Bacheler et al.: Variation in movement patterns of Sciaenops ocellatus 
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Figure 1 
Map of study areas for red drum ( Sciaenops ocellatus) within coastal and estuarine waters of North Carolina. Left map 
shows location of coastal North Carolina (in box) along the Atlantic coast of the United States. Middle map shows view of 
entire coastline of North Carolina, with the four regions used in the movement analyses demarcated by dashed lines. The 
four regions are the following: eastern Pamlico Sound (EPS), western Pamlico Sound (WPS), Neuse and Pamlico rivers 
(NPR), and coastal and estuarine waters of southern North Carolina (SNC). The small box in the Neuse River highlights 
the location of Hancock Creek, which is enlarged in the right panel. Locations of submersible receivers in Hancock Creek 
are shown by the black dots, and the star shows where salinity measurements were taken. 
and Pamlico rivers (NPR), and 4) waters of southern 
North Carolina (SNC; Cape Lookout southward, includ- 
ing estuaries and coastal waters). These regions were 
chosen from a preliminary examination of movement 
patterns of red drum and according to natural geo- 
graphic divisions. 
The latitude and longitude of tagging and recovery 
locations were used to calculate the distance (km) and 
angle moved (measured in whole-circle bearing degrees, 
with 0° representing true north). We calculated distance 
moved both as shortest distance moved in water, us- 
ing ArcGIS 9.1 (ESRI, Redlands, CA) for distance and 
movement rate calculations, as well as straight-line 
distance (Batschelet, 1981) for circular mapping analy- 
ses. We also calculated the angle moved (in degrees) 
by each individual fish from the tagging and recovery 
coordinates (Batschelet, 1981). 
Next, we tested for the effects of fish age, region, and 
season of conventional tagging on red drum movement 
patterns. We were unable to examine the simultaneous 
influence of these three factors on red drum movement 
patterns because of low sample sizes of recovered red 
drum in some age, region, and season combinations. 
Instead, we conducted two separate statistical analyses. 
In the first, we tested for differences in days at large, 
distance moved (km), and movement rate (km/d) among 
red drum age classes and regions of tagging, using 
analysis of variance (ANOVA). Each dependent variable 
was log-transformed to reduce skewness and to homog- 
enize variability. Two-way factorial ANOVAs were used 
to test the main effects of age and region of tagging and 
their interaction at a- 0.05. To visualize these age and 
region patterns, we first constructed maps of tagging 
and recovery locations for each age class of red drum, 
using ArcGIS 9.1. We next constructed two-variable 
vector plots in Oriana 2.0 (Kovach Computing Services, 
Anglesey, Wales). The length of the bars in these circu- 
lar plots represents the straight-line distance moved by 
individual red drum, and the direction of the bar repre- 
sents the angular bearing of the fish. Separate graphs 
were made for each age class and region combination. 
We were unable to use circular statistics on these data 
because of the presence of multiple modes (Zar, 1999) 
and geographic barriers that varied by region. 
For the second statistical analysis we tested the in- 
fluence of tagging season and age class on movement 
rates of red drum. Age was also included as a variable 
in this analysis because of its potential influence on 
seasonal movements. Only red drum recovered within 
60 days of tagging were included in this analysis so 
that fish could be classified accurately into a seasonal 
period, and the midpoint of time at large for each fish 
was used to determine its season of recovery. Seasonal 
periods were classified as spring (March-May), summer 
(June-August), fall (September-November), and winter 
(December-February). Differences in log-transformed 
movement rates by season and age class were tested 
with a two-way factorial ANOVA. 
To visualize this seasonal effect, stacked and stepped 
histograms of distance moved and directionality were 
