436 
Fishery Bulletin 113(4) 
Figure 2 
Percentages of different initial orientations of yellowtail flounder ( Limanda ferruginea ) on or in the 
substrate in relation to the center of the footgear of a bottom trawl as observed in analysis of video 
footage from 5 trawl tows conducted in June 2010 on the southern Grand Bank off eastern Newfound- 
land. Orientations were related to the trawling direction, represented in the figure by the arrow. Indi- 
viduals were categorized as on the (A) port or (B) starboard side or as in the (C) middle of the trawl. 
The following number of observations of fish in the 3 categories were used: 46 on the port, 47 on the 
starboard, and 97 in the middle. The striped areas indicate fish that were assumed to have been herded 
previously by the sweeps. 
20 to 52 cm. The majority of yellowtail (60-75%) were 
observed to be resting in or on the substrate in the 
video footage before they reacted to the footgear, while 
the remainder were observed swimming into the field 
of view. Yellowtail observed swimming into the frame 
rather than resting in or on the substrate in the video 
footage displayed behaviors (run, slope, and rise) simi- 
lar to those of the fish recorded in this study. 
Orientation 
Orientation of yellowtail before their initial reaction 
to the central footgear varied, depending on where in 
the trawl mouth an individual originally was observed 
(Fig. 2), and orientation was found to be nonrandom, 
being significantly clustered, for run, slope, and rise 
behaviors (Rayleigh test, P<0.001). Most individuals in 
peripheral locations faced inward; 46% and 51% for in- 
dividuals on the port and starboard sides (Fig. 2, A and 
B). Most individuals in the middle of the trawl mouth 
faced the vessel, away from the oncoming trawl (46%, 
Fig. 2C). 
Initial response 
None of the observed individuals displayed an initial 
behavior of pass under or hop. Most individuals (112 
of 150 fish) had an initial response of run, and only 
9 individuals were observed to initially rise. The ma- 
jority of individuals (91%) swam in the direction in 
which they were oriented on the substrate. Location, 
fish length, gait, and start density alone did not have 
a significant influence on the initial herding responses 
of run and slope, but swimming direction significantly 
influenced each of those 2 responses (Table 3; Fig. 3). 
Most individuals that initially responded with slope 
behavior swam perpendicular to the trawling direction 
(79%), and individuals that exhibited a run response 
were twice as likely to swim in the trawling direction 
as fish that responded with slope behavior (42% versus 
21%). Fish that initially responded with rise behavior 
did not have a 2-dimensional swimming direction; in- 
stead they propelled off the seabed vertically and past 
the height of the footgear. Individuals that were herded 
(with run and slope behavior) spent 3-4 times longer 
