Turnure et al.: Patterns of intra-estuarine movement in adult Cynoscion regalis 
175 
Table 2 
Detections and movements of tagged weakfish (Cynoscion regalis) (n= 9) tracked on a diel basis at Deep Point 
(lower Mullica River) through the use of active acoustic telemetry (from 30 June 30 to 31 July 2008). For loca- 
tions within study area and sampling points, see Figure 1. For tagging details on individual weakfish (except 
the fish (ID 100) tagged 11 June 2008 in Big Creek; 413 mm in total length), refer to Table 1. Standard errors 
of mean distances are given in parentheses. 
Fish 
ID 
First 
detection 
Last 
detection 
Number of 
tracking 
events 
detected 
Total 
detections 
(day) 
Total 
detections 
(night) 
Daily mean 
distance 
from ALDR 
(km) 
Nightly mean 
distance 
from ALDR 
(km) 
62 
July 23 
July 31 
5 
14 
! 
0.20 (0.02) 
1.24 (n/a) 
64 
July 17 
July 31 
6 
20 
4 
0.21 (0.09) 
1.10(0.21) 
100 
July 22 
- 
1 
- 
1 
- 
1.36 (n/a) 
103 
June 30 
July 30 
5 
25 
1 
0.50(0.12) 
2.27 (n/a) 
136 
July 17 
July 31 
6 
19 
6 
0.30 (0.03) 
1.49 (0.28) 
137 
July 10 
July 22 
4 
5 
12 
0.34 (0.04) 
1.24(0.25) 
151 
July 10 
July 31 
8 
24 
11 
0.28 (0.04) 
0.86 (0.13) 
162 
June 30 
July 10 
2 
2 
- 
0.53 (0.33) 
- 
204 
June 30 
- 
1 
10 
- 
0.34 (0.05) 
- 
before or after this period could not be ascertained. In- 
terpretation of diel movements (see the following sec- 
tion) further corroborates the potential influence of re- 
productive behavior on weakfish movements. 
Predator avoidance can also regulate the move- 
ments of fish species (Pittman and McAlpine, 2003) 
across varying scales but is most often discussed in 
the context of juveniles or subadults (Naesje et al., 
2012). Although predation risk is greatest for juvenile 
fishes, adult movements may also be influenced by 
such factors. Seasonal occurrences of piscivorous pred- 
ators, such as sandbar shark ( Carcharhinus plumbeus\ 
Merson and Pratt, 2005), striped bass (Morone saxati- 
lis; Ng et al., 2007), and bottlenose dolphin ( Tursiops 
truncatus; Toth et al., 2011) are common in the study 
area and may influence the movements and distribu- 
tion of adult weakfish. One manifestation of a move- 
ment strategy based on predator avoidance could be 
periodic or long-term “stationary” behavior, as docu- 
mented for Japanese croaker (Argyrosomus japonicus\ 
Naesje et al., 2012) and the consistent, localized be- 
havior observed with tagged weakfish detected weekly 
during this study for periods lasting up to 7 weeks. 
At the population level, variation in movement in con- 
trast to prolonged stationary behavior of tagged weak- 
fish, as observed in this study, could be explained by 
differences in an individual’s boldness or propensity 
for habitat exploration (Fraser et al., 2001; Frost et 
al., 2013). 
Maintenance of optimal environmental quality, es- 
pecially in dynamic estuarine environments, is another 
potential predictor of weakfish movements (Mander- 
son et al., 2014). Environmental quality, measured as 
water temperature, salinity, and dissolved oxygen, in 
relation to weakfish distribution was evaluated dur- 
ing a concurrent study, in which tagged weakfish were 
commonly detected within a relatively narrow range 
of environmental parameters near deep channel edg- 
es and emergent marsh banks and during all seasons 
(Turnure et al., in press). However, the consistency of 
detections within a narrow range of temperature, salin- 
ity, and dissolved oxygen may have been driven by a 
broader spatial restriction to the lower estuary rather 
than by directed movements to these areas within the 
estuary. 
Diel patterns 
The diel movements of tagged weakfish during this 
study could best be characterized as “commuting” be- 
haviors (Dingle and Holyoak, 2001) because they took 
place on a short-term periodic basis and likely were 
initiated in a search for spawning or prey aggregations 
followed by a return to an ALDR. Although a high per- 
centage of fish left the study area (Deep Point) used for 
examination of diel movements at night and were not 
detected until the following morning, several individu- 
als were detected in other localized areas after move- 
ment away from their ALDR. This finding may indicate 
a shift to a new nightly ALR. Alternatively, the move- 
ment of some fish outside the study area may indicate 
ranging behavior for foraging. A previous investiga- 
tion of nighttime use of subtidal creeks in the study 
area hinted at the possible use of these habitats by 
weakfish for nighttime feeding excursions on high tides 
(Rountree and Able, 1997). Initiation of movement from 
the ALDR at Deep Point (Fig. 1) corresponded to lower 
light levels and, more specifically, the nighttime cre- 
puscular period. There was high variability in move- 
ments during the early nighttime crepuscular period 
