To assess the extent and nature of the impacts on glass sponges and associated community, we collected video and still imagery along fixed transects using a Remotely Operated Vehicle (Phantom ROV HD2 + 2, Deep Ocean Engineering) twice a year for four years following cable installation. Our study followed a 2-way (treatment × time) design. Transect locations were chosen by overlaying the reef perimeter mapped by the Canadian Hydrographic Service using multibeam bathymetry data (K. Conway, Natural Resources Canada) and cable crossing locations provided by the BCTC. Three cable transects followed the three cables crossing the reef polygon. Control transects were plotted parallel to cable transects at a distance of approximately 100 m (Fig. 1). Cable transects were 108 ± 23.6 m and control transects were 125 ± 7.4 m long (mean ± SD, n = 3). Three 2 × 2 m index sites were randomly chosen along each transect and each marked with two numbered hard trawl floats (diameter 95 mm) attached to iron weights and carefully positioned between the living glass sponges. Cable index sites were laid out in a way that the cable ran through the middle of each site. The resulting six transects and 18 index sites were surveyed twice a year, in spring and fall, between October 2008 and February 2012.