Somerton et al: Quantifying the behavior of fish in response to a moving camera vehicle 
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Figure S 
Variation in (A) group speed, (B) mean individual speed, (C) swimming polarity, and (D) nearest 
neighbor distance (NND) for a school of vermilion snapper ( Rhomboplites aurorubens ) in the 
northeast Gulf of Mexico in 2014 is shown for the disturbed time period, the 22-s period from 
passage of the tow vessel to 1 s before entry of the camera vehicle into the benthic camera field 
of view. The horizontal lines represent the mean (solid) and 95% confidence intervals (dashed) 
of each school descriptor during the undisturbed period, the 10-s period taken 20 min after the 
previous vessel passage. The closest approach of the vehicle was at 23 s, and the vehicle velocity 
was 1.5 m/s; therefore, the approximate distance in meters of the vehicle to the fish school can 
be calculated as (23-0x1.5, where t is the time in seconds after vessel passage. 
We emphasize that the fish response to a camera 
vehicle during a single pass should not necessarily be 
i considered typical because there are a variety of fac- 
tors that could have been influential. First, stimulus 
| detection by individual fish or the school may vary 
! with environmental conditions. For example, detec- 
tion of visual stimuli will be diminished in turbid or 
low-light conditions. Second, the behavioral response 
j to a given level of stimulus may vary with previous 
[ experience of such stimuli. A response to vessel noise, 
| for example, may be less in areas with high vessel 
traffic because of acclimatization to stimuli. Third, the 
| behavioral response to a given level of stimulus may 
| vary with the perceived level of predatory threat. For 
example, an avoidance response may be inhibited in 
complex habitats that provide nearby refuge. Conse- 
quently, we expect behavioral responses to be varied 
and recognize that considerable additional field stud- 
ies will be needed to provide realistic predictions of 
behavioral responses to stimuli produced by moving 
camera vehicles. 
We deemed the 10-s interval that occurred 5 min 
before passage of the tow vessel to be indicative of the 
values of the school and individual fish descriptors 
during an undisturbed state. However, the school had 
previously experienced the disturbance created by the 
setting of the benthic cameras and 2 prior passes of the 
towed camera system; therefore, an undisturbed state 
should be considered in a relative sense. Our qualita- 
tive observations of the behavior of vermilion snapper 
toward the benthic cameras indicate that the school 
returned to fairly calm behavior within a few minutes 
