*2.2. Video Transect Surveys as an Assessment of Reef Fish Abundance*

Some reefs are known to have more abundant and diverse reef fish communities, and we suspected that this may affect how structures are used across a reef tract. We therefore began by establishing a baseline of abundance across the 8 sites. To evaluate the overall abundance and diversity of reef fish species within the functional feeding guilds present at the 8 sites, 8 videos (~3–4 min) were captured along each of the perpendicular 30 m transects (2 videos per transect) between the hours of 900 and 1500. A diver swam the length of the transect while holding a PVC camera frame with 2 forward-facing GoPro cameras attached at heights of 30 cm and 100 cm above the substrate, so as to capture both benthic and mid-water fish species. Each video was analyzed to identify both the fish species present and any behavioral interactions with the substrate including, but not limited to, using substrate for shelter or as a food resource. Fish species were classified into one of four functional feeding guilds (Table S1): herbivores, omnivores, invertivores, and piscivores [25,29,47]. Analysis of fish feeding guilds has been found to be adequate for comparing reef fish community structures and can distinguish functionally diverse communities from seemingly diverse communities that have functional redundancy [48–50]. Although fish of the family Haemulidae are omnivores, they were separated into their own functional feeding guild—invertivores—because of their nocturnal feeding activities and daytime use of the structure for rest.
