Fabrizio et al.: Home range and seasonal movements of Centropristis striata 
89 
6 
oj 
O) 
c 
2 
CD 
E 
o 
rz 
3 
0 50 100 150 
Duration of occupancy (d) 
Figure 3 
Relationship between log e -transformed home-range size (ha) 
and duration of occupancy for 78 Black Sea Bass (Centro- 
pristis striata) of unknown sex at a reef in the mid-Atlantic 
Bight during summer-fall 2003; these fish included females, 
subordinate males, and transitional males. Duration of occu- 
pancy was calculated as the difference between release date 
and date last detected at the study site in 2003; fish were 
released between 30 May and 16 July 2003. The dashed line 
is a linear regression line provided for reference only. 
Linear changes in the probability of moving varied 
with water temperature at the bottom of the seafloor at 
station Bl; the linear decline in the likelihood of mov- 
ing was more rapid at higher water temperatures (i.e., 
temperatures exceeding 13°C; Fig. 6). These higher 
temperatures were observed at the site primarily dur- 
ing September. Generally, average water temperatures 
in fall exceeded those temperatures observed in sum- 
mer: mean temperature at the bottom of the seafloor at 
station Bl was 15.58°C (SE 0.05) in fall and 12.60°C 
(SE=0.03) in summer. 
Activity of Black Sea Bass 
For fish that did move, the random structure of the data 
for the continuous activity index was best described by 
including the variation associated with individual fish 
in the GLMM and by modeling the correlations among 
observed movements across time periods and days with 
an autoregressive moving average structure (with lag 
1). The difference in AIC between models with and 
without the random fish factor exceeded 390, indicat- 
ing that an important portion of the variation in the 
observed continuous activity index was associated with 
individual fish. Variation among individuals in activity 
levels accounted for 22-26% of the random variation 
observed during any given time period (Table 2). 
As we found when modeling the binomial 
probability of movement, activity levels of fish 
measured by the continuous activity index var- 
ied with season, time, release group, sex, and 
water temperature at the bottom of the seafloor 
at the study site (Table 2). Activity of Black Sea 
Bass decreased with decreasing differences in 
mean temperature across the site from summer 
through fall; however, the remaining main effects 
could not be interpreted directly because of the 
presence of multiple 2-way interactions (Table 2). 
Cubic time effects on activity of Black Sea Bass 
varied by season and with release group (Fig. 7) 
such that, during summer, fish released in early 
June were consistently more active than were 
fish released in late June or July. The mean pre- 
dicted activity index exhibited less variation dur- 
ing summer than during fall (Fig. 7); in summer, 
activity levels seemed fairly constant, until about 
late August (day 90 in Fig. 7), when activity lev- 
els declined rapidly. Subsequently, activity levels 
of fish were highly variable and depended on re- 
lease group: fish released in late June were more 
active in fall than were those fish released earlier 
or later (Fig. 7). 
Activity levels of Black Sea Bass exhibited 
significant linear and quadratic changes through 
time in response to mean temperature but these 
responses differed for males and fish of unknown 
sex (Fig. 8). Male fish appeared less responsive to 
temperature than fish of unknown sex, which ex- 
hibited decreasing levels of activity with increas- 
ing temperature (Fig. 8). The effect of time period on 
activity of Black Sea Bass was marginal (Table 2), but 
our modeling results indicate that fish were slightly 
more active during crepuscular periods and least active 
during the day. Consistency of the continuous activity 
index during successive days was greatest at night 
( y=0. 3297; Table 2); these responses exhibited higher 
correlations across time than did responses measured 
during other time periods. 
Discussion 
Home range of Black Seas Bass during inshore residency 
We provide the first estimates of home-range size for 
Black Sea Bass in the mid-Atlantic during their in- 
shore residency period; individuals maintained large, 
overlapping home ranges (13.7-736.4 ha), reflecting the 
spatial extent of feeding and spawning areas. Although 
fish were detected throughout the study site, most fish 
used relatively shallow areas of coarse sediments in 
the central portion of the site (Fabrizio et ah, 2013), 
indicating that the extent of suitable habitat may have 
restricted home ranges of these fish. Black Sea Bass 
that inhabit other temperate reefs in the mid-Atlantic 
region may exhibit larger or smaller home ranges, de- 
