94 
Fishery Bulletin 112(1) 
in other seasons. Similarly, mean activity levels 
of Black Sea Bass were highest during summer 
and declined significantly in the fall, regardless 
of time of day. Throughout the summer, fish main- 
tained high mean activity levels that were fairly 
constant. 
Seasonal declines in activity of Black Sea Bass 
also were observed among 14 Black Sea Bass held 
in captivity from July through December of 2002 
in a 121,000-L research aquarium. In these cap- 
tive fish, aggressive behaviors were highest soon 
after dominant males established territories in 
summer, and these behaviors declined over time. 8 
Our field-based observations of lower mean activ- 
ity indices in the fall are consistent with a de- 
cline in aggressive pursuits and establishment of 
stable territories. Although laboratory and field 
experiments yielded analogous results, the spa- 
tial scales of these studies were vastly different. 
Additional studies at the scale investigated at 
the HARS but with the ability to identify spe- 
cific movement behaviors (e.g., foraging, evasion, 
searching) are necessary to determine the nature 
of seasonal changes in activity levels of Black Sea 
Bass. 
Among Black Sea Bass in the mid-Atlantic, the 
probability of undertaking seasonal movements 
on the order of 400 m varied among groups of 
fish and depended on sex and other factors. For 
example, on the basis of the binomial movement 
index, we observed that mature males that re- 
mained at the study site after October were more 
likely to move than were fish of unknown sex that were 
present at that time. During that time, that group of 
males may have been more vulnerable to capture by 
passive fishing gear. Similarly, differences in seasonal 
movements unrelated to fish size were observed among 
release groups of male fish (Fig. 5A). On the basis of 
our observations, we postulate that Black Sea Bass 
arrive and establish residence at mid-Atlantic reefs 
throughout the summer; furthermore, groups of fish 
within these resident populations exhibit diverse sea- 
sonal movement patterns. Variations in movement pat- 
terns within a population are not likely to be the result 
of random movements among individuals; instead, such 
variations have been postulated to represent behavioral 
differences that may contribute to niche specializations 
(Hammerschlag-Peyer and Layman, 2010). Further 
research is necessary to elucidate factors that contrib- 
ute to the formation and maintenance of behavioral 
groups in Black Sea Bass, including factors associated 
with the complex social behaviors exhibited by this 
species. 
Fabrizio, M. C., J. P. Pessutti, J. P. Manderson, A. F. Drohan, 
and B. A. Phelan. 2005. Use of the Historic Area Remedia- 
tion Site by black sea bass and summer flounder. Northeast 
Fish. Sci. Cent. Ref. Doc. 05-06, 95 p. [Available from Na- 
tional Marine Fisheries Service, 166 Water St., Woods Hole, 
MA 02543-1026.] 
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Time (days) 
Figure 7 
Mean predicted activity levels from the generalized linear 
mixed model for 3 groups of Black Sea Bass ( Centropristis 
striata) released at a reef in the mid-Atlantic Bight in early 
June (filled circles), late June (squares), and July (crosses); 
the activity index is presented in log^-transformed units and 
the data span the period from 30 May (time=0) to 6 Novem- 
ber (time=161) 2003. 
Diel activity of Black Sea Bass 
In some species, activity patterns are associated with 
environmental light levels (Lpkkeborg et al., 2000) and 
may be mediated by temperature (e.g., Hurst and Duffy, 
2005), nutritional state (Metcalfe et al., 1998), or other 
factors (Reebs, 2002). We observed declining activity 
levels (number of times a fish moved >400 m during 
a 3-h period) of Black Sea Bass as temperature differ- 
ences across the study site decreased. However, indi- 
vidual fish exhibited highly variable activity levels (as 
measured by the continuous activity index) that were 
not explained by factors we considered in this study, 
indicating that age, physiological condition, social sta- 
tus, or other individual-based characteristics mediated 
activity levels. Additionally, interspecific interactions 
and the distribution and availability of prey resources 
likely contributed to observed variations in activity. 
Differences in activity levels of Black Sea Bass dur- 
ing crepuscular, daytime, or nighttime periods were 
less striking than during different seasons. The mean 
activity index observed during the daytime tended to be 
lower than mean indices observed during crepuscular 
periods or at night. Black Sea Bass, which are visual 
feeders, feed during daylight (Steimle and Figley, 1996), 
and low activity levels at this time may indicate that 
fish feeding areas may be located near (-400 m) areas 
