The ROV was equipped with a forward-facing video camera
(Sony EVI-330 standard definition NTSC with over 460 TV lines
resolution; oblique angle adjusted based on bottom slope) and
downward-facing photo camera (C-MAP Cyclops still camera system).
During each survey, the ROV first flewalong the total length of
each transect approximately 1 m above the benthos and captured
video (continuously) and still images (every 15 s). The ROV then
returned to the index sites (tracked with a Trackpoint 3 ultra-short
base line acoustic tracking system) and captured a series of overlapping
still images of the areas between the markers. Each image
was 8 megapixels and covered 1.1 ± 0.29 m2 of substrate
(mean ± SD, n ¼ 78). All images had laser projection dots 10 cm
apart for scale, from a pair of parallel lasers mounted inside the still
camera housing. During all ROV dives, the navigation software
continuously recorded date, time, depth, and ROV position. During
the October 2010 survey a Hydrolab minisonde CTD with
temperature and salinity sensors was mounted onto the ROV to
collect additional environmental data at 30 s intervals.