Turnure et al.: Patterns of intra-estuarine movement in adult Cynoscion regalis 
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sis of estuarine movement patterns, and all detections 
within an ALR before or after this 3-week period were 
included in analysis. Patterns of weakfish movement 
remained consistent even at lower temporal thresholds 
(i.e., 2 consecutive detections within 500 m), indicating 
the robustness of the ALR metric for these data. 
Calculation of the size of an ALR was made with 
the minimum convex polygon metric whereby the in- 
ner points of detection were completely enclosed by a 
minimum number of outer detection points that form a 
convex polygon. Weekly movements were calculated as 
minimum straight-line distances (in kilometers) from 
an ALR. If the original release site fell within this area, 
the release location was used to calculate subsequent 
movement distances. Otherwise, a geometric centroid 
of detections within the ALR was used. The total area 
sampled during active tracking was determined by are- 
al analysis of active tracking points and their ranges of 
detection (see Fig. 1), and by excluding areas where the 
detection ranges fell on land. ALR differs from home 
range, a strictly spatial descriptor of animal activity, 
in that ALR incorporates a temporal component (i.e., 
3 consecutive weekly detections in our study) and an 
explicit spatial component (detections within 500 m of 
one another) to describe weakfish site affinity. 
Diel movements Redetections of individual weakfish 
during diel active tracking in 2008 were first plotted 
with ArcMap 9.3 GIS software. To characterize weak- 
fish movements at the diel scale, we measured the 
minimum straight-line distance (in kilometers) across 
water of individual weakfish from an area of localized 
daytime residency (ALDR) at Deep Point in the Mul- 
lica River (Fig. 1). The location of the ALDR was de- 
termined by the previously defined seasonal ALR for 
individuals tagged in this region (see Table 1), with the 
exception of a single fish (ID 100) that did not estab- 
lish an ALR. Distances of fish from their ALDR were 
binned into 2-h increments to observe diel movement 
patterns. Nighttime was defined as the period from 1 
h before sundown to 1 h before sunrise (1930-0429 
hours) to account for potential behavioral changes 
(e.g., reproduction) related to the dusk and dawn pe- 
riods that have been identified previously in weakfish 
(Connaughton and Taylor, 1995). Daytime was defined 
as the period from 0430 to 1929 hours. We compared 
the average distance of individuals from their ALDR 
during daytime and nighttime detections using the 
nonparametric Mann-Whitney 17-test (2-tailed, a=0.05). 
Results 
Seasonal patterns of movement 
Overall patterns of estuarine movements were variable 
among individual weakfish. A majority of redetected 
weakfish (12 of 20; 60%) established an ALR within 
the study area, and some redetected fish (6 of 20; 30%) 
with sufficient redetections for analysis did not dis- 
play this localized pattern (Table 1). Of the remaining 
tagged fish, 9 fish were never redetected during active 
tracking and 2 fish were not sufficiently redetected (<3 
detections) for analysis of estuarine movements. Of 
those fish that established an ALR, the degree of use 
differed between individuals. Many of the latter fish, 
however, were detected for a majority of the time with- 
in their ALR (mean: 51% [SE 5]; Table 1). 
Weakfish established an ALR in different locations 
and habitats within the estuary. In general, 4 represen- 
tative patterns of ALRs were observed (for examples, 
see Fig. 2). These ALRs were established within subtid- 
al creeks and thoroughfares (Fig 2A; 6 of 12 locations), 
as well as within bay (Fig 2B; 2 of 12 locations) and 
river (Fig 2C; 4 of 12 locations) habitats to varying de- 
grees, and there was an association observed between 
original release site and location of an ALR (9 of 12 
fish; Table 1). The average size of an ALR (0.03 km 2 
[SE 0.01]), based on minimum convex polygon calcula- 
tions, encompassed a small proportion (0.06%) of the 
total area sampled during active tracking (48.4 km 2 ). 
Other tagged fish (6 of 29) that did not fit the criteria 
for establishment of an ALR were located within simi- 
larly localized portions of the estuary (Fig. 2D). Several 
individuals (IDs 62, 70, 103, and 162) were redetected 
for 2 consecutive weeks at locations within a range of 
0.10-1.08 km from their previous locations. 
The magnitude and duration of movements of fish 
from an established ALR differed. Several tagged fish 
(5 of 12) were observed at their ALR for 4-7 sampling 
weeks, and their final detections were at distances 
of 0.9-11.9 km from their ALR (Fig. 3A). Two tagged 
weakfish (fish IDs 140 and 155) also were observed at 
their ALR for 4 consecutive detections but were not 
detected outside that region before leaving the study 
area. One fish (ID 137) had the lowest proportion of 
potential detections within an ALR (24%; Table 1). Af- 
ter movement from the ALR, this individual was sub- 
sequently detected on 9 other occasions outside that 
region. Another small group of fish (4 of 12) were ob- 
served making excursions of varying distances (1.0-5. 9 
km) from their ALR, followed by a return after 1-2 
sampling weeks (Fig. 3B). For both groups of tagged 
weakfish, detections at an ALR frequently occurred 
during nonconsecutive sampling weeks, indicating that 
fish had potentially moved outside the sampling area 
for short (weekly) periods. Therefore, the estimate of 
fish that made excursions from these areas may be low. 
Diel patterns of movement 
Weakfish exhibited a diel periodicity of daytime res- 
idency at Deep Point (less than 0.5 km between de- 
tections; Fig. 4A) followed by nightly movements that 
began around sundown (Fig. 4B) — a finding based on 
the locations (155) of 9 individual weakfish that were 
detected by focused, intensive active tracking. For sev- 
eral individuals (n=4; IDs 64, 136, 137, and 151), their 
ALDR at Deep Point corresponded to seasonal ALR 
and original tagging location. For other fish tagged at 
