468 
Fishery Bulletin 108(4) 
125°0'W 124°52'W 125°0'W 124°30'W 124°0'W 
Figure 1 
Location and depth (in meters) of the study area, Heceta Bank off the Oregon coast, and the area mapped 
with a multibeam sonar system in 1998 (MBARI 2201; modified from Whitmire et ah, 2008). The leftmost 
panel shows the location of the ROV transects for areas surveyed during day and night periods for each 
station (boxes) on Heceta Bank, Oregon. Global Ocean Ecosystem Dynamics (GLOBEC) track lines for light 
levels (lines 3, 3a, 4, and 4a) are shown in white dashed lines and are labeled to the right of the map. 
Depth contours are given in meters. 
broadcast-quality Sony DXC 950 three-chip color video 
camera (used for fish and habitat video analysis), a 
wide-angle low light black and white video camera, an 
obstacle avoidance sonar, a compass, three arc lights 
(250 W), four halogen lights with adjustable intensity 
(250 W), and a 10-hp cage with a separate light and 
video system (Wallace and Shepherd, 2003). One pair of 
scaling lasers (10-cm scale) mounted in parallel on the 
color video camera provided scale in the field of view of 
the video image for estimating the width of transects 
and the size of fishes and features on the seafloor. The 
distance surveyed was determined from smoothed navi- 
gation of tracklines obtained from ultra-short baseline 
tracking. Real-time audio commentary of habitat type 
and fish identification was overlaid on the videotape. 
The technical side of the ROV dive transects was man- 
aged and conducted by two four-member CSSF teams 
that worked in alternating 12-hour watches. Parallel 
interdisciplinary science teams worked in tandem with 
the ROV group to direct the scientific operations and 
ensure consistency in sampling effort. 
Day and night complements were completed outside 
the two-hour twilight periods of dawn (0436 to 0636 
PST) and dusk (2006 to 2206 PST) to avoid possible 
biases due to changes in the behavior of fishes dur- 
ing crepuscular periods (Yoklavich et al., 2000). Only 
daytime fish transects that overlapped geographically 
with, or were in close proximity to, corresponding night 
fish transects (stations 2, 3, 4, 6, and 9) were used 
in this analysis. Station 4 contained a night transect 
located approximately 1 nautical mile (nmi) away from 
the day transect but in a comparable depth range and 
over similar habitat, and therefore it was included in 
the analysis. 
A total area of 5.5 hectares along a combined total 
transect distance of 40.9 km was surveyed during 45.6 
hours (Fig. 2). Stations varied in habitat composition and 
depth (Fig. 2). Shallow areas (70-100 m) were dominated 
