Cullen and Stevens: Underwater video recordings of Centropristis striata in waters off Maryland 
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Discussion 
We used our analysis of video collected with a remote 
underwater camera system to observe and count black 
sea bass, examine behavior, and distinguish between 
life stages (i.e., black sea bass with and without nu- 
chal humps) and bottom types. Our camera system 
allowed a comparison of values of MeanCount among 
sand, sand+rock, and live bottom habitats, as well as 
an examination of behavioral responses to fish traps. 
We found values of MeanCount to be significantly 
higher in live bottom and sand+rock habitats than in 
sand habitats. An important aspect of this study was 
that we were able to observe and discriminate between 
nuchal and non-nuchal black sea bass. Values of Mean- 
Count for nuchal black sea bass were positively corre- 
lated with those for non-nuchal black sea bass, which 
may be an indication that greater numbers of male fish 
were present when densities of black sea bass were 
higher. However, a method to identify individual fish 
would be necessary to avoid recounts in order to verify 
whether values of MeanCount are an adequate index 
for the number of mature males available for spawn- 
ing on different habitats. For most deployments, bottom 
types and black sea bass were relatively easy to ob- 
serve despite variability among sites in factors such as 
water depth, turbidity, and cloud cover that resulted in 
reduced visibility around the camera system. On most 
days (7 of 10), bottom visibility was -10 m or more but 
on others it was as little as -5-6 m. Low visibility as a 
factor limiting the quality of videos has been reported 
in other studies using an underwater video technique 
as a sampling method (Pratt et al., 2005; Bacheler et 
al., 2014). For example, in the south Atlantic, Bacheler 
et al. (2014) examined the influence of environmental 
factors and habitat features on trap and video detec- 
tion probabilities for reef fish and found that black 
sea bass and 2 other species were more likely to be 
observed on videos as water clarity increased. In our 
study, sampling was conducted during daylight hours 
to help ensure that natural bottom lighting was ade- 
quate. The use of artificial lighting may have increased 
visibility during periods of low light (-30% of videos in 
our study); however, our camera system did not include 
lights because it was not known if or how lights would 
affect fish behavior. 
Habitat type was the most significant factor for ob- 
serving black sea bass. This result was not surprising 
given the species strong affinity for structurally com- 
plex habitats during their inshore residency. Ross et 
al. (2016) examined fish communities on soft, natural 
hard, and shipwreck habitats near Norfolk Canyon, off 
the coast of Virginia, and observed black sea bass on 
both soft and hard bottom habitats although they were 
found primarily on the latter. Despite fish being ob- 
served on soft bottoms, Ross et al. (2016) noted that, 
like other dominant hard bottom species, they were 
generally not observed far from reef structures. In an- 
other study, Fabrizio et al. (2013) examined habitat as- 
sociations and dispersal of black sea bass with acous- 
tic telemetry at a temperate reef off the coast of New 
Jersey and found that throughout the summer and fall 
fish primarily used shallow areas (depths <27 m) with 
coarse grain materials. Similarly, we observed the ma- 
jority of black sea bass on hard and rocky bottoms at 
depths from 19 to 31 m. Conversely, despite the lack of 
bottom structure, we did observe fish on sand habitats, 
possibly because fish were attracted to the camera sys- 
tem as an additional or novel source of habitat because 
black sea bass are regularly caught by the commercial 
fishery using unbaited traps (Shepherd et al., 2002). 
Another reason for this finding may be related to feed- 
ing activities. Steimle and Figley (1996) examined diets 
of black sea bass in coastal waters off New Jersey and 
found that sandy bottom areas adjacent to artificial 
reefs were very important for feeding. They concluded 
that much of the diet of black sea bass consists of prey 
items that are not closely affiliated with reef structure. 
Lastly, the high percentage of nuchal males that we ob- 
served on sand habitats may be related to movements 
between adjacent hard bottom sites (Bacheler and Bal- 
lenger, 2015). Fabrizio et al. (2013) reported on the dis- 
persal of black sea bass from a reef off the coast of 
New Jersey and found that fish, mostly nuchal males, 
began to leave the site in early summer, possibly for 
other reef areas. 
Arrival time at a camera system may be related 
to densities of fish in the surrounding area. Ellis and 
DeMartini (1995), Willis and Babcock (2000), and Ston- 
er et al. (2008) compared the TFA of fish species in the 
camera view with their metric for relative abundance 
and found moderate to strong negative correlations be- 
tween the 2 metrics. In our study, TFA was moderately 
correlated with MeanCount for all black sea bass — a 
finding that is in agreement with results from Ellis 
and DeMartini (1995) and Willis and Babcock (2000) 
and suggests that faster arrival times for black sea 
bass are likely due to higher densities of fish in the 
area. This was the case in our study with fish appear- 
ing on cameras earlier for videos collected in live bot- 
tom and sand+rock habitats. Fish also arrived earlier 
in sand habitats when the trap was baited. 
Compared with other serranids that have been re- 
ported to primarily use their caudal fin while swim- 
ming (Fulton, 2007), the main swimming mode of black 
sea bass appeared to involve the use of both the caudal 
and pectoral fins for propulsion. In all habitats, black 
sea bass swam both with and against the current, al- 
though fish were often observed swimming close to the 
bottom and stopping or resting next to rocks or in the 
crevices of outcroppings when the current appeared 
to be particularly strong. Resting by black sea bass 
may be a type of station-holding behavior where fish 
use substrates as a refuge from flow at higher current 
speeds (Gerstner, 1998). In high-current flows, black 
sea bass might seek refuge next to or between bot- 
tom structures — a strategy that could possibly reduce 
the number observed on videos although this may not 
be the case because Bacheler et al. (2014) found that 
the likelihood of observing black sea bass on videos 
