Graves et al.: Use of archival tags to study postrelease survival of and habitat use by estuarine and coastal fishes 
375 
Figure 1 
X-tag (Microwave Telemetry, Inc., Columbia, MD) attached to a striped bass ( Morone 
saxatilis). The nylon intramuscular tag anchor was inserted approximately 5 cm 
towards the dorsal midline, an area where the anchor had a high likelihood of 
securely interlocking with the pterygiophores supporting the dorsal fin spines. 
line (Momoi Fishing Co., Ako City, Japan) attached to a 
large, hydroscopic, surgical-grade nylon intramuscular 
tag anchor according to the method of Graves et al. 
(2002). Attachment assemblies were implanted with 
a 5-cm stainless steel applicator attached to a 0.3-m 
tagging pole that was inserted behind a scale approxi- 
mately 5 cm deep into a target region approximately 
6 cm posterior to the origin and 5 cm ventral to the 
base of the dorsal fin (Fig. 1). In this region, the nylon 
anchor can pass through and potentially interlock with 
pterygiophores supporting the dorsal fin well above the 
coelomic cavity containing visceral organs (Graves et 
al., 2002). 
Data analyses 
Net movement was calculated as a minimum straight 
line distance (MSLD) traveled between coordinates of 
initial tagging and coordinates of the first reliable sat- 
ellite transmission by using Argos location codes 1, 2, 
or 3 (Horodysky et al., 2007). Archived and transmitted 
point measurements of depth and temperature recorded 
by PSATs were summarized in 5-m and 1°C interval 
histograms. Data sets were truncated to remove records 
before tagging and after PSAT pop-up. 
To assess potential diel differences in habitat utiliza- 
tion, mean depths and temperatures were generated for 
each diel period (day, night) of each tracking day (n = 30) 
for each of the eight striped bass. Diel period designa- 
tions were based on times of local sunrise and sunset; 
crepuscular periods (30 minutes on either side of dawn 
and dusk) were eliminated from all diel analyses. Diel 
differences in the depth and temperature means were 
assessed separately with linear mixed effects models of 
the following form (Pinheiro and Bates, 2004): 
Y pi=H + T p + a i + £ pi’ (1) 
where p = the overall mean depth or temperature; 
x = the fixed effect of diel period p; 
a t = the random effect due to individual fish; and 
e • = error terms. 
Application of linear models requires satisfying three 
assumptions: independence and normality of the response 
within and among samples, and homogeneity of vari- 
ances among all levels of the fixed effects (Underwood, 
2002). However, PSAT data constitute repeated noninde- 
pendent observations within individual fish and may fail 
to satisfy the assumptions of normality and homogeneity 
of variance. Accordingly, a repeated measures form of 
Equation 1, including a Box-Cox transformation of the 
depth and temperature data, rectified these problems 
in the striped bass data. To characterize the within- 
individual autocorrelation, several candidate covariance 
structures were fitted to the transformed depth and 
temperature data, and the appropriate structure was 
selected by using Akaike’s information criterion ( AIC ): 
AIC = -21n(L) + 2p, (2) 
