Fabrizio et al. : Home range and seasonal movements of Centropristis striata 
95 
0.5 
>% 
| 0.0 
o 
< 
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0 
=6 - 0-5 
0 
Q. 
C 
0 
0 
S - 1.0 
-1.5 
- 2-10 12 2 
Mean water temperature at B1 (standardized) 
Figure 8 
Mean predicted activity levels from the generalized linear 
mixed model for male Black Sea Bass (Centropristis striata) 
(filled circles, solid line) and fish of unknown sex (squares, 
dashed line) at a reef in the mid-Atlantic Bight; the activity 
index is presented in log e -transformed units. Mean daily wa- 
ter temperature at the bottom of the seafloor was measured 
in degrees Celsius at acoustic station B1 (see Fig. IB) from 
30 May to 6 November 2003 and was standardized to a mean 
of 0. Quadratic regression lines are shown for reference only. 
frequented by fish during the day and that movements 
to and from feeding areas are not far ranging. Although 
adult Black Sea Bass use reefs for shelter, they do not 
depend exclusively on reef fauna for prey (Steimle and 
Figley, 1996). In New Jersey coastal waters, Black Sea 
Bass primarily consume juvenile Atlantic rock crabs 
( Cancer irroratus ) and other invertebrates typically 
associated with nearby sandy sediments (Steimle and 
Figley, 1996; Murdy et ah, 1997). 
Across successive days, we observed greater consis- 
tency in mean activity levels at night than during any 
other time of the diurnal period. Black Sea Bass are 
believed to spawn at night (McGovern et al., 2002), 
and, at the study site, movements during night were 
less variable than movements observed during other 
times of the day. Consistent nightly activity levels of 
Black Sea Bass at the study site indicate that if fish 
spawn at night, spawning may occur near areas used 
for feeding and shelter. Our acoustic studies of Black 
Sea Bass movements and activity levels are indica- 
tive but cannot address small-scale changes in position 
associated with complex behaviors and interactions 
among individuals. For example, social hierarchies 
may be maintained by dominant males patrolling or 
defending territories and by females sampling these 
territories. Other approaches, such as the use of mobile 
acoustic telemetry or fine-scale acoustic position- 
ing systems, are better suited for investigation of 
these hypotheses. 
Conclusions 
During their inshore residency, Black Sea Bass 
in the mid-Atlantic region maintained large 
but highly variable home ranges. Home ranges 
of females, subordinate males, and individuals 
transitioning to males depended on the dura- 
tion of occupancy at the study site, whereas the 
home range of mature males varied with release 
group (i.e., groups of fish tagged in early June, 
late June, or July). Among these mature males, 
the probability of movement (>400 m) and mean 
activity level also varied with release group. 
Groups of Black Sea Bass exhibited distinct be- 
haviors that may potentially affect growth and 
reproduction through effects on home-range size. 
Specifically, mature males released early in the 
study period may have arrived earlier at the in- 
shore reef and established and maintained larger 
home ranges than males arriving later in sum- 
mer. Our acoustic study is the first to indicate 
the existence of behavioral groups among wild 
Black Sea Bass. The use of an activity index 
that gauged movements on the order of 400 m 
revealed that Black Sea Bass were most active in 
summer and activity levels in other seasons were 
lower and more variable in comparison. Seasonal 
differences in activity among groups of Black Sea 
Bass may have resulted in differential vulnerability to 
exploitation by passive gears, particularly for mature 
males in fall. Additional studies with large numbers of 
fish are required to elucidate the composition of behav- 
ioral groups and the role of subordinate males, transi- 
tional males, and females in the maintenance of group 
behaviors. 
Acknowledgments 
We thank D. Mountain and M. Taylor (NOAA Fisher- 
ies, Woods Hole, MA) for loaning us the conductivity, 
temperature, and depth sensors and providing tech- 
nical assistance and the NOAA scientists and volun- 
teers who assisted with at-sea operations. Vessel sup- 
port was provided by S. Sirois (RV Gloria Michelle ), R. 
Haner (RV Gloria Michelle ), W. Ihde (MV Samantha 
Miller ), E. Christman (NOAA vessel Thomas Jefferson ), 
C. Brown (RV Nauvoo), J. Hughes (RV Walford ), and R. 
Alix (RV Loosanoff). We thank 2 anonymous review- 
ers whose suggestions helped clarify the presentation 
of this work. This study was funded by the U.S. Army 
Corps of Engineers and was conducted in accordance 
with guidelines concerning the use of animals in re- 
search published by the American Fisheries Society 
