROM values that 
exceeded 150 m Ir 1 were binned by hour of the day to 
further evaluate daily periods of peak vertical activity. 
Depth values <5 m were binned by month and by hour 
to identify periods of surface-oriented behavior. Analy- 
ses did not control for autocorrelation in the mean com- 
parisons and descriptive statistics used to characterize 
vertical data by time of day and season. 
Seasonal depth statistics were evaluated for the 16 
individual fish for which time-series data was collected 
for each month of the calendar year. Daily depth and 
temperature means were calculated and plotted with a 
7-day running mean for smoothing. Daily depth prob- 
ability plots were constructed with Matlab software 
vers. 6.0 [R12] (The MathWorks, Inc., Natick, MA) for 
each month with depth bins of 1 h by 2 m to illus- 
trate the cumulative probability of occurrence for each 
depth. Spectral analysis by use of the fast Fourier 
transform (FFT) algorithm was conducted to show the 
diurnal signal and associated harmonics dominating in 
the frequency range of 0. 5-8.0 cycles per day (cpd), and 
a Hanning window was used to reduce overlap between 
adjacent spectral peaks (Shepard et ah, 2006). Data on 
mean daily depths were used to remove the diurnal 
cycle before long-period oscillations in the frequency 
band of 0.02-0.14 cpd were calculated for the 3 longest 
time series (721-741 days). 
A paired /-test was conducted from mean depth val- 
ues of 16 data sets that contained time-series records 
for each month of the calendar year to determine if 
seasonal differences were apparent between winter 
months (October-March) and summer months (April- 
September). Paired /-tests were also employed for all 
white seabass in- 33) to identify differences in VROM 
values: daytime versus nighttime periods, daytime 
versus twilight periods, and nighttime versus twilight 
periods. All mean values are indicated as means with 
standard deviations (SD) in parentheses, and a<0.05 
was used to infer significance. 
Results 
Tag deployments and recoveries 
Between April 24, 2008, and June 8, 2011, 173 adult 
white seabass, ranging in size from 71 to 152 cm TL 
(mean=118 cm TL), were affixed with DSTs. Of the 95 
individuals for which sex was determined during tag- 
ging, 76% were identified as females and 24% were 
sound-producing males. Commercial and recreational 
crews recaptured 41 tagged individuals (77% female) 
during the study period, an overall recapture rate of 
24% (Table 1). Annual recapture rates varied from a 
low of 6% (1 of 17) for 2011 deployments to a high of 
29% (17 of 58) for 2010 deployments. Collectively, the 
largest number of tag recoveries also occurred in 2010, 
with 17 of the 41 tag recoveries (41%) reported during 
that year. Between the months of April and October, 
95% of tag recaptures occurred. Of the 41 recaptured 
individuals, 13 were harvested by California gillnett- 
ers, 3 were reported by Mexican gillnetters, 13 were 
taken by California commercial hook-and-line vessels, 
5 were caught by California recreational anglers, and 7 
were recovered by California spear fishermen (Table 1). 
Collectively, 9130 days of time-series data compiled 
from 33 DSTs provided 6.30xl0 6 depth and 3.65xl0 6 
